Patent Description:
Radiation field amplifier systems showing the aforementioned features are known from the prior art.

<CIT> provides a laser light source with a holder, bodies of which have a rip. <CIT> relates to a laser amplifying system in which a solid state disc is clued to a cooling body. <CIT> provides fabrication technics to form a multi structured monolithic cavity that generates a single axial mode of laser operation.

It is the object of the present invention to improve an operation of a radiation field amplifier system.

This object is solved by a radiation field amplifier system according to claim <NUM>.

One advantage of the present invention has to be seen in the fact that a heat conductance between said amplifying unit and said one heat spreading element or said at least one heat spreading element is increased and accordingly an efficiency of cooling of said amplifying unit by said heat dissipation system is increased.

Due to the increased cooling efficiency, amplifying units with higher heat losses can be used in said radiation field amplifier system and the efficiency of said radiation field amplifier system is increased.

Another advantage of the present invention is that an interface between said amplifying unit and said one heat spreading element or said at least one heat spreading element, which is pressed against said amplifying unit, is smoother and distortions between said amplifying unit and said heat spreading element are reduced.

With respect to said radiation field no further details have been given so far.

For example said radiation field is a laser beam.

In particular, said radiation field is a pulsed radiation field, for example a pulsed laser beam.

In another embodiment, an intensity of said radiation field is continuous in time.

Said radiation field has a wave length L.

Said wave length L of said radiation field is for example larger than <NUM>, preferably larger than <NUM>, for example larger than <NUM>, in particular larger than <NUM>.

Preferably, said wave length L of said radiation field is smaller than <NUM>, advantageously smaller than <NUM>, for example smaller than <NUM>, in particular smaller than <NUM>.

In a particular advantageous embodiment, said radiation field enters said radiation field amplifier system essentially linearly polarized with an initial polarization direction P.

An advantageous embodiment provides, that said radiation field exits said radiation field amplifier system essentially linearly polarized in said initial polarization direction P, with said radiation field being essentially linearly polarized in said initial polarization direction P in particular if a component of said radiation field, which is polarized perpendicular to said initial polarization direction P, contributes less than <NUM> %, for example less than <NUM> % advantageously less than <NUM>,<NUM> % to said radiation field.

The radiation field amplifier system comprises a first optical device and a second optical device.

Said radiation field penetrates said first optical device, said amplifying unit and said second optical device in this order.

In principle, said optical devices can be built in various ways.

Said optical devices are part of said heat dissipation system.

An advantageous embodiment provides, that the elements of said optical devices comprise a material which is for said radiation field transparent.

In particular, the elements of said optical devices comprise a material, which is in an unloaded state optical isotropic.

In particular, said unloaded state is an unpressed state and/or a stress free state and/or a state in which no external forces, for example exerted by a mounting system, are acting and/or an unheated state, for example a state at room temperature, and/or a radiation free state, in particular a state without said radiation field and/or without a pumping radiation field.

For example, said optical devices act birefringently on said radiation field and in particular said birefringence in at least one of said first and second optical devices is induced by stress and/or thermal gradients within said at least one optical device.

In particular, a depolarization of said radiation field in at least one of said optical devices is caused by thermal and/or stress induced birefringence.

A preferable embodiment provides, that at least one of said optical devices is rotational symmetric to a main axis, for example said first optical device is rotational symmetric to a first main axis and/or said second optical device is rotational symmetric to a second main axis.

In particular, said first and second main axes are essentially parallel with said axes being essentially parallel if an angle between said axes is smaller than <NUM>°, in particular smaller than <NUM>°, advantageously smaller than <NUM>,<NUM>°.

In particular a direction of penetration of said radiation field is essentially parallel to an axial direction of at least one of said main axes, for example of said first axis and/or said second axis, with said directions being essentially parallel if an angle between said directions is smaller than <NUM>°, preferably smaller than <NUM>°, for example smaller than <NUM>,<NUM>°.

Advantageously, said first optical device is and/or said second optical device is rotational symmetric to an optical axis of said radiation field amplifier system. In principle, said optical devices can comprise transitive and reflective elements.

Said radiation field penetrates all elements of at least one of said optical devices, in particular all elements of said first and said second optical devices, only in transmission.

Therefore, there is no need for highly reflective layers, which are thicker than anti-reflection layers and have accordingly a higher thermal resistance, which is undesirably.

An advantageous embodiment however provides, that said first optical device and said second optical device are build and/or arranged analogously, such that distortions to said radiation field, which occur in said optical devices, for example depolarizations of said radiation field, are similar in both of said optical devices.

In particular, said optical devices are aligned symmetrically to each other, in particular with respect to a plane of symmetry, which runs transverse to said optical axis of said radiation field amplifier system.

In particular, an optical path length through one of said optical devices depends on the polarization of the radiation field penetrating said one optical device.

In particular, optical path lengths through at least one of said optical devices are for two components of said radiation field, which are polarized perpendicular to each other, different.

For example there is a difference between an optical path length for one component of said radiation field through said first optical device and an optical path length for another component of said radiation field, which is polarized perpendicular to said aforementioned component of said radiation field, through said first optical device.

For example there is a difference between an optical path length for one component of said radiation field through said second optical device and an optical path length for another component of said radiation field, which is polarized perpendicular to said aforementioned component of said radiation field, through said second optical device.

In a preferred embodiment a difference of said optical path length of two components of said radiation field, which are polarized perpendicular to each other, is essentially the same in said first optical device and in said second optical device, with said difference in said first optical device and said difference in said second optical device being essentially the same, if said differences are the same or deviate from each other by at most <NUM> %, in particular by at most <NUM> %, preferably by at most <NUM> %.

The advantage of said essentially same differences of said optical path lengths is, that the two different components of said radiation field acquire essentially the same phase shift in both of said optical devices and therefore the compensation of the depolarizations occurring in both of said optical devices is enhanced.

In particular said two components of said radiation field, which are polarized perpendicular to each other, are exposed to different refractive indices, which differ with respect to their values, in said first optical device.

In particular said two components of said radiation field, which are polarized perpendicular to each other, are exposed to different refractive indices, which differ with respect to their values, in said second optical device.

Preferably said differences in refractive indices, to which said two components of said radiation field, which are polarized perpendicular to each other, are exposed, in said first optical device and in said second optical device are essentially the same, with said differences being essentially the same, if said differences are the same or deviate from each other by at most <NUM> %, in particular by at most <NUM> %, preferably by at most <NUM> %.

Accordingly, said depolarizations of said radiation field occurring in said first optical device and in said second optical device are essentially the same and preferably said compensation of said depolarizations is enhanced.

In particular, at least one of said optical devices, for example said first optical device and/or said second optical device, is mechanically subjected to a force.

For example said force, to which said at least one of said optical devices is subjected, is exposed by a mounting system, for example to fix a position of said at least one optical device and/or to press said at least one optical device against said amplifying unit.

An advantageous embodiment provides that said force, to which said at least one of said optical devices is subjected, is applied rotationally symmetrical to said main axis, for example to said first main axis and/or said second main axis, such that a stress induced birefringence of said at least one of said optical devices is also rotationally symmetrical to said main axis.

Preferably, said force, to which said at least one of said optical devices is subjected, is applied rotationally symmetrical to said optical axis of said radiation field amplifier system.

For example, said force, to which said first optical device is subjected, is applied rotationally symmetrical to said first main axis, preferably in axial direction with respect to said first main axis.

In particular, said force, to which said second optical device is subjected, is applied rotationally symmetrical to said second main axis and preferably in axial direction with respect to said second main axis.

An advantageous embodiment provides, that a strength of the force, to which at least one of said optical devices is subjected, for example the strength of the force to which said first optical device is subjected and/or the strength of the force to which said second optical device is subjected, is adjusted to increase, in particular to optimize, the efficiency of said radiation field amplifier system.

Factors of influence on the efficiency of said radiation field amplifier system, which are affected by said strength of the force, to which at least one of said optical devices is subjected, are for example one or more of the following: Diffraction losses in said radiation field and/or stress induced birefringence in said optical devices and/or interfacial properties between said pressed optical device and said amplifying unit.

For example, said force, to which said at least one of said optical devices is subjected, is larger than <NUM> Newton, in particular larger than <NUM> Newton, preferably larger than <NUM> Newton.

For example, said force, to which said at least one of said optical devices is subjected, is smaller than <NUM> Newton, in particular smaller than <NUM> Newton, preferably smaller than <NUM> Newton.

An advantageous embodiment provides, that the strength of the force, to which said first optical device is subjected, is essentially the same as the strength of the force, to which said second optical device is subjected with the strengths of the forces being essentially the same if they differ with respect to each other by at most <NUM> %, preferably by at most <NUM> %, in particular by at most <NUM>,<NUM> %.

Therefore, advantageously the stress induced birefringence in said first optical device and in said second optical device is essentially the same.

In principle, there are various ways to fix said optical devices and to load said optical devices.

For example at least one of said optical devices is fixed with a screw connection.

One embodiment provides, that said force, to which at least one of said optical devices is subjected, is exerted by said screw connection.

Preferably, said force, to which at least one of said optical devices is subjected, is exerted by a force exerting unit, with which a strength of said force is adjustable, in particular with which said force is adjustable during operation of said radiation field amplifier system.

Advantageously, the strength of said force, to which at least one of said optical devices is subjected, is held essentially constant at a desired strength, that is in particular that the strength of said force deviates from said desired strength by at most <NUM> %, preferably by at most <NUM> %, in particular by at most <NUM> %, advantageously by at most <NUM>,<NUM> %.

Preferably, said force, to which at least one of said optical devices is subjected, is exerted by a piezoelectric element, with which advantageously said force is easily adjustable and fine tunable.

Another advantageous embodiment provides, that at least one of said optical devices is spring loaded, for example said first optical device is spring loaded and/or said second optical device is spring loaded.

For example, a spring of said mounting system loads said at least one of said optical devices.

Thereby the exerted force is better adjustable.

Furthermore said spring compensates changes in said at least one of said optical devices and/or said mounting system, for example a thermal expansion of an element, and consequently the exerted force is more balanced.

With respect to said amplifying unit no further details have been given so far.

Preferably, said amplifying unit comprises a solid body, which in particular is disc-like shaped, that is an extension B of said solid body within a geometrical disc plane is larger, for example four times larger, than a thickness E of said solid body across said geometrical disc plane.

Advantageously, said geometrical disc plane, in which said solid body mainly extends, runs transverse to said optical axis of said radiation field amplifier system.

In particular said geometrical disc plane, in which said solid body mainly extends, runs transverse to said direction of penetration of said radiation field.

In particular said thickness E of said solid body is, in particular in the unloaded state, larger than <NUM> micrometer, in particular larger than <NUM> micrometer.

For example said thickness E of said solid body is, in particular in the unloaded state, smaller than <NUM> micrometer, preferably smaller than <NUM> micrometer, advantageously smaller than <NUM> micrometer, in particular smaller than <NUM> micrometer.

In particular, said solid body of said amplifying unit comprises a laser active material.

For example said amplifying unit comprises titan.

In particular said amplifying unit comprises aluminum oxide, Al<NUM>O<NUM>.

For example said amplifying unit comprises sapphire, in particular titanium doped sapphire.

Preferably, said amplifying unit comprises yttrium aluminium garnet, Y<NUM>Al<NUM>O<NUM>, in particular ytterbium doped and/or neodymium doped and/or thulium doped yttrium aluminum garnet.

In a pumped state pumping energy is provided to that amplifying unit.

In particular, in pumping energy excites a laser active transition in said amplifying unit, in particular in said laser active material.

Advantageously, said radiation field is amplified by said amplifying unit, in particular by stimulated emission of said excited laser active transition. Furthermore, said amplifying unit is heated by said pumping energy.

Said amplifier system comprises a source of a pumping radiation field and said pumping radiation field provides said pumping energy. Preferably, said force exerting unit is capable to compensate for a thermal expansion of said amplifying unit and in particular to held the strength of the exerted force during operation of said amplifier system essentially constant, i.e., for example within a range of ± <NUM> %, preferably of ± <NUM> %, in particular of ± <NUM> %, advantageously of ± <NUM>,<NUM> % around the desired strength of the force.

For example, said amplifying unit acts birefringently on said radiation field.

Advantageously, said amplifying unit alters, in particular rotates and/or inverts, a polarization of said radiation field such that said depolarization of said radiation field occurring in said first optical device is essentially compensated by said depolarization of said radiation field occurring in said second optical device.

Accordingly, said depolarizations occurring in said first and second optical devices are essentially compensated, such that depolarization losses in said radiation field are reduced and consequently the efficiency of said radiation field amplifier system is enhanced.

Furthermore, in that embodiment no additional parts are required to compensate depolarizations in said radiation field.

Advantageously, a direction of rotation of polarization of said radiation field is reversed by said amplifying unit, in particular when said radiation field enters said amplifying unit elliptically polarized.

A preferred embodiment provides, that said amplifying unit inverts a phase shift between components of said radiation field, which are polarized parallel and perpendicular to said initial polarization direction P of said radiation field.

In particular, said amplifying unit, in particular said solid body, is intrinsic birefringent.

For example, said amplifying unit, in particular said solid body, has a polarization dependent refractive index n, with refractive index n acquires a value n1 for a radiation field, which is polarized in a direction U1 and refractive index n acquires a value n2, which differs from value n1, for a radiation field, which is polarized in a direction U2, and directions U1 and U2 being perpendicular to each other and to said optical axis of said radiation field amplifier system and in particular being perpendicular to said direction of penetration of said radiation field.

An advantageous embodiment provides, that said amplifying unit is designed as a half wave plate.

In particular, an optical path length through said amplifying unit for a radiation field depends on a polarization of said radiation field.

Preferably, optical path lengths through said amplifying unit for components of said radiation field, which are polarized parallel and perpendicular to said initial polarization direction P of said radiation field, differ essentially by an odd multiple of the half of said wave length L of said radiation field, that is said optical path lengths differ by an amount which equals (<NUM> + <NUM>) L / <NUM> or deviates from the value (<NUM> + <NUM>) L / <NUM> by at most ± L / <NUM>, in particular by at most ± L / <NUM>, advantageously by at most ± L / <NUM> and where m is <NUM> or an integer, for example m equals <NUM> or m equals <NUM> or m equals <NUM>.

Thereby the polarization of said radiation field is altered such, that said depolarizations, which occur in said first and second optical devices, are compensated in an advantageous way.

In particular, a value of said thickness E of said solid body satisfies essentially the equation (n1 - n2) E = (<NUM> + <NUM>) x L / <NUM>, with m being an integer, for example m equals <NUM> or m equals <NUM> or m equals <NUM> or m equals <NUM>, and the value of said thickness E of said solid body satisfies essentially said equation if the value of said thickness E corresponds to the value given by said equation or differs from said value given by said equation by at most ± L /(<NUM> n1 - <NUM> n2), preferably by at most ± L /(<NUM> n1 - <NUM> n2), advantageously by at most ± L /(<NUM> n1 - <NUM> n2).

With respect to said heat dissipation system no further details have been given so far.

For example said heat dissipation system comprises one heat spreading element.

Advantageously, said heat dissipation system comprises several heat spreading elements.

In a preferred embodiment said amplifying unit is clamped in between a first and a second heat spreading element of said heat dissipation system, and thereby for example these elements are held in their positions and in particular the heat conductance between said amplifying unit and said heat spreading elements is enhanced.

Advantageously, said heat spreading elements, which are pressed against said amplifying unit, in particular said first and said second heat spreading elements, are in thermal contact with one or more heat sinks and thereby advantageously heat is further conducted away from said amplifying unit.

Preferably said one or more heat sinks comprises/comprise one or more heat spreading elements and in particular a cooling system.

Preferably at least one heat spreading element comprises, in particular all heat spreading elements comprise, a heat conducting material with a thermal conductivity of at least <NUM> W / (m x K).

In particular, at least one heat spreading element comprises, preferably all heat spreading elements comprise, diamond, which can be polycrystalline diamond and preferably is monocrystalline diamond.

Preferably, at least one heat spreading element of said heat dissipation system is an element of one of said first and second optical devices, and accordingly in turn, said one of said first and second optical devices is at least partly part of said heat dissipation system.

All heat spreading elements are elements of either said first optical device or said second optical device.

For example a first heat spreading element is an element of said first optical device and a second heat spreading element is an element of said second optical device.

Said radiation field penetrates at least one heat spreading element.

A region of penetration of said radiation field passes through the contact area within which said one heat spreading element or at least one of said several heat spreading elements is pressed against said amplifying unit. For example, said radiation field passes through a surface of a second part of said one heat spreading element or one of said several heat spreading elements, in particular through a surface of a second part of said first heat spreading element and/or a surface of a second part of said second heat spreading element.

In particular, said at least one heat spreading element comprising said contact part and said second part is one piece, i.e., said contact part and said second part are preferably integrally formed as one piece.

In one embodiment said surface of said second part of said heat spreading element is essentially planar.

In another preferred embodiment, said surface of said second part of said heat spreading element is shaped to form the shape of said radiation field.

In particular, said surface of said second part of said heat spreading element is convex.

In another embodiment said surface of said second part of said heat spreading element is concave.

Preferably said surfaces of said second parts of said first and/or second heat spreading elements are convex and/or concave.

For example, said first heat spreading element is pressed within a first contact area against said amplifying unit and said second heat spreading element is pressed within a second contact area against said amplifying unit and said region of penetration of said radiation field passes through said first contact area and said second contact area.

In a preferred embodiment said first contact area between said first heat spreading element and said amplifying unit and said second contact area between said second heat spreading element and said amplifying unit are arranged on opposite sides of said amplifying unit, such that preferably said region of penetration of said radiation field passes through said first and second contact areas and said radiation field penetrates said first and second contact areas and thereby diffraction losses in said radiation field at an interface between said heat spreading elements and said amplifying unit are reduced.

The distance d between the contact surface and the geometrical reference plane of said one heat spreading element or of at least one of said several heat spreading elements, in particular of said first heat spreading element and/or of said second heat spreading element, increases, in particular continuously, from an outer area of said heat spreading element towards the central area of said heat spreading element and said outer area surrounds said central area.

Said first heat spreading element has a first contact surface and a first geometrical reference plane is associated to said first contact surface and said first contact surface rises from said first geometrical reference plane and, in particular in the unloaded state, a distance d1 between said first contact surface and said first geometrical reference plane of said first heat spreading element increases, in particular continuously, from a first outer area towards a first central area of said first heat spreading element and in particular said first outer area surrounds said first central area and advantageously said distance d1 attains its maximal value within said first central area.

For example said second heat spreading element has a second contact surface and a second geometrical reference plane is associated to said second contact surface and said second contact surface rises from said second geometrical reference plane and, in particular in the unloaded state, a distance d2 between said second contact surface and said second geometrical reference plane of said second heat spreading element increases, in particular continuously, from a second outer area towards a second central area of said second heat spreading element and in particular said second outer area surrounds said second central area and advantageously said distance d1 attains its maximal value within said second central area.

Preferably, in particular in the unloaded state, the distance d between the contact surface and the geometrical reference plane of said one heat spreading element or of at least one of said several heat spreading elements, for example said distance d1 between said first contact surface and said first geometrical reference plane of said first heat spreading element and/or said distance d2 between said second contact surface and the second geometrical reference plane of said second heat spreading element, increases, in particular continuously, upon decreasing a radial distance to said optical axis of said radiation field amplifier system.

For example, the distance d between the contact surface and the geometrical reference plane of said one heat spreading element or of at least one of said several heat spreading elements, for example said distance d1 between said first contact surface and said first geometrical reference plane of said first heat spreading element and/or said distance d2 between said second contact surface and the second geometrical reference plane of said second heat spreading element, increases, in particular in the unloaded state, stepwise.

In particular, the distance d between the contact surface and the geometrical reference plane of said one heat spreading element or of at least one of said several heat spreading elements, for example said distance d1 between said first contact surface and said first geometrical reference plane of said first heat spreading element and/or said distance d2 between said second contact surface and the second geometrical reference plane of said second heat spreading element, increases, in particular in the unloaded state, steadily.

In particular, said optical axis of said radiation field amplifier system runs through the central area of said one heat spreading element or through every central area of each of said several heat spreading elements.

Preferably, the central area of said one heat spreading element or of at least one of said several heat spreading elements, for example said first central area of said first heat spreading element and/or said second central area of said second heat spreading element, is arranged within the region of penetration of said radiation field.

Thereby an interface between said heat spreading element and said amplifying unit at said contact surface is shaped advantageously such, that diffraction losses in said radiation field when penetrating said interface are reduced.

In a preferred embodiment, the distance d between the contact surface and the geometrical reference plane of said one heat spreading element or of at least one of said several heat spreading elements in the contact area is smaller in a pressed state, i.e., when the considered heat spreading element, said contact surface and said geometrical reference plane of which are considered, is pressed against said amplifying unit, than in an unpressed state of said considered heat spreading element.

In particular, said distance d1 between said first contact surface and said first geometrical reference plane of said first heat spreading element in said first contact area is smaller in the pressed state, i.e., when said first heat spreading element is pressed against said amplifying unit, than in an unpressed state of said first heat spreading element.

In particular, said distance d2 between said second contact surface and said second geometrical reference plane of said second heat spreading element in said second contact area is smaller in the pressed state, i.e., when said second heat spreading element is pressed against said amplifying unit, than in an unpressed state of said second heat spreading element.

Furthermore, in said pumped state said amplifying unit, in particular said solid body, expands due to thermal expansion and said amplifying unit and said one or at least one heat spreading element, in particular said first heat spreading element and/or said second heat spreading element, are pressed against each other.

Preferably, the distance d between the contact surface and the geometrical reference plane of said one heat spreading element or of at least one of said several heat spreading elements in the contact area is smaller in the pumped state than in the unpumped state.

In particular, said distance d1 between said first contact surface and said first geometrical reference plane of said first heat spreading element in said first contact area is smaller in the pumped state than in the unpumped state.

In particular, said distance d2 between said contact surface and said second geometrical reference plane of said second heat spreading element is in said second contact area smaller in the pumped state than in the unpumped state.

In some embodiments it is provided, that in the pressed state and/or pumped state, in particular in a state when it is pressed and pumped, the distance d between the contact surface and the geometrical reference plane of said one heat spreading element or of at least one of said several heat spreading elements partly increases and partly decreases upon increasing the radial distance from said optical axis of said amplifier system.

In particular, said distance d1 between said first contact surface and said first geometrical reference plane of said first heat spreading element partly increases and partly decreases upon increasing the radial distance from said optical axis of said amplifier system in the pressed state and/or pumped state, in particular in a state, when it is pressed and pumped.

In particular, said distance d2 between said second contact surface and said second geometrical reference plane of said second heat spreading element partly increases and partly decreases upon increasing the radial distance from said optical axis of said amplifier system in the pressed state and/or in the pumped state, in particular in a state, when it is pressed and pumped.

Thereby advantageously distortions between said heat spreading element and said amplifying unit at said contact surface are reduced and accordingly the heat conductance between said heat spreading element and said amplifying unit is enhanced and diffraction losses in said radiation field when penetrating through said contact surface are reduced.

In principle, the geometrical reference plane of the one heat spreading element or the geometrical reference planes of the several heat spreading elements can be aligned in various different ways.

Preferably, the geometrical reference plane of said one heat spreading element or of at least one heat spreading element of said several heat spreading elements, in particular said first geometrical reference plane and/or said second geometrical reference plane, runs essentially perpendicular to said optical axis of said radiation field amplifier system, in particular an angle between said geometrical reference plane and said optical axis differs from <NUM>° by at most ± <NUM>°, preferably by at most ± <NUM>°, in particular by at most ± <NUM>,<NUM>°, advantageously by at most ± <NUM>,<NUM>°.

For example, the geometrical reference plane of said one heat spreading element or of at least one heat spreading element of said several heat spreading elements, in particular said first geometrical reference plane and/or said second geometrical reference plane, runs essentially parallel to said geometrical disc plane of said solid body, within which said solid body essentially extends, in particular an angle between said geometrical reference plane and said geometrical disc plane is smaller than <NUM>°, in particular smaller than <NUM>°, advantageously smaller than <NUM>,<NUM>°.

There are various ways in which the contact surface of said one heat spreading element or of at least one heat spreading element of said several heat spreading elements can rise over the geometrical reference plane of said heat spreading element.

For example the contact surface of said one heat spreading element or of at least one heat spreading element of said several heat spreading elements is stepped.

Advantageously, the contact surface of said one heat spreading element or of at least one heat spreading element of said several heat spreading elements, in particular said first contact surface and/or said second contact surface, is curved, in particular convex curved, with a radius Q of curvature of said contact surface being, in particular in the unloaded state, larger than <NUM>,<NUM> meter, preferably larger than <NUM> meter, in particular larger than <NUM> meter.

Advantageously, the contact surface of said one heat spreading element or of at least one heat spreading element of said several heat spreading elements, for example said first contact surface and/or said second contact surface, is curved, in particular convex curved, with the radius Q of curvature of said contact surface being, in particular in the unloaded state, smaller than <NUM> meter, advantageously smaller than <NUM> meter, preferably smaller than <NUM> meter.

In a preferred embodiment the radii Q of curvature of the contact surfaces of at least two heat spreading elements, for example of said first and said second contact surfaces, in particular of the contact surfaces of all heat spreading elements, differ with respect to each other, in particular in the unloaded state, by at most <NUM> %, in particular by at most <NUM> %, preferably by at most <NUM> %.

An advantageous embodiment provides, that an extension C, which is measured transverse to said optical axis of said radiation field amplifier system, of said one heat spreading element or of at least one heat spreading element of said several heat spreading elements, in particular of said first heat spreading element and/or of said second heat spreading element, is, in particular in the unloaded state, larger than <NUM>, preferably larger than <NUM>, in particular larger than <NUM>.

In particular, the extension C which is measured transverse to said optical axis of said radiation field amplifier system of said one heat spreading element or of at least one heat spreading element of said several heat spreading elements, in particular of said first heat spreading element and/or said second heat spreading element, is, in particular in the unloaded state, smaller than <NUM>, preferably smaller than <NUM>, advantageously smaller than <NUM>.

For example a ratio C / Q of the extension C, which is measured transverse to said optical axis of said radiation field amplifier system, of said one heat spreading element or of at least one heat spreading element of said several heat spreading elements, in particular of said first heat spreading element and/or of said second heat spreading element, to the radius Q of curvature of the contact surface of said heat spreading element is, in particular in the unloaded state, larger than <NUM>,<NUM>, advantageously larger than <NUM>,<NUM>, in particular larger than <NUM>,<NUM>.

Advantageously the ratio C / Q of the extension C, which is measured transverse to said optical axis of said radiation field amplifier system, of said one heat spreading element or of at least one heat spreading element of said several heat spreading elements, in particular of said first heat spreading element and/or of said second heat spreading element, to the radius Q of curvature of the contact surface of said heat spreading element is, in particular in the unloaded state, smaller than <NUM>,<NUM>, advantageously smaller than <NUM>,<NUM>, preferably smaller than <NUM>,<NUM>, in particular smaller than <NUM>,<NUM>.

Preferably the extensions C, which are measured transverse to said optical axis of said radiation field amplifier system, of at least two heat spreading elements, for example of said first and said second heat spreading elements, preferably of all heat spreading elements, differ with respect to each other, in particular in the unloaded state, by at most <NUM> %, preferably by at most <NUM> %, in particular by at most <NUM> %.

In a preferred embodiment a thickness T of said one heat spreading element or of at least one heat spreading element of said several heat spreading elements, in particular of said first heat spreading element and/or of said second heat spreading element, with the thickness T being measured in axial direction with respect to said optical axis of said radiation field amplifier system, is, in particular in the unloaded state, larger than <NUM>,<NUM>, preferably larger than <NUM>,<NUM>, in particular larger than <NUM>.

For example the thickness T of said one heat spreading element or of at least one heat spreading element of said several heat spreading elements, in particular of said first heat spreading element and/or of said second heat spreading element, with the thickness T being measured in axial direction with respect to said optical axis of said radiation field amplifier system, is, in particular in the unloaded state, smaller than <NUM>, preferably smaller than <NUM>, in particular smaller than <NUM>.

Advantageously, the thicknesses T of at least two heat spreading elements, for example of said first and said second heat spreading elements, in particular of all heat spreading elements, differ with respect to each other, in particular in the unloaded state, by at most <NUM> %, preferably by at most <NUM> %, in particular by at most <NUM> %.

In a preferred embodiment a ratio Q / T of the radius Q of curvature of the contact surface of said one heat spreading element or of at least one heat spreading element of said several heat spreading elements, in particular of said first contact surface and/or of said second contact surface, to the thickness T, which is measured in axial direction with respect to said optical axis of said radiation field amplifier system, of said heat spreading element is, in particular in the unloaded state, larger than <NUM>, advantageously larger than <NUM>, in particular larger than <NUM>, preferably larger than <NUM>.

In a preferred embodiment the ratio Q / T of the radius Q of curvature of the contact surface of said one heat spreading element or of at least one heat spreading element of said several heat spreading elements, in particular of said first contact surface and/or of said second contact surface, to the thickness T, which is measured in axial direction with respect to said optical axis of said radiation field amplifier system, of said heat spreading element is, in particular in the unloaded state, smaller than <NUM>, advantageously smaller than <NUM>, in particular smaller than <NUM>, preferably smaller than <NUM>.

Preferably, a ratio C / T of the extension C, which is measured transverse to said optical axis of said radiation field amplifier system, of said one heat spreading element or of at least one heat spreading element of said several heat spreading elements, in particular of said first heat spreading element and/or of said second heat spreading element, to the thickness T, which is measured in axial direction with respect to said optical axis of said radiation field amplifier system, of said heat spreading element is, in particular in the unloaded state, larger than <NUM>, in particular larger than <NUM>, preferably larger than <NUM>.

Preferably, the ratio C / T of the extension C, which is measured transverse to said optical axis of said radiation field amplifier system, of said one heat spreading element or of at least one heat spreading element of said several heat spreading elements, in particular of said first heat spreading element and/or of said second heat spreading element, to the thickness T, which is measured in axial direction with respect to said optical axis of said radiation field amplifier system, of said heat spreading element is, in particular in the unloaded state, smaller than <NUM>, in particular smaller than <NUM>, preferably smaller than <NUM>.

There are various ways to exert the force on said one heat spreading element or on at least one of said several heat spreading elements.

Preferably said mounting system exerts the force on at least one heat spreading element, in particular to all heat spreading elements.

Preferably, said force, which is exerted on said heat spreading element, is exerted by a force exerting unit, with which advantageously a strengths of said force is adjustable, in particular adjustable during operation of said radiation field amplifier system and/or with which an essentially constant force is exertable, in particular during operation of said radiation field amplifier system, where the force is essentially constant in particular when it varies around a constant value by at most <NUM> %, preferably by at most <NUM> %, in particular by at most <NUM> %, for example by at most <NUM> %.

For example, the force exerting unit comprises at least one piezoelectric element.

Advantageously, with said at least one piezo electric element the force is adaptable during operation of said amplifier system and in particular can be adjusted to compensate for thermal expansions of said amplifying unit.

Advantageously, the force exerting unit comprises at least one spring.

An advantageous embodiment provides, that at least one heat spreading element is spring actuated, for example said first heat spreading element and/or said second heat spreading element is/are spring actuated, in particular all heat spreading elements are spring actuated.

Advantageously, all heat spreading elements are actuated by a same at least one spring, such that the strengths of the forces to which said heat spreading elements are exposed to, are essentially the same.

Advantageously, the spring, which actuates said at least one spring actuated heat spreading element, levels off changes in said heat dissipation system and/or said mounting system, such that the force, to which said at least one heat spreading element is exposed, is balanced.

A preferred embodiment provides, that a strength of a force with which said one heat spreading element or at least one of said several heat spreading elements, for example said first heat spreading element and/or said second heat spreading element, is pressed against said amplifying unit is adjustable by said mounting system and in particular is adjustable before and/or during and/or after operation of said radiation field amplifier system.

Preferably, the strength of the force with which said at least one pressed heat spreading element is pressed against said amplifying unit is adjusted to increase, in particular optimize, the efficiency of said radiation field amplifier system.

In particular, factors of influence of the strength of the force on the efficiency of said amplifier system comprise one or more of the following factors:
Increasing the strength of the pressing force may result in an improved interface between said amplifying unit and said at least one heat spreading element leading to an increased heat conductance between these elements, whereas at too large strengths of the pressing force said at least one heat spreading element may detach within the region of penetration from said amplifying unit resulting in a decrease of the heat conductance and an increase of diffraction losses within said radiation field.

Moreover, the strength of the pressing force is furthermore in particular limited to reasonable values of the strength, not to damage elements of said amplifier system, for example said heat spreading elements and/or said amplifying unit and/or elements of said optical devices.

Advantageously, the strength of the force with which said at least one pressed heat spreading element is pressed against said amplifying unit is adjusted to reduce distortions within said radiation field, in particular to reduce distortions within said radiation field which occur in said at least one pressed heat spreading element and/or said amplifying unit and/or in the contact area between said at least one pressed heat spreading element and said amplifying unit.

Thereby an easy way to improve the efficiency of said radiation field amplifier system is provided.

In particular for a certain strength of the force with which at least one pressed heat spreading element is pressed against said amplifying unit, the distortions within said radiation field are minimized and the force with which said at least one pressed heat spreading element is pressed against said amplifying unit is adjusted such that its strength is larger than said certain strength of the force and/or is essentially the same as said certain strength of the force at which said distortions within said radiation field are minimal, with said strengths being essentially the same if they differ with respect to each other by less than <NUM> %, advantageously by less than <NUM> %, preferably by less than <NUM> %, for example by less than <NUM> %.

In a preferred embodiment said radiation field amplifier system comprises an adjustment unit.

In particular said adjustment unit enables an adjustment of said one heat spreading element or of at least one of said several heat spreading elements, for example of said first heat spreading element and/or of said second second heat spreading element, in particular an adjustment of all heat spreading elements.

An advantageous embodiment provides, that said adjustment unit for adjusting said at least one adjustable heat spreading element is there to adjust said one or at least one adjustable heat spreading element such that the central area of said one or at least one adjustable heat spreading element lies within the contact area of said one or at least one adjustable heat spreading element.

Preferably said adjustment unit for adjusting said one or at least one adjustable heat spreading element is there to adjust said one or at least one adjustable heat spreading element into a desired position.

In particular, in said desired position said region of penetration of said radiation field passes through the contact area between said one or at least one adjustable heat spreading element and said amplifying unit, in particular through the central area of said one or at least one adjustable heat spreading element.

Preferably, with said adjustment unit at least two heat spreading elements, in particular said first and said second heat spreading elements, are adjustable into desired positions.

For example, in said desired positions the contact areas of said at least two adjustable heat spreading elements are aligned with respect to each other, in particular such that said region of penetration of said radiation field passes through said two contact areas.

Advantageously, in said desired position/in said desired positions said pumping radiation field passes through the contact areas between said adjustable heat spreading elements and said amplifying unit, in particular through the central areas of said adjustable heat spreading elements.

Advantageously, said adjustment unit enables an adjustment of at least one optical element of at least one of said optical devices.

In particular said adjustment unit enables an adjustment of said first optical element of said first optical device and/or of said second optical element of said second optical device.

Further features and explanations with respect to the present invention are disclosed in connection with the detailed specification and the drawings.

A radiation field generating unit <NUM> comprises a radiation field source <NUM>, which generates an initial radiation field <NUM> and initial radiation field <NUM> enters as a penetrating radiation field <NUM> a radiation field amplifier system <NUM>, as it is sketched exemplarily in <FIG>.

Penetrating radiation field <NUM> propagates essentially in an axial direction with respect to an optical axis <NUM> of radiation field amplifier system <NUM>.

For example, there is a first polarization selecting element <NUM>, for example a polarization filter and first polarization selecting element <NUM> is arranged in between source <NUM> and amplifier system <NUM>.

Initial radiation field <NUM> propagates from source <NUM> towards first polarization selecting element <NUM>, which converts initial radiation field <NUM> into radiation field <NUM>, and radiation field <NUM> propagates towards amplifier system <NUM> and passes through amplifier system <NUM>.

Preferably, there is a second polarization selecting element <NUM>, for example a polarization filter, which in relation to the axial direction of optical axis <NUM> follows amplifier system <NUM>.

Accordingly, penetrating radiation field <NUM> propagates from amplifier system <NUM> towards second polarization selecting element <NUM> and second polarization selecting element <NUM> converts penetrating radiation field <NUM> into a provided radiation field <NUM>.

Initial radiation field <NUM> and thus penetrating radiation field <NUM> and provided radiation field <NUM> have a wave length L and in particular radiation fields <NUM>, <NUM> and <NUM> are laser beams.

Initial radiation field <NUM> is in particular essentially linearly polarized with a polarization direction P1.

Polarization selecting element <NUM> removes components of initial radiation field <NUM>, which are polarized transverse to a selecting polarization direction S1, and provides radiation field <NUM> linearly polarized with a polarization direction parallel to direction S1.

For example polarization selecting element <NUM> is provided to remove depolarizations in initial radiation field <NUM> and to do so polarization direction P1 and selecting polarization direction S1 of polarization selecting element <NUM> are parallel to each other.

In a variation of the present embodiment, polarization direction P1 and selecting polarization direction S1 are at an angle to each other and in consequence only that component of initial radiation field <NUM>, which is polarized in direction of selecting polarization direction S1, passes through first polarization selecting element <NUM> and converts to radiation field <NUM>.

Accordingly, an intensity of radiation field <NUM> is reduced with respect to an intensity of initial radiation field <NUM> with the amount of reduction depending on the angle between the directions P1 and S1, where the intensity of radiation field <NUM> is vanishingly small for the angle being <NUM>° and the intensity of radiation field <NUM> being essentially the intensity of initial radiation field <NUM> for the angle being essentially zero.

The intensity of radiation field <NUM> is continuously adjustable between these two extreme values by adjusting the angle between the polarization direction P1 of radiation field <NUM> and selecting polarization direction S1 of polarization selecting element <NUM> accordingly.

Therefore, radiation field <NUM> is essentially linearly polarized in a polarization direction P with polarization direction P being parallel to selecting polarization direction S1 for embodiments comprising first polarization selecting element <NUM> and with polarization direction P being parallel to polarization direction P1 of initial radiation field <NUM> for embodiments without first polarization selecting element <NUM>.

Second polarization selecting element <NUM> removes components of radiation field <NUM>, which are polarized transverse to d selecting polarization direction S2, and in consequence provided radiation field <NUM> is essentially linearly polarized in a polarization direction P2 with direction P2 being parallel to direction S2.

In particular selecting polarization direction S2 is parallel to polarization direction P of radiation field <NUM>, for example to polarization direction P of radiation field <NUM> when entering amplifier system <NUM> or to the direction of polarization of a component contributing most to radiation field <NUM> when exiting amplifier system <NUM>, such that polarization selecting element <NUM> removes undesirable components of radiation field <NUM>, such as disturbances of the polarization of radiation field <NUM>, and provides radiation field <NUM> essentially linearly polarized.

Radiation field amplifier system <NUM> comprises a first optical device <NUM>, a second optical device <NUM> and an amplifying unit <NUM>.

Penetrating radiation field <NUM> penetrates amplifier system <NUM> in a direction <NUM> of penetration, such that penetrating radiation field <NUM> enters amplifier system <NUM> on a first side <NUM>, penetrates first optical device <NUM>, then amplifying unit <NUM> and finally second optical device <NUM> and exits amplifier system <NUM> on a second side <NUM>.

Accordingly, in relation to the propagation of penetrating radiation field <NUM> amplifying unit <NUM> is arranged between first optical device <NUM> and second optical device <NUM>.

In a variation of the embodiment, radiation field <NUM> comprises several branches with each branch of radiation field <NUM> extending from one of first or second optical device <NUM>, <NUM> to the other optical device <NUM>, <NUM> and by propagating from one optical device <NUM>, <NUM> to the other optical device <NUM>, <NUM> each branch of radiation field <NUM> passes through amplifying unit <NUM>.

Direction <NUM> of penetration is defined locally by a propagation of radiation field <NUM> in a corresponding area and the direction <NUM> of penetration of radiation field <NUM> may be changed by reflecting or refracting elements of optical devices <NUM> and <NUM> or of amplifying unit <NUM>.

Further radiation field amplifier system <NUM> comprises a pumping device <NUM>, which provides pumping energy which is needed to amplify radiation field <NUM>, and a heat dissipation system <NUM>, which enables dissipation of heat in amplifier system <NUM> and which in particular guides a flow of heat away from amplifying unit <NUM> and prevents overheating of amplifying unit <NUM>.

A mounting system <NUM> holds the elements of amplifier system <NUM> together.

Mounting system <NUM> comprises a housing <NUM> with an interior <NUM>, which contains amplifying unit <NUM> and, at least partially, optical devices <NUM> and <NUM> and heat dissipation system <NUM> (<FIG>).

Housing <NUM> extends in axial direction of a housing axis <NUM> from a first side <NUM> to a second side <NUM> and in particular housing <NUM> is essentially rotationally symmetrical with respect to housing axis <NUM>.

At first side <NUM> there is a first bounding element <NUM> and at second side <NUM> there is a second bounding element <NUM> with interior <NUM> being in between first and second bounding elements <NUM> and <NUM>.

A housing wall <NUM> extends from first bounding element <NUM> to second bounding element <NUM> with interior <NUM> being enclosed by housing wall <NUM> in radial direction to housing axis <NUM>.

For example first bounding element <NUM> is designed as a lid element which is detachable attached to housing wall <NUM>, for example with a screw connection.

At first side <NUM> there is an inlet <NUM>, for example an opening in first bounding element <NUM>, for radiation field <NUM> and at second side <NUM> there is an outlet <NUM>, for example an opening in second bounding element <NUM>, for radiation field <NUM>.

Radiation field <NUM> penetrates amplifier system <NUM> within a region <NUM> of penetration, where radiation field <NUM> enters housing <NUM> at inlet <NUM> and exits housing <NUM> at outlet <NUM>, such that region <NUM> of penetration extends within housing <NUM> between inlet <NUM> and outlet <NUM>.

Region <NUM> of penetration extends along direction <NUM> of penetration from inlet <NUM> to outlet <NUM> and is elongated in direction <NUM> of penetration and exhibits an extension transverse to direction <NUM> of penetration with a maximal extension <NUM>.

Region <NUM> of penetration is tube-like shaped with respect to optical axis <NUM>, that is region <NUM> of penetration extends in axial direction of optical axis <NUM> and maximal extension <NUM> is measured in radial direction of optical axis <NUM>.

In embodiment according to <FIG> region <NUM> of penetration is in housing <NUM> aligned along housing axis <NUM> and maximal extension <NUM> is measured in radial direction to housing axis <NUM>.

Further, mounting system <NUM> comprises a spring <NUM>, which is fixed, for example indirectly, between a first stop element <NUM> and a second stop element <NUM> and with that mounting system <NUM> provides a connection <NUM> actuated by force with spring <NUM> tightening elements of mounting system <NUM> and enabling an adjustment of an exerted force.

In particular there is a force transmitting element <NUM> between spring <NUM> and first stop element <NUM>, such that stop element <NUM> supports spring <NUM> indirectly.

In a variation of the embodiment spring <NUM> is aligned directly at first stop element <NUM>, such that first stop element <NUM> supports spring <NUM> directly.

First stop element <NUM> is for example fixed at housing <NUM>, in particular first bounding element <NUM> provides first stop element <NUM>.

Second stop element <NUM> supports spring <NUM> indirectly via connection <NUM> actuated by force with amplifying unit <NUM> and elements of optical devices <NUM> and <NUM> providing connection <NUM>, such that amplifying unit <NUM> and elements of optical devices <NUM> and <NUM> are clamped between stop element <NUM> and spring <NUM>.

For example stop element <NUM> is fixed with housing <NUM>, in particular bounding element <NUM> provides stop element <NUM>.

Spring <NUM>, for example designed as a disc spring, comprises a base element <NUM> and a limb element <NUM> with base element <NUM> providing an opening through which region <NUM> of penetration extends and in consequence radiation field <NUM> is free of interaction with spring <NUM>.

Base element <NUM> extends for example disc like essentially in a geometrical plane.

Limb element <NUM> extends from a first end <NUM> to a second end <NUM> with first end <NUM> being mounted at base element <NUM>.

A position of second end <NUM> relative to first end <NUM> is changeable with second end <NUM> possessing a relax position and several tension positions.

With second end <NUM> being in its relax position, spring <NUM> is essentially tension free, where second end <NUM> in its relaxed position being for example at a distance to the plane of base element <NUM>.

For second end <NUM> being in one of its tension positions, spring <NUM> is subjected to stress and exerts a force to adjacent elements and thereby provides force to connection <NUM>.

In particular, the distance of second end <NUM> to the plane of base element <NUM> is in the tension positions altered relative to the distance of second end <NUM> to the plane of base element <NUM> in its relaxed position, for example the distance in the tension position is reduced relative to the distance in the relax position.

Mounting system <NUM> possesses a fix state and an adjustment state with elements of mounting system <NUM> being fixed in the fix state and the adjustment state is for adjusting the force transmitted by connection <NUM>, in particular the positions of elements of mounting system <NUM> are adjustable in the adjustment state.

In the fix state, stop elements <NUM> and <NUM> are fixed relative to each other, such that a relative position of these elements is essentially constant, and spring <NUM> and other elements of mounting system <NUM> are clamped between the stop elements <NUM> and <NUM>, whereas in the adjustment state a relative position between the stop elements <NUM> and <NUM> is adjustable, such that the tension state of spring <NUM> is changeable as well as its exerted force and accordingly in the adjustment state the strength of the force transmitted by connection <NUM> is adjustable.

In embodiment according to <FIG> stop elements <NUM> and <NUM> are connected by a screwed joint <NUM> of a connection device <NUM> with screwed joint <NUM> being fixed in the fix state and offers the ability to adjust the relative distance between the stop elements <NUM> and <NUM> and in consequence the force transmitted by connection <NUM> within the adjustment state.

In particular, connection device <NUM> comprises housing wall <NUM>.

Optical device <NUM> comprises an optical element <NUM> and optical device <NUM> comprises an optical element <NUM>, which are shown enlarged in <FIG>.

Optical elements <NUM> and <NUM> are, at least partially, mounted in region <NUM> of penetration and in particular optical elements <NUM> and <NUM> are aligned symmetrical to each other with respect to a plane <NUM> of symmetry with symmetry plane <NUM> being angled, in particular perpendicular, to optical axis <NUM> and for example symmetry plane <NUM> extends in radial direction to housing axis <NUM>.

Optical elements <NUM> and <NUM> comprise a material transparent for radiation field <NUM> and in particular this material is in a stress-free and thermal gradient free state optical isotropic.

Optical element <NUM>, exemplarily shown in <FIG>, is disc-like formed, that is, optical element <NUM> extends mainly in a geometrical disc plane <NUM>, which is aligned transverse, in particular perpendicular, to a main axis <NUM>.

An extension A1 of optical element <NUM> within geometrical disc plane <NUM> is larger, in particular at least about a factor <NUM> larger, than a thickness D1 of optical element <NUM> across geometrical disc plane <NUM>, where thickness D1 is measured in particular perpendicular to disc plane <NUM> and in axial direction of main axis <NUM>.

In particular main axis <NUM> coincides with optical axis <NUM> or both axes <NUM> and <NUM> are essentially parallel, that is an angle between these axes <NUM> and <NUM> is smaller than <NUM>°, in particular smaller than <NUM>°, preferably smaller than <NUM>°.

For example, geometrical disc plane <NUM> is essentially parallel to symmetry plane <NUM>, that is an angle between planes <NUM> and <NUM> is smaller than <NUM>°, in particular smaller than <NUM>°, preferably smaller than <NUM>°.

Preferably, optical element <NUM> is rotationally symmetrical to main axis <NUM>.

Radiation field <NUM> penetrates optical element <NUM> in direction <NUM> of penetration from a first part <NUM> to a second side <NUM>, in particular across geometrical disc plane <NUM>.

Parts <NUM> and <NUM> are arranged on opposite sides of optical element <NUM> and geometrical disc plane <NUM> is aligned in between parts <NUM> and <NUM>.

Preferably, optical element <NUM> has at parts <NUM> and <NUM> anti-reflection-layers, which suppress reflection of radiation field <NUM>, when it enters or exits optical element <NUM>.

First part <NUM> is planar, that is an outer surface <NUM> of optical element <NUM> at first part <NUM> is aligned essentially in a geometrical plain plane <NUM> with geometrical plain plane <NUM> being essentially perpendicular to direction <NUM> of penetration, such that an angle between outer surface <NUM> and direction <NUM> of penetration, in particular in region <NUM> of penetration, is about <NUM>° with a deviation of at most ± <NUM>°, preferably of at most ± <NUM>°, advantageously of at most ± <NUM>° and for example geometrical plain plane <NUM> is essentially parallel to disc plane <NUM>, that is an angle between planes <NUM> and <NUM> is smaller than <NUM>°, in particular smaller than <NUM>°, preferably smaller than <NUM>°.

Second side <NUM> rises from a geometrical basis plane <NUM> in a direction <NUM> of rising with geometrical basis plane <NUM> being essentially parallel to geometrical plain plane <NUM>, and accordingly to geometrical disc plane <NUM>, such that an angle between planes <NUM> and <NUM> is in particular smaller than <NUM>°, in particular smaller than <NUM>°, preferably smaller than <NUM>° and preferably direction <NUM> of rising is directed towards direction <NUM> of penetration and thus essentially parallel to the axial direction of main axis <NUM>, with an angle between these directions being for example smaller than <NUM>°, in particular smaller than <NUM>°, preferably smaller than <NUM>°.

Second side <NUM> rises, in particular continuously increasing, from an outer area <NUM> towards a central area <NUM> with second side <NUM> being thinnest in outer are <NUM> and being thickest in central area <NUM>.

In particular outer area <NUM> surrounds central area <NUM> with outer area <NUM> being at a distance to central area <NUM>, such that for example an intermediate area is located between outer area <NUM> and central area <NUM>.

In one embodiment, main axis <NUM> passes through central area <NUM> and outer area <NUM> encloses main axis <NUM> at a radial distance.

Accordingly, an outer surface <NUM> of optical element <NUM> at second side <NUM> ascends from geometrical basis plane <NUM> at outer area <NUM> towards central area <NUM> and thereby a distance of surface <NUM> to geometrical plain plane <NUM>, in particular to outer surface <NUM>, at second side <NUM> enlarges.

For example outer surface <NUM> is convex shaped with a radius R1 of curvature being considerably larger, for example at least <NUM> times larger than thickness D1 of optical element <NUM>.

Accordingly, there is a variation of thickness D1 of optical element <NUM>, with the thickness D1 corresponds essentially to the distance between the outer surfaces <NUM> and <NUM>, along the extensions of outer surfaces <NUM> and <NUM>, but this variation is rather small, in particular due to the large radius R1 of curvature, such that the variation of thickness D1 is smaller than <NUM> %, preferably smaller than <NUM>,<NUM> % of a mean value of thickness D1.

Optical element <NUM>, exemplarily shown in <FIG>, is disc-like formed, that is optical element <NUM> extends mainly in a geometrical disc plane <NUM>, which extends essentially perpendicular to a main axis <NUM>.

An extension A2 of optical element <NUM> within geometrical disc plane <NUM> is considerably larger, for example at least a factor <NUM> larger, than a thickness D2 of optical element <NUM> across geometrical disc plane <NUM>, where thickness D2 is measured in particular perpendicular to geometrical disc plane <NUM> and in axial direction of main axis <NUM>.

Accordingly, an extension of optical element <NUM> in axial direction of main axis <NUM> is significantly smaller than an extension of optical element <NUM> in radial direction of main axis <NUM>.

In particular optical element <NUM> is rotational symmetric to main axis <NUM>, such that the extension A2 within geometrical disc plane <NUM> corresponds to a diameter of optical element <NUM>.

In particular, main axis <NUM> coincides with optical axis <NUM> or both axes <NUM> and <NUM> are essentially parallel, that is an angle between these axes <NUM> and <NUM> is smaller than <NUM>°, in particular smaller than <NUM>°, preferably smaller than <NUM>°.

In particular, geometrical disc plane <NUM> is essentially parallel to symmetry plane <NUM> and to geometrical disc plane <NUM> that is an angle between two of these planes is smaller than <NUM>°, in particular smaller than <NUM>°, preferably smaller than <NUM>°.

Radiation field <NUM> penetrates optical element <NUM> in direction <NUM> of penetration from a first part <NUM> to a second part <NUM> in particular across geometrical disc plane <NUM> with direction <NUM> of penetration being essentially parallel to the axial direction of main axis <NUM>, such that for example an angle between these directions is smaller than <NUM>°, in particular smaller than <NUM>°, preferably smaller than <NUM>°.

Parts <NUM> and <NUM> are arranged on opposite sides of optical element <NUM> and geometrical disc plane <NUM> is aligned between these parts <NUM> and <NUM>.

Preferably, optical element <NUM> has at first part <NUM> and at second part <NUM> anti-reflection-layers, which suppress reflection of radiation field <NUM> when it enters or exits optical element <NUM>.

First part <NUM> of optical element <NUM> rises from a geometrical basis plane <NUM> in a direction <NUM> of rising, which points away from second part <NUM>.

Geometrical basis plane <NUM> is for example essentially parallel to geometrical disc plane <NUM>, such that an angle between planes <NUM> and <NUM> is smaller than <NUM>°, in particular smaller than <NUM>°, preferably smaller than <NUM>°.

Direction <NUM> of rising is for example essentially parallel to the axial direction of main axis <NUM> and the axial direction of optical axis <NUM>, such that an angle between these directions is in particular smaller than <NUM>°, in particular smaller than <NUM>°, preferably smaller than <NUM>°.

First part <NUM> rises, in particular continuously increasing, from an outer area <NUM>, where second part <NUM> is thinnest, towards a central area <NUM>, where second part <NUM> is thickest, with a thickness of second part <NUM> being in particular measured from geometrical basis plane <NUM> in direction <NUM> of rising.

Outer area <NUM> surrounds for example central area <NUM> and is being at a distance to central area <NUM>, such that for example an intermediate area is located between outer area <NUM> and central area <NUM> and in one embodiment main axis <NUM> passes through central area <NUM> and outer area <NUM> encloses main axis <NUM> at a radial distance to main axis <NUM>.

Thus an outer surface <NUM> of optical element <NUM> at first part <NUM> ascends from geometrical base plane <NUM>.

Outer surface <NUM> is located in outer area <NUM> essentially in geometrical basis plane <NUM> and in central area <NUM> outer surface <NUM> is at a distance to geometrical basis plane <NUM>.

In particular outer surface <NUM> ascends from geometrical basis plane <NUM> continuously and preferably outer surface <NUM> is convex-shaped with a radius R2 of curvature being significantly larger than thickness D2 of optical element <NUM> and extension A2 of optical element <NUM>, for example radius R2 is at least <NUM> times larger than thickness D2.

Second part <NUM> of optical element <NUM> is essentially planar, that is an outer surface <NUM> of optical element <NUM> at second part <NUM> extends essentially in a geometrical plain plane <NUM>.

Geometrical plain plane <NUM> is essentially perpendicular to direction <NUM> of penetration, that is direction <NUM> of penetration is for example angled to geometrical plain plane <NUM> with an angle larger than <NUM>° and smaller than <NUM>° and in particular geometrical plain plane <NUM> is essentially parallel to geometrical disc plane <NUM>, that is an angle between these planes <NUM> and <NUM> is for example smaller than <NUM>°, in particular smaller than <NUM>°, preferably smaller than <NUM>°.

Thus, thickness D2 of optical element <NUM>, which essentially corresponds to a distance between outer surface <NUM> and outer surface <NUM> at first and second parts <NUM> and <NUM>, varies along an extension of outer surfaces <NUM> and <NUM> due to the rising of outer surface <NUM>, but the variation of thickness D2 is rather small, in particular because radius R2 of curvature is significantly larger than thickness D2, such that a variation of thickness D2 is smaller than <NUM> %, for example smaller than <NUM>,<NUM> % with respect to a mean value of thickness D2.

Advantageously, the mean value of thickness D2 is essentially the same as the mean value of thickness D1, with these values are essentially the same, if they differ with respect to each other by at most <NUM> % preferably by at most <NUM> %.

Amplifying unit <NUM> comprises a solid body <NUM> which contains a laser active material.

Solid body <NUM> is disc-like shaped within a geometrical disc plane <NUM>, such that an extension B of solid body <NUM> within geometrical disc plane <NUM> is larger, for example at least four times larger, than an extension E of solid body <NUM> across geometrical disc plane <NUM>.

For example, geometrical disc plane <NUM> corresponds to symmetry plane <NUM>.

Radiation field <NUM> penetrates solid body <NUM> in direction <NUM> of penetration from a first side <NUM> to a second side <NUM>, where direction <NUM> of penetration is in particular essentially perpendicular to geometrical disc plane <NUM>, such that an angle between direction <NUM> of penetration and geometrical disc plane <NUM> is for example larger than <NUM>° and smaller than <NUM>°.

Sides <NUM> and <NUM> are opposing sides and geometrical disc plane <NUM> is aligned between sides <NUM> and <NUM>.

Preferably solid body <NUM> has at first side <NUM> and at second side <NUM> anti-reflection layers, which suppress reflection of radiation field <NUM> when it enters or exits solid body <NUM>.

Sides <NUM> and <NUM> are planar, such that a surface <NUM> of solid body <NUM> at first side <NUM> extends essentially in a geometrical plane and a surface <NUM> of solid body <NUM> at second side <NUM> essentially extends in another geometrical plane, with this geometrical planes being essentially parallel to each other and in particular parallel to geometrical disc plane <NUM>, for example angles between two of these planes are smaller than <NUM>°, in particular smaller than <NUM>°, preferably smaller than <NUM>°.

Surfaces <NUM> and <NUM> are, in particular in region <NUM> of penetration, at a distance to each other which corresponds to thickness E of solid body <NUM> and in particular surfaces <NUM> and <NUM> are equidistant to geometrical disc plane <NUM>.

Further, solid body <NUM> comprises a birefringent medium and a refractive index n of solid body <NUM> depends on a polarization of a radiation field which penetrates solid body <NUM>.

For components of the radiation field which penetrates solid body <NUM> and which are polarized in a polarization direction U1, solid body <NUM> exposes a refractive index n1 and for components which are polarized in a direction U2 solid body <NUM> exposes a refractive index n2.

For example refractive index n2 is smaller than refractive index n1.

Directions U1 and U2 are perpendicular to each other and preferably perpendicular to optical axis <NUM> and in particular parallel to geometrical disc plane <NUM>.

Solid body <NUM> is aligned such that directions U1 and U2 are perpendicular to direction <NUM> of penetration and in particular one of directions U1 and U2 are aligned essentially parallel to initial polarization direction P of radiation field <NUM>, for example U1 being essentially parallel to initial polarization direction P, with an angle between these directions being for example smaller than <NUM>°, in particular smaller than <NUM>°, preferably smaller than <NUM>°.

In a variant of that embodiment direction U2 is essentially parallel to initial polarization direction P, such that for example an angle between these directions is smaller than <NUM>°, in particular smaller than <NUM>°, preferably smaller than <NUM>°.

Solid body <NUM> is designed as a half wave plate for radiation fields with wave length L, such that optical path lengths for components of the radiation field with wave length L, which are polarized in direction U1 and U2, respectively, differ by an odd multiple of half of the wave length L, that is the equation (n1-n2)E = (<NUM>+<NUM>) x L/<NUM> is essentially satisfied, with m being an integer, for example m=<NUM>, and in a variant of the embodiment m=<NUM>, and this equation is essentially satisfied, if the thickness E of solid body <NUM> corresponds to the value given by that equation or differs from this value by at most ± L/(<NUM> n1-<NUM> n2).

With respect to direction <NUM> of penetration solid body <NUM> is aligned in between optical elements <NUM> and <NUM>.

Optical elements <NUM> and <NUM> are aligned symmetrically with respect to symmetry plane <NUM>, and in particular the main axes <NUM> and <NUM> of optical elements <NUM> and <NUM> essentially coincide.

In the embodiment according to <FIG>, second side <NUM> of optical element <NUM>, in particular with its central area <NUM>, lies against first side <NUM> of solid body <NUM> and first part <NUM> of optical element <NUM>, in particular with its central area <NUM>, lies against second side <NUM> of solid body <NUM>.

For example geometrical disc planes <NUM>, <NUM> and <NUM> are aligned essentially parallel to each other, such that each angle between two of these planes is in particular smaller than <NUM>°, in particular smaller than <NUM>°, preferably smaller than <NUM>°.

Mounting system <NUM> holds optical elements <NUM> and <NUM> and amplifying unit <NUM>, in particular solid body <NUM>, in their positions.

For alignment of optical elements <NUM> and <NUM> and solid body <NUM> transverse to direction <NUM> of penetration, in particular in radial direction of main axes <NUM> and <NUM>, mounting system <NUM> comprises an alignment ring <NUM>, a wall <NUM> of which encloses an opening <NUM>.

For example wall <NUM> runs around an axis <NUM> of alignment, the axial direction of which corresponds to direction <NUM> of penetration, and axis <NUM> of alignment passes through opening <NUM>.

In particular wall <NUM> and opening <NUM> are rotational symmetric to axis <NUM> of alignment and axis <NUM> of alignment runs parallel to main axes <NUM> and <NUM> of optical elements <NUM> and <NUM>.

Region <NUM> of penetration passes through opening <NUM> of alignment ring <NUM>, such that penetrating radiation field <NUM> is free of interaction with alignment ring <NUM>.

In opening <NUM> solid body <NUM> and optical elements <NUM> and <NUM> are mounted with wall <NUM> holding these elements in radial direction to alignment axis <NUM>, in particular in region <NUM> of penetration.

Optical elements <NUM> and <NUM> as well as solid body <NUM> are part of connection <NUM> actuated by force of mounting system <NUM> and are such clamped by mounting system <NUM>.

Mounting system <NUM> comprises a first load element <NUM> and a second load element <NUM>, which are preferably shaped analogously, and with first load element <NUM> acting on optical element <NUM> and second load element <NUM> acting on optical element <NUM>.

Load element <NUM> is rotationally symmetrical to a loading axis <NUM>, which for example essentially coincides with main axis <NUM> of optical element <NUM> and load element <NUM> is rotationally symmetrical to a loading axis <NUM>, which for example essentially coincides with main axis <NUM> of optical element <NUM>, and in particular loading axes <NUM> and <NUM> essentially coincide.

Load element <NUM> presses, in particular in axial direction of main axis <NUM> on optical element <NUM> within an impact area <NUM>, which is at a distance to region <NUM> of penetration.

Impact area <NUM> is at first part <NUM> of optical element <NUM> and at a distance to region <NUM> of penetration.

Impact area <NUM> is symmetrical to main axis <NUM> of optical element <NUM>, for example runs in a radial distance around main axis <NUM>.

Load element <NUM> presses, in particular in axial direction of main axis <NUM>, on optical element <NUM> within an impact area <NUM>, which is at a distance to region <NUM> of penetration.

Impact area <NUM> is at second part <NUM> of optical element <NUM>. Impact area <NUM> is rotationally symmetrical to main axis <NUM> of optical element <NUM>, for example impact area <NUM> runs in a radial distance around main axis <NUM>.

Preferably impact areas <NUM> and <NUM> are shaped analogously with their positions being shifted with respect to direction <NUM> of penetration.

Accordingly load elements <NUM> and <NUM> clamp optical elements <NUM> and <NUM> and solid body <NUM> together.

Due to the corresponding design of optical element <NUM>, load element <NUM> and in particular impact area <NUM> on one hand and optical element <NUM>, load element <NUM> and in particular impact area <NUM> on the other hand, for example due to the with respect to symmetry plane <NUM> symmetrical design, optical elements <NUM> and <NUM> are exposed to comparable, in particular essentially the same, stress.

A strength of a force with which load element <NUM> acts on optical element <NUM> and a strength of a force with which load element <NUM> acts on optical element <NUM> are adjustable by mounting system <NUM> according to the preceding description and in particular the strength of these forces are the same due to connection <NUM>.

The action of mounting system <NUM>, in particular the impact of load elements <NUM> and <NUM>, induces strain in optical element <NUM> and strain in optical element <NUM> and as a result optical elements <NUM> and <NUM> become birefringent.

Accordingly, optical element <NUM> exposes a refractive index m1, which is due to the induced stress depending on a polarization of a radiation field, which penetrates optical element <NUM>.

Refractive index m1 adopts a value m1r for a radiation field with a polarization direction r1 and a value mia for a radiation field with a polarization direction a1 where directions r1 and a1 are essentially perpendicular to each other and to optical axis <NUM> and in particular run within disc plane <NUM>.

In particular due to the rotational symmetric design of optical element <NUM> and the rotational symmetrical action of mounting system <NUM> on optical element <NUM>, the stress induced birefringent action of optical element <NUM> is rotational symmetric to main axis <NUM>, too, that is direction r1 corresponds to the radial direction of main axis <NUM> and direction a1 runs perpendicular to direction r1, that is in azimuthal direction.

Second optical element <NUM> exposes a refractive index m2, which is due to the induced stress depending on a polarization of a radiation field, which penetrates optical element <NUM>, with refractive index m2 adopting a value m2r for a radiation field with a polarization direction r2 and a value m2a for a radiation field with a polarization direction a2, where directions r2 and a2 run perpendicular to each other and both directions run perpendicular to direction <NUM> of penetration, in particular directions r2 and a2 run within geometrical disc plane <NUM>.

In particular, due to the rotational symmetrical design of optical element <NUM> and the rotational symmetrical action of mounting system <NUM> on optical element <NUM>, the birefringent action of optical element <NUM> is rotational symmetrical to main axis <NUM>, too, so that direction r2 runs in radial direction to main axis <NUM> and direction a2 runs perpendicular to direction r2, that is in azimuthal direction.

Furthermore, due to the corresponding, in particular with respect to symmetry plane <NUM> symmetrical, arrangement of optical devices <NUM> and <NUM>, the values of m1r and m2r are essentially the same, for example differ with respect to each other by less than <NUM> %, and the values of mia and m2a are essentially the same, for example differ by less than <NUM> %, preferably and directions r1 and r2 point in essentially the same direction, for example in radial direction with respect to optical axis <NUM>, and directions a1 and a2 point in essentially the same direction, for example azimuthal around optical axis <NUM> with two directions pointing in essentially the same direction when an angle between these directions is for example smaller than <NUM>°, in particular smaller than <NUM>°, preferably smaller than <NUM>°.

When penetrating optical device <NUM> radiation field <NUM>, in particular a cross sectional area <NUM> of radiation field <NUM>, is exposed to polarization depending refractive index n1 of optical element <NUM>.

Accordingly, a component of radiation field <NUM> within cross sectional area <NUM>, which is polarized in polarization direction Pr, is exposed to refractive index m1r and a component of radiation field <NUM> within cross sectional area <NUM>, which is polarized in polarization direction Pa, is exposed to refractive index mia, where polarization directions Pr and Pa point in directions r1 and a1 respectively (<FIG>).

Due to the differing refractive indices, to which the components of radiation field <NUM> are exposed, optical path lengths for the two components through optical device <NUM> differ and the two components acquire a phase shift, that is their phases relative to each other differ.

Radiation field <NUM>, in particular within cross sectional area <NUM>, exits optical device <NUM> depolarized with respect to its initial polarization, that is radiation field <NUM> is, when exiting optical device <NUM>, not any more essentially linearly polarized in direction of initial polarization direction P, but has a component, which is polarized perpendicular to initial polarization direction P.

For example radiation field <NUM> is, when exiting optical device <NUM> elliptically polarized with a polarization direction P* rotating in a rotational direction <NUM> and a tip of a polarization vector moves along an ellipse (sketched in <FIG>).

After exiting optical device <NUM>, radiation field <NUM> enters amplifying unit <NUM> and by penetrating amplifying unit <NUM> radiation field <NUM> is exposed to polarization depending refractive index n of amplifying unit <NUM>.

A component of radiation field <NUM>, which is polarized in direction U1 is exposed to refractive index n1 and a component of radiation field <NUM> which is polarized in polarization direction U2 is exposed to refractive index n2.

Accordingly for two components of radiation field <NUM> optical path lengths through amplifying unit <NUM> differ, so that by penetrating amplifying unit <NUM> these two components acquire another phase shift.

Because amplifying unit <NUM> is designed as half wave plate the acquired phase shift corresponds essentially to half of the periodicity of radiation field <NUM>.

The birefringent impact of amplifying unit <NUM> corresponds essentially to mirroring the polarization of radiation field <NUM> at a plane, which is spanned by direction <NUM> of penetration and direction U2.

Accordingly, when exiting amplifying unit <NUM>, radiation field <NUM>, which has been elliptically polarized with rotating polarization direction P* when entering amplifying unit <NUM>, in particular within cross sectional area <NUM>, is elliptically polarized with a rotating polarization direction P**, which rotates in a rotational direction <NUM>, where rotational direction <NUM> is reversed to rotational direction <NUM>, and a tip of a corresponding polarization vector moves along an ellipse, which is mirrored to the ellipse corresponding to rotating polarization direction P* (sketched in <FIG>).

After exiting amplifying unit <NUM>, the polarized radiation field <NUM> enters optical device <NUM> and is exposed to polarization dependent refractive index m2 and acquires another depolarization.

By penetrating optical device <NUM>, in particular within cross sectional area <NUM>, a component of radiation field <NUM>, which is polarized in direction r2, is exposed to refractive index m2r and a component of radiation field <NUM>, which is polarized in direction a2, is exposed to refractive index m2a.

Accordingly, optical path lengths for two components through optical device <NUM> differ, such that these two components acquire another phase shift when penetrating optical device <NUM>.

Radiation field <NUM> exits optical device <NUM> polarized with a polarization direction P*** (sketched in <FIG>).

Due to the setup of amplifier system <NUM>, in particular due to the arrangement of optical devices <NUM> and <NUM>, amplifying unit <NUM> and mounting system <NUM>, the polarization of radiation field <NUM> when entering amplifier system <NUM>, that is with polarization direction P, is essentially the same as the polarization of radiation field <NUM> when exiting amplifier system <NUM> with a polarization direction P***, with these polarizations being essentially the same if the component of the radiation field <NUM>, which is polarized in direction of initial polarization direction P, contributes at least <NUM> % to the total radiation field <NUM> when exiting amplifier system <NUM>.

For the following reasons, polarization directions P and P*** are essentially the same.

The effect of optical device <NUM> to polarization field <NUM> is essentially the same as the effect of optical device <NUM> to polarization field <NUM>.

Radiation field <NUM> acquires when penetrating optical device <NUM> a component which is polarized perpendicular to polarization direction P and by penetrating optical device <NUM> radiation field <NUM> acquires a corresponding component which is perpendicular polarized to polarization direction P, because optical device <NUM> is essentially built up like optical device <NUM> and in particular because radiation field <NUM> is still mostly polarized in direction of polarization direction P.

But because radiation field <NUM> penetrated amplifying unit <NUM> before entering optical device <NUM>, the component of radiation field <NUM>, which is induced by optical device <NUM> and polarized perpendicular to polarization direction P, is inverted.

In consequence, the component of radiation field <NUM>, which is induced by optical device <NUM> and inverted by amplifying unit <NUM>, essentially compensates, that is cancels, the component, which is induced by optical device <NUM>.

Pumping device <NUM> comprises a source of energy and provides energy to amplifying unit <NUM> for amplifying radiation field <NUM>.

For example pumping device <NUM> comprises a source, which generates a pumping radiation field <NUM> and pumping radiation field <NUM> penetrates amplifying unit <NUM>, in particular solid body <NUM>.

For example pumping radiation field <NUM> is introduced to amplifying unit <NUM> oblique to direction <NUM> of penetration of radiation field <NUM> such that pumping radiation field <NUM> penetrates solid body <NUM> in region <NUM> of penetration but outside of solid body <NUM> radiation field <NUM> and pumping radiation field <NUM> do not run through each other.

Preferably, pumping device <NUM> comprises a multiple path arrangement for guiding pumping radiation field <NUM> several times through solid body <NUM> to increase the efficiency of pumping by pumping radiation field <NUM>.

When penetrating solid body <NUM> pumping radiation field <NUM> excites laser active transition in the laser active material of solid body <NUM> and radiation field <NUM> is amplified by stimulated emission of these excited laser active transitions.

Heat dissipation system <NUM> comprises a first heat spreading element <NUM> and a second heat spreading element <NUM>, which conduct heat from amplifying unit <NUM> to a first heat sink <NUM> and a second heat sink <NUM> and accordingly prevent overheating of amplifying unit <NUM>.

For example, heat spreading element <NUM>, <NUM> comprise diamond, preferably monocrystalline diamond.

In the present embodiment (<FIG>) heat spreading elements <NUM> and <NUM> are built analogously, such that heat spreading elements <NUM> and <NUM> are described in the following together as far as it is possible and for parts of heat spreading elements <NUM> and <NUM>, which are built the same, the same reference signs are used, such that the corresponding description completely applies to both heat spreading elements <NUM> and <NUM> and for corresponding parts of heat spreading elements <NUM> and <NUM>, which are built differently in these elements <NUM> and <NUM>, or in cases in which a particular part of either first heat spreading element <NUM> or second heat spreading element <NUM> are meant, a suffix I is added to the corresponding reference sign to designate the corresponding part as a part of first heat spreading element <NUM> and a suffix II is added to the corresponding reference sign to designate the corresponding part as a part of second heat spreading element <NUM>.

In the present embodiment heat spreading element <NUM> corresponds to optical element <NUM> and heat spreading element <NUM> corresponds to optical element <NUM> such that regarding the description of heat spreading elements <NUM>, <NUM> it is completely referred to the description of optical elements <NUM>, <NUM> and vice versa.

Heat spreading element <NUM>, <NUM>, exemplarily shown in <FIG>, comprises a contact part <NUM>, which is in thermal contact with amplifying unit <NUM>, in particular with solid body <NUM>.

Within a rising area <NUM> contact part <NUM> rises over a geometrical reference plane <NUM>, such that a contact surface <NUM> of heat spreading element <NUM>, <NUM> at contact part <NUM> has within rising area <NUM> different distances d, d' from geometrical reference plane <NUM> at different positions in rising area <NUM>.

Contact part <NUM> is thinnest in an outer area <NUM> and is thickest in a central area <NUM> with a thickness of contact part <NUM> being for example measured with respect to geometrical reference plane <NUM> and in particular in a part of outer area <NUM> contact surface <NUM> is at the level of geometrical reference plane <NUM>.

Through central area <NUM> a central axis <NUM> runs, which is for example perpendicular to geometrical reference plane <NUM>, and outer area <NUM> is at a distance from central axis <NUM> and preferably contact part <NUM> is rotational symmetrical to central axis <NUM>.

Preferably, central axis <NUM> is essentially parallel to optical axis <NUM>, that is an angle between axes <NUM> and <NUM> is smaller than <NUM>°, in particular smaller than <NUM>°, preferably smaller than <NUM>°.

Outer area <NUM> in particular surrounds central area <NUM> and runs around central axis <NUM>.

Contact part <NUM> becomes thicker, in particular continuously thicker, upon approaching central area <NUM> from outer area <NUM> that is upon decreasing the radial distance to central axis <NUM>.

Accordingly, contact surface <NUM> of heat spreading element <NUM>, <NUM> moves, in particular continuously increasing, away from geometrical reference plane <NUM> upon running from outer area <NUM> towards central area <NUM>, such that the distance d between contact surface <NUM> and geometrical reference plane <NUM> increases, in particular continuously, between outer area <NUM> and central area <NUM> with the distance d being smaller in outer area <NUM> than in central area <NUM> and in particular with distance d approaching its maximal value within central area <NUM>.

In other words a measured value of the distance d between geometrical reference plane <NUM> and contact surface <NUM> of heat spreading element <NUM>, <NUM> increases, in particular continuously, upon moving a point of measurement, at which the distance d is measured, from outer area <NUM> towards central area <NUM>, in particular upon moving the point of measurement radially towards central axis <NUM>.

Contact surface <NUM> is curved with a radius Q of curvature and contact part <NUM> is within rising area <NUM> convex.

Radius Q of curvature is significantly larger, for example at least <NUM> times larger, than an extension C of heat spreading element <NUM>, <NUM> within geometrical reference plane <NUM>, where the distance between outer area <NUM> and central area <NUM> is for example half of the extension C, with the distance between outer area <NUM> and central area <NUM> being for example measured from central axis <NUM> in radial direction to the point at which contact surface <NUM> reaches geometrical reference plane <NUM>, for example crosses geometrical reference plane <NUM>.

Heat spreading element <NUM>, <NUM> extends from contact part <NUM> across geometrical reference plane <NUM>, in particular in axial direction of central axis <NUM>, to a second part <NUM>.

A thickness T of heat spreading element <NUM>, <NUM> is measured from contact part <NUM> to second part <NUM>.

For example the thickness T of heat spreading element <NUM>, <NUM> is smaller than the extension C of heat spreading element <NUM>, <NUM>.

A surface <NUM> of heat spreading element <NUM>, <NUM> at second part <NUM> is for example planar that is surface <NUM> extends essentially in a geometrical plane which in particular is parallel to geometrical reference plane <NUM>.

A distance between surfaces <NUM> and <NUM> at contact part <NUM> and second part <NUM>, respectively, corresponds essentially to thickness T of heat spreading element <NUM> with the distance between surfaces <NUM> and <NUM> varies along the extension of these surfaces because of the rising of contact part <NUM>.

The variation of the distance between the surfaces <NUM> and <NUM> is however small, for example a maximal and minimal value of that distance differ with respect to a mean value of the distance by less than <NUM> %, in particular less than <NUM>,<NUM> %.

Further, in the present embodiment the description of optical elements <NUM>, <NUM> completely corresponds to the description of heat spreading elements <NUM>, <NUM> and vice versa with central axis 538I of heat spreading element <NUM> and central axis 528II of heat spreading element <NUM> corresponding to main axis <NUM> of optical element <NUM> and main axis <NUM> of optical element <NUM>, respectively, and second part 542I and contact part 522I of heat spreading element <NUM> corresponding to first part <NUM> and second side <NUM> of optical element <NUM> as well as contact part 522II and second part 542II of heat spreading element <NUM> corresponding to first part <NUM> and second part <NUM> of optical element <NUM>.

Mounting system <NUM> acts on heat spreading element <NUM>, <NUM>, in particular on an impact area <NUM>, to hold heat spreading element <NUM>, <NUM> in its position and to press heat spreading element <NUM>, <NUM> against amplifying unit <NUM>.

Preferably, impact area <NUM> runs in a radial distance around central axis <NUM>.

In particular, impact area <NUM> encircles region <NUM> of penetration.

Heat spreading element <NUM> is pressed by mounting system <NUM> with contact part 522I against amplifying unit <NUM>, in particular against first side <NUM> of solid body <NUM> and second heat spreading element <NUM> is pressed by mounting system <NUM> with contact part 522II against amplifying unit <NUM>, in particular against second side <NUM> of solid body <NUM>.

A loading element <NUM> of mounting system <NUM> acts on heat spreading element <NUM> to press heat spreading element <NUM> with a contact area <NUM> against amplifying unit <NUM> and a loading element <NUM> of mounting system <NUM> acts on heat spreading element <NUM> to press heat spreading element <NUM> with a contact area <NUM> against amplifying unit <NUM>.

Loading elements <NUM> and <NUM> are built analogously and act in an analogous way on heat spreading elements <NUM> and <NUM>, respectively, such that these elements and their action on heat spreading elements <NUM> and <NUM> are described together as far as it is possible and for parts of loading elements <NUM> and <NUM>, which are built the same, the same reference signs are used with the corresponding description completely applies to both loading elements <NUM>, <NUM> and where loading elements <NUM>, <NUM> are different or where the description distinguishes between loading elements <NUM> and <NUM> a suffix I at a reference sign is used to indicate the corresponding part as a part of loading element <NUM> and a suffix II at the reference sign indicates the corresponding part as a part of loading element <NUM>.

In the present embodiment, loading element <NUM> corresponds to load element <NUM> and loading element <NUM> corresponds to load element <NUM>, such that regarding the description of loading element <NUM> and <NUM> it is also completely referred to the description of load elements <NUM> and <NUM> and vice versa.

In particular, loading elements <NUM>, <NUM> are also part of said heat dissipation system <NUM> and conduct heat from said heat spreading elements <NUM>, <NUM> to a cooling system.

For example said loading elements <NUM>, <NUM> comprise diamond, preferably polycrystalline diamond.

Heat spreading element <NUM>, <NUM> is aligned, such that it is pressed with its central area <NUM> against amplifying unit <NUM>, in particular against side <NUM>, <NUM> of solid body <NUM>, such that central area 536I of heat spreading element <NUM> overlaps with contact area <NUM> between heat spreading element <NUM> and amplifying unit <NUM> and central area 536II of heat spreading element <NUM> overlaps with contact area <NUM> between heat spreading element <NUM> and amplifying unit <NUM>.

Because heat spreading element <NUM>, <NUM> is pressed with its contact part <NUM> against amplifying unit <NUM> the distance d between contact surface <NUM> and geometrical reference plane <NUM> is reduced with respect to an unloaded state, that is in particular an unpumped state and an external force free state.

Because of the non-planar contact surface <NUM> of contact part <NUM>, a partial force acting between a partial area of contact part <NUM> and amplifying unit <NUM> differs for different partial areas, such that a non-uniform pressure profile develops in contact area <NUM>, <NUM> between heat spreading element <NUM>, <NUM> and amplifying unit <NUM> and furthermore the distance d between contact surface <NUM> and geometrical reference plane <NUM> gets non-uniformly smaller across contact part <NUM>.

Due to the non-planar contact surface <NUM> contact part <NUM> adheres to amplifying unit <NUM>, in particular to solid body <NUM>, that is contact part <NUM> is closely attached to solid body <NUM> with a particular smooth, distortion free interface between contact part <NUM> and solid body <NUM>.

The force with which loading element <NUM>, <NUM> presses on heat spreading element <NUM>, <NUM> is guided due to the curved contact surface <NUM> of contact part <NUM> from impact area <NUM>, which is for example opposite to outer area <NUM>, where outer area <NUM> is in particular apart from solid body <NUM>, to contact area <NUM>, <NUM> and accordingly this force presses heat spreading element <NUM>, <NUM> closely to amplifying unit <NUM>.

Therefore a bending of heat spreading element <NUM>, <NUM> and consequently a detachment of contact part <NUM> in contact area <NUM>, <NUM> from amplifying unit <NUM> due to a turning away from, at least a part of, contact area <NUM>, <NUM> induced by the bending of heat spreading element <NUM>, <NUM> is avoided.

Contact areas <NUM> and <NUM> are aligned, such that they are within region <NUM> of penetration, so that radiation field <NUM> passes through contact areas <NUM> and <NUM> and accordingly through the, in particular smooth, interfaces between contact parts 522I, 522II on one hand and amplifying unit <NUM> on the other hand.

Accordingly, radiation field <NUM> penetrates heat spreading elements <NUM>, <NUM>.

Diffraction losses in radiation field <NUM> are in particular reduced due to the against amplifying unit <NUM> pressed contact part <NUM>, in particular the smooth interface between contact part <NUM> and amplifying unit <NUM> within contact area <NUM>, <NUM>.

By adjusting the strength of the force, with which heat spreading element <NUM>, <NUM> is pressed against amplifying unit <NUM>, the reduction of diffraction losses can be further reduced.

For adjusting heat spreading elements <NUM> and <NUM>, in particular to adjust contact areas <NUM> and <NUM> to be aligned in region <NUM> of penetration, amplifier system <NUM> comprises an adjustment system <NUM>, which is for example a part of mounting system <NUM>.

Adjustment system <NUM> comprises an adapting element <NUM>, which sits in a seat <NUM>, and a tuning unit <NUM> (<FIG>).

Adapting element <NUM> is ring-like shaped and extends essentially in an geometrical adjustment plane <NUM>, which is perpendicular to an adjustment axis <NUM>, and adjustment axis <NUM> essentially coincides in particular with main axes <NUM>, <NUM> and housing axis <NUM>.

Adapting element <NUM> runs around adjustment axis <NUM> with a surface at a first side <NUM> running essentially parallel to geometrical adjustment plane <NUM> and a surface at a second side <NUM> running oblique to geometrical adjustment plane <NUM> and consequently oblique to the surface at first side <NUM>, such that adapting element <NUM> gets narrower with increasing radial distance from adjustment axis <NUM>.

Second side <NUM> of adapting element <NUM> sits in seat <NUM> and first side <NUM> is linked to loading element <NUM>.

Seat <NUM> is loaded on one side by spring <NUM> and receives adapting element <NUM> at a supporting side <NUM>, the surface of which is in particular accordingly shaped to the surface of adapting element <NUM> at second side <NUM> that is correspondingly angled to geometrical adjustment plane <NUM>.

Tuning unit <NUM> acts on adapting element <NUM> to tune the position of adapting element <NUM> in radial direction to adjustment axis <NUM>.

For example, tuning unit <NUM> comprises several adjusting screws, which are connected to housing <NUM> and act on adapting element <NUM> in radial direction to adjustment axis <NUM>.

In this way, adapting element <NUM> sits, in particular in axial direction to adjustment axis <NUM>, between seat <NUM> and loading element <NUM> and is consequently a part of connection <NUM> actuated by force.

By tuning the position of adapting element <NUM> in radial direction of adjustment axis <NUM>, the distance between seat <NUM> and loading element <NUM> is adjusted, due to the narrowing of adapting element <NUM> in radial direction of adjustment axis <NUM>.

With tuning unit <NUM>, the radial position of adapting element <NUM> at different positions around adjustment axis <NUM> is tunable, for example by several adjusting screws in housing <NUM>.

Accordingly loading element <NUM> is tilted with respect to geometrical adjustment plane <NUM> and transfers this tiltment to heat spreading element <NUM> and the tiltment of heat spreading element <NUM> results in a tiltment of contact part 522I of heat spreading element <NUM> and accordingly contact area <NUM> between contact part 522I and amplifying unit <NUM> is shifted.

In another embodiment, a resonator <NUM>, which is exemplarily shown in <FIG>, comprises a first mirror <NUM> and a second mirror <NUM> and an amplifier system <NUM>' according to the preceding embodiment.

A radiation field <NUM>' is reflected by first mirror <NUM> towards second mirror <NUM> and is reflected by second mirror <NUM> towards first mirror <NUM>.

Accordingly radiation field <NUM>' extends in between first mirror <NUM> and second mirror <NUM> and amplifier system <NUM>' is located between first mirror <NUM> and second mirror <NUM>, such that radiation field <NUM>' penetrates amplifier system <NUM>' when passing from one of the mirrors <NUM>, <NUM> to the other mirror <NUM>, <NUM>.

In particular first mirror <NUM> is highly refractive, such that most of radiation field <NUM>' is reflected, for example at least <NUM> % of radiation field <NUM>' are reflected by first mirror <NUM>.

Claim 1:
Radiation field amplifier system (<NUM>) for a radiation field (<NUM>) comprising an amplifying unit (<NUM>) and a heat dissipation system (<NUM>) with one heat spreading element (<NUM>, <NUM>) or several heat spreading elements (<NUM>, <NUM>), and a first optical device and a second optical device wherein said first and second optical devices are part of said heat dissipation system and said radiation field penetrates said first optical device, said amplifying unit and said second optical device in this order,
wherein said one heat spreading element (<NUM>, <NUM>) or at least one of said several heat spreading elements (<NUM>, <NUM>) of said heat dissipation system (<NUM>) is an element of one of said first and said second optical devices and is pressed with a contact surface (<NUM>) within a contact area (<NUM>, <NUM>) against said amplifying unit (<NUM>) and said contact surface (<NUM>) rises starting from a geometrical reference plane (<NUM>) in direction towards said amplifying unit (<NUM>) and a distance d between said contact surface (<NUM>) and said geometrical reference plane (<NUM>) attains its largest value within a central area (<NUM>, <NUM>, <NUM>), which is arranged inside said contact area (<NUM>, <NUM>) and said distance d is smaller outside said central area (<NUM>, <NUM>, <NUM>) than inside said central area (<NUM>, <NUM>, <NUM>), wherein a region (<NUM>) of penetration of said radiation field (<NUM>) passes through said contact area (<NUM>, <NUM>), within which said one heat spreading element (<NUM>, <NUM>) or one of said several heat spreading elements (<NUM>, <NUM>) is pressed against said amplifying unit (<NUM>), and
wherein said amplifier system comprises a source of a pumping radiation field and said pumping radiation field provides pumping energy to said amplifying unit.