Light emitting device and projector

A light emitting device includes resonant parts constituted by a photonic crystal structure, and rows each of which includes the resonant parts arranged along a first direction, wherein light resonating in the resonant part resonates in a first resonant direction and a second resonant direction, the rows are arranged along a second direction, the rows include a first row, and a second row, a distance between the resonant part located furthest at one side of the first direction in the first row and the resonant part located furthest at the one side of the first direction in the second row is different from a distance between the resonant part located furthest at the one side of the first direction and the resonant part located furthest at another side of the first direction in the first row, the first and second resonant directions are along the first and second axes respectively, and in a plan view a length along the first direction of the resonant part and a length along the second direction of the resonant part are equal to each other.

The present application is based on, and claims priority from JP Application Serial Number 2019-139486, filed Jul. 30, 2019, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a light emitting device and a projector.

2. Related Art

A projector using a semiconductor laser element as a light source has been put into practical use.

In JP-A-2013-190591, for example, there is described a projector provided with a red light source device, a blue light source device, and a green light source device formed of a fluorescence emitting device which is excited by outgoing light from an excitation light source device.

As a light source of such a projector as described above, there is demanded a light emitting device for emitting light having an isotropic light distribution angle. When using the light emitting device for emitting the light having the isotropic light distribution angle, since the cross-sectional shape is a circular shape, and thus, the light having a homogenous intensity distribution can be obtained, it is possible to efficiently excite a phosphor when, for example, exciting the phosphor.

SUMMARY

A light emitting device according to an aspect of the present disclosure includes p resonators each having a resonant part constituted by a photonic crystal structure, wherein light resonating in the resonant part resonates in a plurality of resonant directions, in the resonant part, lengths in the plurality of resonant directions are all equal to each other, q of the resonant parts are arranged along a first direction to form a row, the rows are arranged along a second direction as much as r, p=qλr is true, a distance between the resonant part located furthest at one side of the first direction in the row located furthest at one side of the second direction of the r rows and the resonant part located furthest at the one side of the first direction in the row located furthest at another side of the second direction of the r rows is different from a distance between the resonant part located furthest at the one side of the first direction and the resonant part located furthest at another side of the first direction in the row located furthest at the one side of the second direction of the r rows, the plurality of resonant directions includes a direction along the first direction and a direction along the second direction, and in a plan view viewed from a direction along a third direction perpendicular to a plane including the first direction and the second direction, a length along the first direction of the resonant part and a length along the second direction of the resonant part are equal to each other.

In the light emitting device according to the above aspect, nano-structures of the photonic crystal structure may be arranged so as to form a square lattice, the first direction and the second direction may be perpendicular to each other, and the plurality of resonant directions may correspond to the direction along the first direction and the direction along the second direction.

In the light emitting device according to the above aspect, nano-structures of the photonic crystal structure may be arranged so as to form an equilateral-triangular lattice, the second direction may be tilted 120° with respect to the first direction, and the plurality of resonant directions may correspond to a direction along the first direction, a direction along the second direction, and a direction along a fourth axis tilted 60° with respect to the first direction.

A projector according to another aspect of the present disclosure includes the light emitting device according to one of the above aspects.

The projector according to the above aspect may further include a light collection optical system configured to collect light emitted from the light source device, and a phosphor to be excited by light emitted from the light collection optical system.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Some preferred embodiments of the present disclosure will hereinafter be described in detail using the drawings. It should be noted that the embodiments described hereinafter do not unreasonably limit the contents of the present disclosure as set forth in the appended claims. Further, all of the constituents described hereinafter are not necessarily essential elements of the present disclosure.

1. First Embodiment

1.1. Light Emitting Device

Firstly, a light emitting device according to a first embodiment will be described with reference to the drawings.FIG. 1is a plan view schematically showing the light emitting device100according to the first embodiment, namely the present embodiment. It should be noted that inFIG. 1, a first direction A1, a second direction A2, and a third direction A3are shown as three axes crossing each other. In the illustrated example, the first direction A1, the second direction A2, and the third direction A3are perpendicular to each other.

As shown inFIG. 1, the light emitting device100has resonators12each having a resonant part10. The light emitting device100has p pieces of the resonators12. In other words, the light emitting device100has p pieces of the resonant parts10. In the illustrated example, the light emitting device100has 64 resonant parts10. The resonant part10is a part where the light resonates.

A row11of the resonant parts10is formed by q of the resonant parts10arranged along the first direction A1. In the illustrated example, the row11of the resonant parts10is formed by 16 of the resonant parts10arranged along the first direction A1. There are arranged the rows as much as r along the second direction A2. In the illustrated example, there are arranged the rows11as much as 4 along the second direction A2. It should be noted that p=q×r is true. In the illustrated example, the p resonant parts10are arranged in a matrix in a direction along the first direction A1and a direction along the second direction A2. The p resonant parts10are, for example, the same in shape and size.

A row11ais a first row which is one of the r rows11, and is located the furthest at one side (in the +A2axis direction in the illustrated example) of the second direction A2. A resonant part10ais one of the resonant parts10, and is located the furthest at one side (in the +A1axis direction in the illustrated example) of the first direction A1in the row11a. A resonant part10bis one of the resonant parts10, and is located the furthest at the other side (in the −A1axis direction in the illustrated example) of the first direction A1in the row11a.

A row11bis a second row which is one of the r rows11, and is located the furthest at the other side (in the −A2axis direction in the illustrated example) of the second direction A2. A resonant part10cis one of the resonant parts10, and is located the furthest at the one side (in the +A1axis direction in the illustrated example) of the first direction A1in the row11b.

A distance D1between the resonant part10aand the resonant part10cand a distance D2between the resonant part10aand the resonant part10bare different from each other. In a plan view (hereinafter simply referred to as “in the plan view”) viewed from a direction along the third direction A3perpendicular to a plane including the first direction A1and the second direction A2, a distance between the center of the resonant part10aand the center of the resonant part10cis different from a distance between the center of the resonant part10aand the center of the resonant part10b. In the illustrated example, the distance D1between the resonant part10aand the resonant part10cis shorter than the distance D2between the resonant part10aand the resonant part10b.

Here,FIG. 2is the plan view schematically showing the light emitting device100according to the first embodiment, namely the present embodiment.FIG. 3is a cross-sectional view along the line III-III shown inFIG. 2, and schematically shows the light emitting device100according to the first embodiment, namely the present embodiment.

As shown inFIG. 2andFIG. 3, the light emitting device100has, for example, a substrate102, a stacked body103disposed on the substrate102, a first electrode122, and a second electrode124. The stacked body103has a reflecting layer104, a buffer layer106, a photonic crystal structure108, and a semiconductor layer120. It should be noted that inFIG. 1, the light emitting device100is illustrated in a simplified manner for the sake of convenience. Further, inFIG. 2, the illustration of members other than columnar parts110of the photonic crystal structure108is omitted.

The substrate102is, for example, an Si substrate, a GaN substrate, or a sapphire substrate.

The reflecting layer104is disposed on the substrate102. The reflecting layer104is, for example, a DBR (distributed Bragg reflector) layer. The reflecting layer104is, for example, what is obtained by alternately stacking AlGaN layers and GaN layers at one another or what is obtained by alternately stacking AlInN layers and GaN layers on one another. The reflecting layer104reflects the light generated by a light emitting layer114of each of columnar parts110of the photonic crystal structure108toward the second electrode124.

It should be noted that in the present specification, when taking the light emitting layer114as a reference in the stacking direction (hereinafter also referred to simply as a “stacking direction”) of the stacked body103, the description will be presented assuming a direction from the light emitting layer114toward a semiconductor layer116as an “upward direction,” and a direction from the light emitting layer114toward a semiconductor layer112as a “downward direction.” Further, the “stacking direction of the stacked body” denotes a stacking direction of the semiconductor layer112and the light emitting layer114.

The buffer layer106is disposed on the reflecting layer104. The buffer layer106is a layer made of semiconductor such as an Si-doped n-type GaN layer. In the illustrated example, on the buffer layer106, there is disposed a mask layer128for growing the columnar parts110. The mask layer128is, for example, a silicon oxide layer or a silicon nitride layer.

The photonic crystal structure108is disposed on the buffer layer106. The photonic crystal structure108has, for example, the columnar parts110and light propagation layers118.

The photonic crystal structure108can develop an effect of the photonic crystal, and the light emitted by the light emitting layers114of the photonic crystal structure108is confined in an in-plane direction of the substrate102, and is emitted in the stacking direction. Here, the “in-plane direction of the substrate102” denotes a direction perpendicular to the stacking direction.

The columnar parts110are disposed on the buffer layer106. The planar shape of the columnar part110is a polygonal shape such as a regular hexagon, a circle, or the like. In the example shown inFIG. 2, the planar shape of the columnar part110is a regular hexagon. The diametrical size of the columnar part110is, for example, in a nanometer-order range, and is specifically not smaller than 10 nm and not larger than 500 nm. The columnar part110is a nano-structure constituting the photonic crystal structure108. The size in the stacking direction of the columnar part110is, for example, not smaller than 0.1 μm and not larger than 5 μm.

It should be noted that when the planar shape of the columnar part110is a circle, the “diametrical size” denotes the diameter of the circle, and when the planar shape of the columnar part110is not a circle, the “diametrical size” denotes the diameter of a minimum enclosing circle. For example, when the planar shape of the columnar part110is a polygonal shape, the diametrical size of the columnar part110is the diameter of a minimum circle including the polygonal shape inside, and when the planar shape of the columnar part110is an ellipse, the diametrical size of the columnar part110is the diameter of a minimum circle including the ellipse inside. Further, when the planar shape of the columnar part110is a circle, the “center of the columnar part110” denotes the center of the circle, and when the planar shape of the columnar part110is not a circle, the “center of the columnar part110” denotes the center of the minimum enclosing circle. For example, when the planar shape of the columnar part110is a polygonal shape, the center of the columnar part110is the center of a minimum circle including the polygonal shape inside, and when the planar shape of the columnar part110is an ellipse, the center of the columnar part110is the center of a minimum circle including the ellipse inside.

The number of the columnar parts110disposed is more than one. An interval between the columnar parts110adjacent to each other is, for example, not smaller than 1 nm and not larger than 500 nm. The columnar parts110are periodically disposed in a predetermined direction at a predetermined pitch.

In the example shown inFIG. 2, the columnar parts110are arranged so as to form a square lattice. In the illustrated example, the columnar parts110are arranged along the first direction A1at a predetermined pitch, and are arranged along the second direction A2at a predetermined pitch. The pitch along the first direction A1of the columnar parts110and the pitch along the second direction A2of the columnar parts110are equal to each other. The pitch along the first direction A1of the columnar parts110mentioned here is a distance between the centers of the columnar parts110adjacent to each other along the first direction A1. The pitch along the second direction A2of the columnar parts110means a distance between the centers of the columnar parts110adjacent to each other along the second direction A2.

As shown inFIG. 3, the columnar parts110each have the semiconductor layer112, the light emitting layer114, and the semiconductor layer116.

The semiconductor layer112is disposed on the buffer layer106. The semiconductor layer112is, for example, the Si-doped n-type GaN layer.

The light emitting layer114is disposed on the semiconductor layer112. The light emitting layer114is disposed between the semiconductor layer112and the semiconductor layer116. The light emitting layer114has a quantum well structure constituted by, for example, a GaN layer and an InGaN layer. The light emitting layer114is a layer capable of emitting light in response to injection of an electrical current.

The semiconductor layer116is disposed on the light emitting layer114. The semiconductor layer116is a layer different in conductivity type from the semiconductor layer112. The semiconductor layer116is, for example, an Mg-doped p-type GaN layer. The semiconductor layers112,116are cladding layers having a function of confining the light in the light emitting layer114.

The light propagation layer118is disposed between the columnar parts110adjacent to each other. In the illustrated example, the light propagation layers118are disposed on the mask layer128. The refractive index of the light propagation layer118is lower than, for example, the refractive index of the light emitting layer114. The light propagation layer118is, for example, a silicon oxide layer, an aluminum oxide layer, or a titanium oxide layer. The light generated in the light emitting layer114can propagate through the light propagation layer118.

The resonant part10is constituted by the photonic crystal structure108. The p resonant parts10are separated from each other. In the illustrated example, the columnar part110is not disposed between the resonant parts10adjacent to each other. The p resonant parts10have a single substrate102as a common substrate. In the resonant parts10adjacent to each other, the light resonating in one of the resonant parts10does not reach the other of the resonant parts10. The distance between the resonant parts10adjacent to each other is longer than the wavelength of the light generated in the light emitting layer114. Thus, in the resonant parts10adjacent to each other, it is possible to prevent the light resonating in one of the resonant parts10from reaching the other of the resonant parts10.

It should be noted that although not shown in the drawings, it is possible to dispose a light absorption part for absorbing light between the resonant parts10adjacent to each other. The light absorption part is formed of a substance having a narrower bandgap than the light resonating in the resonant part10. As the substance, there can be cited, for example, InGaN and InN. The light absorption part is, for example, a crystalline body having a columnar shape or a wall-like shape. Thus, in the resonant parts10adjacent to each other, it is possible to prevent the light resonating in one of the resonant parts10from reaching the other of the resonant parts10.

Further, although not shown in the drawings, it is possible to dispose a light reflection part for reflecting light between the resonant parts10adjacent to each other. For example, by disposing the columnar parts110smaller in pitch and diametrical size than the columnar parts110constituting the resonant part10between the resonant parts10adjacent to each other, it is possible to form the light reflection part. Thus, in the resonant parts10adjacent to each other, it is possible to prevent the light resonating in one of the resonant parts10from reaching the other of the resonant parts10.

In the plan view, a length L1along the first direction A1of the resonant part10and a length L2along the second direction A2of the resonant part10are equal to each other. Since the length L1and the length L2are equal to each other, as shown inFIG. 4, in the light emitted from the resonant part10, a light distribution angle θ1along the first direction A1and a light distribution angle θ2along the second direction A2become equal to each other. As described above, it is possible to check whether or not the length L1and the length L2are equal to each other based on the light distribution angle of the light emitted from the resonant part10.

In the plan view, the shape of the resonant part10is, for example, a square. In the plan view, a diagram formed of straight lines connecting the centers of the columnar parts110located at the outermost circumference out of the plurality of columnar parts110constituting the resonant part10is, for example, a square. When the diagram is a square or a regular hexagon, the light emitted from the resonant part10becomes to have a light distribution angle which is rotational symmetry with respect to an emission axis a as shown inFIG. 4. In the illustrated example, the emission axis a is an axis parallel to the third direction A3.

The light resonating in the resonant part10resonates in a plurality of resonant directions. In the resonant part10, the lengths in the plurality of resonant directions are all equal to each other. It is possible to check whether or not the lengths in the resonant directions in the resonant part10are all equal to each other based on the light distribution angle of the light emitted from the resonant part10. The plurality of resonant directions includes a first resonant direction along the first direction A1and a second resonant direction along the second direction A2. In the illustrated example, the plurality of resonant directions comprises the direction along the first direction A1and the direction along the second direction A2. In the plan view, for example, in the resonant part10, a distance between the center of the columnar part110located the furthest at the one side of the first direction A1and the center of the columnar part110located the furthest at the other side of the first direction A1is equal to a distance between the center of the columnar part110located the furthest at the one side of the second direction A2and the center of the columnar part110located the furthest at the other side of the second direction A2.

For example, as shown inFIG. 1, a distance between the center of the columnar part110located the furthest in the −A2axis direction out of the plurality of columnar parts110constituting the resonant part10aand the center of the columnar part110located the furthest in the +A2axis direction out of the plurality of columnar parts110constituting the resonant part10cis different from a distance between the center of the columnar part110located the furthest in the −A1axis direction out of the plurality of columnar parts110constituting the resonant part10aand the center of the columnar part110located the furthest in the +A1axis direction out of the plurality of columnar parts110constituting the resonant part10b.

In the light emitting device100, the p-type semiconductor layer116, the light emitting layer114with no impurity doped, and the n-type semiconductor layer112constitute a pin diode. The semiconductor layers112,116are layers larger in bandgap than the light emitting layer114. In the light emitting device100, when applying a forward bias voltage of the pin diode between the first electrode122and the second electrode124to inject a current, there occurs recombination of electrons and holes in the light emitting layer114. The recombination causes light emission. The light generated in the light emitting layer114propagates through the light propagation layer118in the in-plane direction of the substrate102due to the semiconductor layers112,116to form a standing wave due to the effect of the photonic crystal in the photonic crystal structure108, and is confined in the in-plane direction of the substrate102. The light thus confined causes laser oscillation with the gain in the light emitting layer114. In other words, the light generated in the light emitting layer114resonates in the in-plane direction of the substrate102due to the photonic crystal structure108to cause the laser oscillation. Specifically, the light generated in the light emitting layer114resonates in the in-plane direction of the substrate102in the resonant part10of the resonator12constituted by the photonic crystal structure108to cause the laser oscillation. Then, positive first-order diffracted light and negative first-order diffracted light proceed in the stacking direction as a laser beam.

The laser beam proceeding toward the reflecting layer104out of the laser beam having proceeded in the stacking direction is reflected by the reflecting layer104, and proceeds toward the second electrode124. Thus, it is possible for the light emitting device100to emit the light from the second electrode124side.

The semiconductor layer120is disposed on the photonic crystal structure108. The semiconductor layer120is, for example, an Mg-doped p-type GaN layer.

The first electrode122is disposed on the buffer layer106. It is also possible for the buffer layer106to have ohmic contact with the first electrode122. In the illustrated example, the first electrode122is electrically coupled to the semiconductor layer112via the buffer layer106. The first electrode122is one of the electrodes for injecting the electrical current into the light emitting layer114. As the first electrode122, there is used, for example, what is obtained by stacking a Ti layer, an A1layer, and an Au layer in this order from the buffer layer106side.

The second electrode124is disposed on the semiconductor layer120. It is also possible for the semiconductor layer120to have ohmic contact with the second electrode124. The second electrode124is electrically coupled to the semiconductor layer116. In the illustrated example, the second electrode124is electrically coupled to the semiconductor layer116via the semiconductor layer120. The second electrode124is the other of the electrodes for injecting the electrical current into the light emitting layer114. As the second electrode124, there is used, for example, ITO (Indium Tin Oxide). The second electrode124disposed in one of the photonic crystal structures108adjacent to each other and the second electrode124disposed in the other of the photonic crystal structure are electrically coupled to each other with an interconnection not shown.

It should be noted that although the light emitting layer114of the InGaN type is described above, any types of material capable of emitting light in response to an electrical current injected in accordance with the wavelength of the light emitted can be used as the light emitting layer114. It is possible to use semiconductor materials such as an AlGaN type, an AlGaAs type, an InGaAs type, an InGaAsP type, an InP type, a GaP type, or an AlGaP type. Further, it is also possible to change the size and the pitch of the arrangement of the columnar parts110in accordance with the wavelength of the light emitted.

Further, although the photonic crystal structure108has the columnar parts110disposed periodically in the above description, it is also possible to have hole parts disposed periodically as a nano-crystal structure in order to develop the photonic crystal effect.

The light emitting device100has, for example, the following advantages.

In the light emitting device100, there are provided the resonators12each having the resonant part10constituted by the photonic crystal structure108, and in the plan view, the length L1along the first direction A1of the resonant part10and the length L2along the second direction A2of the resonant part10are equal to each other. Therefore, in the light emitting device100, it is possible to make the light distribution angle along the first direction A1and the light distribution angle along the second direction A2equal to each other in the light to be emitted from the resonant part10. Thus, in the light emitting device100, it is possible to emit the light having the isotropic light distribution angle in the direction along the first direction direction A1and the direction along the second direction A2compared to when the length L1and the length L2are different from each other.

Further, in the light emitting device100, the distance D1between the resonant parts10a,10cand the distance D2between the resonant parts10a,10bare different from each other (e.g., the area where the plurality of resonant parts10is disposed has a substantially rectangular shape). Therefore, it is easy to increase the ratio (the length of the circumferential side to the area in an area where the plurality of resonant parts10is disposed) of the circumference of the light emitting device100compared to when the distance D1and the distance D2are equal to each other. The luminous efficiency lowers when the resonant part10is heated, but in the light emitting device100, since a substantially rectangular shape is adopted as the shape of the area where the plurality of resonant parts10is arranged, it becomes easy for the resonant part10to release the heat, and thus, high light output can be obtained.

1.2. Method of Manufacturing Light Emitting Device

Then, a method of manufacturing the light emitting device100according to the first embodiment will be described with reference to the drawings.

As shown inFIG. 3, the reflecting layer104and the buffer layer106are grown epitaxially on the substrate102in this order. As the method of achieving the epitaxial growth, there can be cited, for example, an MOCVD (Metal Organic Chemical Vapor Deposition) method and an MBE (Molecular Beam Epitaxy) method.

Then, the mask layer128is formed on the buffer layer106using the MOCVD method or the MBE method. Then, the semiconductor layer112, the light emitting layer114, and the semiconductor layer116are grown epitaxally on the buffer layer106in this order using the mask layer128as a mask. As the method of achieving the epitaxial growth, there can be cited, for example, the MOCVD method and the MBE method. Due to the present process, it is possible to form the columnar parts110. Then, the light propagation layers118are formed between the columnar parts110adjacent to each other using a spin coat method or the like. Due to the present process, it is possible to form the photonic crystal structure108.

Then, the semiconductor layer120is formed on the columnar parts110and the light propagation layers118using, for example, the MOCVD method or the MBE method.

Subsequently, the first electrode122and the second electrode124are formed using, for example, a vacuum evaporation method.

According to the process described hereinabove, it is possible to manufacture the light emitting device100.

2. Second Embodiment

2.1. Light Emitting Device

Then, a light emitting device according to a second embodiment will be described with reference to the drawings.FIG. 5andFIG. 6are each a plan view schematically showing the light emitting device200according to the second embodiment. It should be noted that inFIG. 5, the light emitting device200is illustrated in a simplified manner for the sake of convenience. Further, inFIG. 6, the illustration of members other than columnar parts110of the photonic crystal structure108is omitted. Further, inFIG. 5andFIG. 6, the first direction A1, the second direction A2, the third direction A3, and a fourth axis A4are shown as four axes crossing each other.

Hereinafter, in the light emitting device200according to the second embodiment, the members having substantially the same functions as those of the constituent members of the light emitting device100according to the first embodiment described above will be denoted by the same reference symbols, and the detailed descriptions thereof will be omitted.

In the light emitting device100described above, the columnar parts110are arranged so as to form the square lattice as shown inFIG. 2. Further, in the light emitting device100, q of the resonant parts10are arranged along the first direction A1to form the row11, and the rows11are arranged as much as r along the second direction A2perpendicular to the first direction A1.

In contrast, in the light emitting device200, a plurality of columnar parts110is arranged so as to form an equilateral-triangular lattice as shown inFIG. 6.

In the light emitting device200, the second direction A2is tilted 120° with respect to the first direction A1as shown inFIG. 5andFIG. 6. In other words, the rows11are arranged as much as r along the second direction tilted 120° with respect to the first direction A1. The fourth axis A4is tilted 60° with respect to the first direction A1. The fourth axis A4is tilted 60° with respect to the second direction A2. The third direction A3is perpendicular to a plane including the first direction A1, the second direction A2, and the fourth axis A4.

As shown inFIG. 6, a columnar part110aout of the plurality of columnar parts110is the columnar part110adjacent to a columnar part110bin a direction along an axis obtained by rotating the first direction A1clockwise as much as 30°. A columnar part110cout of the plurality of columnar parts110is the columnar part110adjacent to the columnar part110bin a direction along an axis obtained by rotating the first direction A1counterclockwise as much as 30°. A diagram formed of a straight line connecting the center of the columnar part110aand the center of the columnar part110b, a straight line connecting the center of the columnar part110band the center of the columnar part110c, and a straight line connecting the center of the columnar part110cand the center of the columnar part110ais an equilateral triangle.

In the light emitting device200, the plurality of resonant directions comprises a direction along the first direction A1, a direction along the second direction A2, and a direction along the fourth axis A4. In the resonant part10, the lengths in the direction along the first direction A1, the direction along the second direction A2, and the direction along the fourth axis A4are all equal to each other. In the plan view, for example, in the resonant part10, a distance between the center of the columnar part110located the furthest at the one side of the first direction A1and the center of the columnar part110located the furthest at the other side of the first direction A1, a distance between the center of the columnar part110located the furthest at the one side of the second direction A2and the center of the columnar part110located the furthest at the other side of the second direction A2, and a distance between the center of the columnar part110located the furthest at one side of the fourth axis A4and the center of the columnar part110located the furthest at the other side of the fourth axis A4are equal to each other. In the plan view, the shape of the resonant part10is, for example, a regular hexagon. In the plan view, a diagram formed of straight lines connecting the centers of the columnar parts110located at the outermost circumference out of the plurality of columnar parts110constituting the resonant part10is, for example, a regular hexagon.

2.2. Method of Manufacturing Light Emitting Device

Then, a method of manufacturing the light emitting device200according to the second embodiment will be described. The method of manufacturing the light emitting device200according to the second embodiment is basically the same as the method of manufacturing the light emitting device100according to the first embodiment described above. Therefore, the detailed description thereof will be omitted.

Then, a projector according to a third embodiment will be described with reference to the drawings. Firstly, a light source module provided to the projector according to the third embodiment will be described.FIG. 7is a plan view schematically showing the light source module310of the projector300according to the third embodiment.FIG. 8is a cross-sectional view along the line VIII-VIII shown inFIG. 7schematically showing the light source module310of the projector300according to the third embodiment.

As shown inFIG. 7andFIG. 8, the light source module310is provided with, for example, the light emitting devices100, a base member312, a frame member314, a lid member316, and sub-mounts318. It should be noted that inFIG. 7, the illustration of the lid member316is omitted for the sake of convenience. Further, inFIG. 7andFIG. 8, the light emitting devices100are illustrated in a simplified manner.

The base member312is, for example, a plate-like member. It is preferable for the base member312to be high in thermal conductivity. Thus, it is possible to release the heat generated in the light emitting devices100. The material of the base member312is, for example, copper, kovar (an alloy obtained by combining nickel and cobalt with iron), or aluminum nitride.

As shown inFIG. 8, the frame member314couples the base member312and the lid member316to each other. The frame member314is disposed along the outer circumference of the base member312in the plan view. It is preferable for the thermal expansion coefficient of the frame member314to be approximate to the thermal expansion coefficient of the lid member316. Thus, it is possible to reduce the stress caused in the light source module310by a difference in thermal expansion coefficient between the frame member314and the lid member316. The material of the frame member314is, for example, kovar.

The frame member314is provided with terminals315. In the illustrated example, the terminals315each penetrate the frame member314. The terminals315are electrically coupled to the light emitting devices100via interconnections not shown.

The lid member316is a sealing member for closing an opening of a recessed part defined by the base member312and the frame member314. The lid member316transmits the light emitted from the light emitting devices100. As the lid member316, there is used, for example, a sapphire substrate. The light emitting devices100are disposed in a space2formed by the base member312, the frame member314, and the lid member316. The space2can be set as a nitrogen atmosphere.

The sub-mounts318are disposed on the base member312. The sub-mounts318are respectively disposed between the base member312and the light emitting devices100. The plurality of sub-mounts318is disposed so as to correspond to the plurality of light emitting devices100.

It is preferable for the sub-mounts318to be high in thermal conductivity. Thus, it is possible to release the heat generated in the light emitting devices100. It is preferable for the thermal expansion coefficient of the sub-mounts318to be approximate to the thermal expansion coefficient of the base member312and the thermal expansion coefficient of the light emitting devices100. Thus, it is possible to reduce the stress caused in the light source module310due to a difference in thermal expansion coefficient between the sub-mounts318and the base member312, and a difference in thermal expansion coefficient between the sub-mounts318and the light emitting devices100. The material of the sub-mounts318is, for example, aluminum nitride or aluminum oxide.

The light emitting devices100are respectively disposed on the sub-mounts318. The number of the light emitting devices100disposed is, for example, more than one. In the illustrated example, the plurality of light emitting devices100is arranged in a matrix in a direction along the first direction A1and a direction along the second direction A2. A distance D3between the light emitting devices100adjacent to each other in the direction along the first direction A1and a distance D4between the light emitting devices100adjacent to each other in the direction along the second direction A2are, for example, equal to each other. It should be noted that a first distance between areas where the plurality of resonant parts10is disposed in the light emitting devices100adjacent to each other in the direction along the first direction A1can be equal to a second distance between areas where the plurality of resonant parts10is disposed in the light emitting devices100adjacent to each other in the direction along the second direction A2. Further, a third distance between substantially centers of the areas where the plurality of resonant parts10is disposed in the light emitting devices100adjacent to each other in the direction along the first direction A1can be equal to a fourth distance between substantially centers of the areas where the plurality of resonant parts10is disposed in the light emitting devices100adjacent to each other in the direction along the second direction A2. Since it is possible for the light emitting devices100to emit the light having the isotropic light distribution angle, by realizing D3=D4, it is possible to obtain illumination light having a substantially homogenous intensity distribution on an illumination target distant as much as a predetermined distance L from the light emitting devices100. Depending on a magnitude relationship between the size of the area where the plurality of resonant parts10is disposed and the distance L, it is possible to obtain the effect described above when realizing (the first distance)=(the second distance), and it is possible to obtain the effect described above when realizing (the third distance)=(the fourth distance).

Then, a configuration of the projector300will be described.FIG. 9is a diagram schematically showing the projector300according to the third embodiment.

As shown inFIG. 9, the projector300has, for example, light source modules310R,310G, and310B, diffusion elements320, first polarization plates330, second polarization plates340, light modulation elements350, a colored light combining prism360, and a projection lens370. It should be noted that inFIG. 9, the light source modules310R,310G, and310B are illustrated in a simplified manner for the sake of convenience.

The light source module310R emits red light. The light source module310G emits green light. The light source module310B emits blue light. The light source modules310R,310G, and310B are each, for example, a light source module310having the light emitting devices100. In the illustrated example, on one surface of each of the light source modules310R,310G, and310B, there is disposed a radiator fin302. The radiator fins302radiate the heat generated in the light source modules310R,310G, and310B. Thus, it is possible to suppress heating in the light source modules310R,310G, and310B to enhance the luminous efficiency.

The light emitted from the light source modules310R,310G, and310B enters the diffusion elements320, respectively. The diffusion elements320homogenize the intensity distributions of the light emitted from the light source modules310R,310G, and310B, respectively.

The light modulation elements350modulate the light emitted from the light source modules310R,310G, and310B, respectively, in accordance with image information. The light modulation elements350are, for example, transmissive liquid crystal light valves for transmitting the light emitted from the light source modules310R,310G, and310B, respectively. The projector300is an LCD (liquid crystal display) projector.

On the incident side of each of the light modulation elements350, there is disposed the first polarization plate330. The first polarization plates330adjust polarization directions and polarization degrees of the light emitted from the light source modules310R,310G, and310B, respectively. Specifically, the first polarization plates330are each an optical element for transmitting only the linearly polarized light in a specific direction. Due to the first polarization plate330, it is possible to uniform the polarization direction of the light entering the light modulation element350.

On the exit side of each of the light modulation elements350, there is disposed the second polarization plate340. The second polarization plates340function as analyzers with respect to the light emitted from the light source modules310R,310G, and310B, respectively. The light emitted from the second polarization plate340enters the colored light combining prism360.

The colored light combining prism360combines the light emitted from the light source module310R and then transmitted through the light modulation element350, the light emitted from the light source module310G and then transmitted through the light modulation element350, and the light emitted from the light source module310B and then transmitted through the light modulation element350with each other. The colored light combining prism360is, for example, a cross dichroic prism which is formed by bonding four rectangular prisms to each other, and is provided with a dielectric multilayer film for reflecting the red light and a dielectric multilayer film for reflecting the blue light disposed on the inside surfaces thereof.

The projection lens370projects the light combined by the colored light combining prism360, namely image light formed by the light modulation elements350, on a screen not shown. An enlarged image is displayed on the screen.

The projector300has the light emitting devices100which can emit the light having the isotropic light distribution angle, and is easy to release the heat, and can therefore achieve high-intensity display. Therefore, it is possible to realize a high display performance.

It should be noted that although not shown in the drawings, the projector300can be an LCoS (Liquid Crystal on Silicon) projector having reflective liquid crystal light valves for reflecting the light emitted from the light source modules310R,310G, and310B.

3.2. Modified Example of Projector

Then, a projector according to a modified example of the third embodiment will be described with reference to the drawing.FIG. 10is a diagram schematically showing the projector400according to the modified example of the third embodiment.

Hereinafter, in the projector400according to the modified example of the third embodiment, the members having substantially the same functions as those of the constituent members of the projector300according to the third embodiment described above will be denoted by the same reference symbols, and the detailed descriptions thereof will be omitted.

The projector300described above has the light source modules310R,310G, and310B as shown inFIG. 9.

In contrast, the projector400has the light source module310B, but does not have the light source modules310R,310G as shown inFIG. 10.

As shown inFIG. 10, the projector400has a light source410, a color separation optical system420, light modulation elements430R,430G, and430B, the colored light combining prism360, and the projection lens370.

The light source410has the light source module310B, a light collection optical system411, a phosphor412, a collimating optical system413, lens arrays414,415, a polarization conversion element416, and a superimposing lens417.

The light emitted from the light source module310B enters the light collection optical system411. The light collection optical system411collects the light emitted from the light source module310B. The light collection optical system411is formed of, for example, a convex lens. The light emitted from the light collection optical system411enters the phosphor412. Since the focus of the light collection optical system411is substantially set on the phosphor412, the cross-sectional shape and the intensity distribution of the light entering the phosphor412become those reflecting the light distribution angle of the light emitted from the light source module310B.

When exciting the phosphor to generate the fluorescence, the fluorescence generation efficiency is basically proportional to the intensity of the excitation light, but degrades when exceeding a predetermined intensity. Therefore, when exciting the phosphor, it is desirable to use the light having a substantially homogenous intensity distribution approximate to a top hat type not having a sharp peak in the intensity of the light.

Since the light emitted from the light emitting devices100of the light source module310B has the isotropic light distribution angle as described above, it is possible to obtain the excitation light having the intensity distribution approximate to the top hat type with, for example, the simple light collection optical system411provided with few refractive surfaces. Thus, in the projector400, it is possible to realize the high fluorescence generation efficiency, and it is possible to obtain high light output. Therefore, it is possible to realize a high-intensity projector. On the other hand, when the light emitted is not isotropic, it is necessary to use a light collection optical system provided with, for example, a number of refractive surfaces or toric surfaces, and the light collection optical system becomes complicated in some cases.

FIG. 11andFIG. 12are diagrams for explaining the intensity distribution of the light emitted from the light collection optical system411. It should be noted that inFIG. 11, there is shown the fact that the brighter a portion is, the higher the intensity of the light in that portion is. Further,FIG. 12is a cross-sectional view along the line XII-XII shown inFIG. 11. The cross-sectional surface along the XIIa-XIIa line shown inFIG. 11also has substantially the same intensity distribution as shown inFIG. 12. As shown inFIG. 11andFIG. 12, it is possible for the light emitted from the light collection optical system411to have the intensity distribution approximate to the top hat type.

FIG. 13is a diagram schematically showing the phosphor412. The phosphor412shown inFIG. 10corresponds to the cross-sectional view along the line X-X shown inFIG. 13.

As shown inFIG. 10andFIG. 13, the phosphor412is disposed on a circular disk412bwhich can be rotated by a motor412a. The phosphor412is disposed along a circumferential direction of the circular disk412b. The phosphor412is excited by the light emitted from the light collection optical system411to emit the fluorescence consisting of the red light and the green light, namely the fluorescence consisting of yellow light. The phosphor412transmits a part of the blue light emitted from the light collection optical system411. The phosphor412is, for example, a Ce:YAG (Yttrium Aluminum Garnet) type phosphor including cerium as an activator agent.

The circular disk412btransmits the blue light emitted from the light source module310B. The material of the circular disk412bis, for example, quartz glass, quartz crystal, sapphire, or resin.

As shown inFIG. 10, the collimating optical system413has a lens413afor suppressing spread of the light emitted from the phosphor412, and a lens413bfor collimating the light emitted from the lens413a, and collimates the light emitted from the phosphor412as a whole. The lenses413a,413bare each formed of a convex lens.

The lens array414has a plurality of lenses414a, the lens array415has a plurality of lenses415a, and the lenses414aand the lenses415aare set so as to correspond one-to-one to each other. The light having entered the lens array414is divided by the plurality of lenses414ainto a plurality of light beams, and then enters the corresponding lenses415aof the lens array415.

The polarization conversion element416uniforms the polarization state of the light beams emitted from the plurality of lenses415aof the lens array415to output the result as, for example, P-polarized light.

The superimposing lens417changes the proceeding directions of the plurality of light beams emitted from the polarization conversion element416to converge the plurality of light beams on the illumination target area of each of the light modulation elements430. Due to the process described above, the light emitted from the collimating optical system413is uniformed in the polarization state of the light and at the same time converted into the light having the homogenous intensity distribution on the illumination target area of each of the light modulation elements430by the lens arrays414,415, the polarization conversion element416, and the superimposing lens417.

The color separation optical system420has dichroic mirrors421,422, mirrors423,424, and425, relay lenses426,427, and field lenses428R,428G, and428B. The dichroic mirrors421,422are each formed by, for example, stacking a dielectric multilayer film on a glass surface. The dichroic mirrors421,422have a property of selectively reflecting the colored light in a predetermined wavelength band, and transmitting the colored light in the other wavelength band. Here, the dichroic mirror421reflects the green light and the blue light. The dichroic mirror422reflects the green light.

The light emitted from the superimposing lens417is white light including the red light R, the green light G, and the blue light B, and enters the dichroic mirror421.

The red light R included in the white light passes through the dichroic mirror421to enter the mirror423, and is then reflected by the mirror423to enter the field lens428R. The red light R is collimated by the field lens428R, and then enters the light modulation element430R.

The green light G included in the white light is reflected by the dichroic mirror421, and is then further reflected by the dichroic mirror422to enter the field lens428G. The green light G is collimated by the field lens428G, and then enters the light modulation element430G.

The blue light B included in the white light is reflected by the dichroic mirror421, then passes through the dichroic mirror422and the relay lens426, and is then reflected by the mirror424, and is further transmitted through the relay lens427, and then reflected by the mirror425to enter the field lens428B. The blue light B is collimated by the field lens428B, and then enters the light modulation element430B.

The light modulation elements430R,430G, and430B are each, for example, a transmissive liquid crystal light valve. The light modulation elements430R,430G, and430B are electrically coupled to a signal source such as a PC (Personal Computer) for supplying an image signal including the image information. The light modulation elements430R,430G, and430B each modulate the incident light pixel by pixel to form an image based on the image signal thus supplied. The light modulation elements430R,430G, and430B form a red image, a green image, and a blue image, respectively. The image light modulated by the light modulation elements430R,430G, and430B enters the colored light combining prism360.

In the colored light combining prism360, the three colors of image light are superimposed on each other to thereby be combined with each other, and the color image light thus combined is projected by the projection lens370on a screen440in an enlarged manner to form a color image.

In the present disclosure, some of the constituents can be omitted, or the embodiments and the modified example can be combined with each other within a range in which the features and the advantages described in the specification are provided.

The present disclosure is not limited to the embodiments described above, but can further variously be modified. For example, the present disclosure includes substantially the same configuration as the configurations described in the embodiments. Substantially the same configuration denotes a configuration substantially the same in, for example, function, way, and result, or a configuration substantially the same in object and advantage. Further, the present disclosure includes configurations obtained by replacing a non-essential part of the configuration explained in the above description of the embodiments. Further, the present disclosure includes configurations providing the same functions and the same advantages or configurations capable of achieving the same object as that of the configurations explained in the description of the embodiments. Further, the present disclosure includes configurations obtained by adding a known technology to the configuration explained in the description of the embodiments.