Abstract:
The system can include one or more optical switching devices. Each optical switching device can achieve relatively high switching speeds such as between thirty (30) nano-seconds to fifty (50) nano-seconds with precise angular movement. The switching speed can be defined as the movement of an optical element from a first switching position to a second switching position. The relatively high switching speeds and precise angular movement of the optical element can be attributed to utilizing a combination of electrodes and membrane supports made from predefined materials that react to the electrodes. The optical switching device can be a microelectromechanical system (MEMS) device that can be fabricated by the adding or etching layers of materials such as in photolithography manufacturing techniques. The optical element can include a mirror made from reflective materials such as a layer of gold. The membrane supports can include planar strips fabricated from silicon based materials such as silicon nitride (Si 3 N 4 ).

Description:
STATEMENT REGARDING RELATED APPLICATIONS  
       [0001]    This application claims priority to U.S. Provisional Application No. 60/230,700, entitled, “Ultra Fast Optical Switch,” filed Sep. 7, 2000. 
     
    
     
       TECHNICAL FIELD  
         [0002]    This invention relates generally to optical networks. More particularly, the present invention relates to ultra-fast optical switches within an optical network.  
         BACKGROUND OF THE INVENTION  
         [0003]    In recent years, the exponential growth in computing power has been paralleled with an explosion in demand for communication bandwidth. One key element of this bandwidth explosion has been optical wave guides or optical fiber links, which have enabled bit rates far higher than were possible using conventional copper cables.  
           [0004]    To achieve high bit rates, optical switches are used in many conventional optical networks. Conventional switches typically rely on electronic cores, which convert optical signals to electronic signals. Electronic circuits and the switch core then direct the electronic signals to a desired output port. A final electrical-to-optical conversion is performed to transform the signal back into light for propagation of the optical signal along the optical wave guides of a network. One major problem with electronic circuits used for switching is that they do not scale well to large port counts and are costly to replace for network upgrades to support higher data rates needed for the growing demand for bandwidth.  
           [0005]    Microelectromechanical systems (MEMS) can substantially reduce or eliminate the problems associated with electronic circuits. MEMS technology comprises complex machines so small that the systems are typically measured in microns. MEMS devices typically combine electronic circuitry with mechanical structures to perform specific tasks. For optical switches, the key mechanical components are MEMS-based micro-machined mirrors fabricated on silicon chips using well established, varied-large-scale integration (VLSI) complimentary metal-oxide semiconductor (CMOS) foundry processes. These processes can include, but are not limited to, photolithography, material deposition, and chemical etching.  
           [0006]    Because of the reliability and extremely compact design of MEMS optical switching devices, these devices can be integrated easily into a variety of systems such as instrumentation and communication applications. Instrumentation applications include, but are not limited to, air bag sensors, pressure sensors, displays, adaptive optics, scanners, printers, data storage and micro-fluidics. Communication applications include, but are not limited to, packet switching, optical cross connect (OXC), optical add-drop multiplexers (OADMs), optical network protection, and optical network restoration. Specific applications for OADMs include: linear add-drop for backbone dense wave division multiplexing (DWDM) networks, hubbed rings and metro access networks, and logical mesh rings that allow dynamic path reconfiguration based on bandwidth across a network.  
           [0007]    In addition to the general MEMS optical switching device applications noted above, there are also specific MEMS optical switch device applications. For example, at least two specific MEMS optical switching designs exist today: the (a) two-dimensional (2-D) or digital approach and (b) three-dimensional (3-D) or analog approach (2N architecture). Both optical switching architectures operate on a few basic principles: an MEMS optical switch routes optical signals from one optical wave guide to another. The routing can be accomplished by steering the light, reflecting the light off a moveable mirror, and redirecting the light back into one of N possible output ports.  
           [0008]    While the operating principles of MEMS optical switching devices may appear to be simple, problems exist with conventional MEMS optical switching devices because of the need for precision control of a moveable optical element in a high speed environment. In other words, conventional MEMS optical switching devices lack precise and controlled movement of mirrors used to reflect optical signals originating from one optical wave guide and transmitted to another optical wave guide.  
           [0009]    This lack of precise and controlled movement of the optical element in a MEMS optical switching device can be attributed to the low forces that are used to move the optical element. Typically, conventional MEMS optical switches utilize electrostatic methods to induce movement of an optical element. Electrostatic methods rely on the attraction of oppositely charged mechanical elements. Conventional optical switches typically use a single electrode to pull a structure having an electrical charge of opposite sign to the electrode.  
           [0010]    Single electrode actuators do not provide for precise and controlled movement of the deflecting or moving structure. For optical switch applications in which it is desirable to merely rotate the optical element or mirror, the single electrode actuation usually produces a moment and a force. When a moment and a force is produced, translational movement of the deflecting structure is produced. This translational movement is undesirable when the optical element or mirror is designed to be simply rotated about an axis.  
           [0011]    Accordingly, there is a need in the art for an optical switching device that generates pure moments to move or rotate a respective optical element such as a mirror. A further need in the art exists for an optical switching device that can produce moments for rotating a respective optical element with increased precision and control as well as increased repeatability. Another need exists in the art for an optical switching device that can also increase the speed and precision at which optical signals are switched within an optical network. Another need exists in the art for an optical switching device that operates with uniformly low insertion loss, low operating power, and less than millisecond switching time. A further need exists in the art for an optical switching device that provides for uniform optical element positioning and registration, as well as resistance to shock and vibration. Another need exists in the art for an optical switching device that can be produced in high volumes by utilizing proven semiconductor process technology. And lastly another need exists in the art for an optical switching device that can support widely varying data rates, modulation formats, and optical signal wave lengths.  
         SUMMARY OF THE INVENTION  
         [0012]    The present invention solves the problems of conventional optical networks by providing an optical switching device that can increase the speed and precision at which optical signals are switched within an optical network. The present invention can comprise a system of one or more optical switching devices. Each optical switching device can achieve relatively high switching speeds such as between thirty (30) nano-seconds to fifty (50) nano-seconds or lower than thirty nano-second speeds with precise angular movement. The switching speed can be defined as the movement of an optical element from a first switching position to a second switching position. A switching position can be defined as a position in which electrodes are applying a voltage to maintain membrane supports and an optical element at a predefined location. The relatively high switching speeds and precise angular movement of the optical element can be attributed to utilizing a combination of electrodes and membrane supports made from predefined materials that react to the electrodes.  
           [0013]    More specifically, the optical switching device can comprise a optical element, one or more membrane supports which carry the optical element, and upper and lower electrodes that control the deflection of the one or more membrane supports. The optical switching device can comprise a microelectromechanical system (MEMS) device that can be fabricated by the adding or etching layers of materials such as in photolithography manufacturing techniques. The optical element can comprise a mirror made from reflective materials such as a layer of gold. The membrane supports can comprise planar strips fabricated from thin layered materials such as silicon nitride (Si 3 N 4 ). And the upper and lower electrodes can be electrical conductors made from materials such as titanium nitride (TiN).  
           [0014]    Because of the materials used for the membrane supports, the membrane supports can be manufactured with relatively high tensile stresses. A membrane support with high stresses can be easily stabilized and is thus suitable for supporting an optical element which is formed on a respective surface of a membrane support. Further, a membrane support with high stresses typically has increased stiffness so that it can provide rapid reaction of the optical element. The optical element typically moves in unison with the membrane support since it is usually firmly attached to the membrane support and because the membrane support has sufficient stiffness such that the optical element will not lag behind any movement of the membrane support. The stiffness of the membrane support can also reduce or prevent low modes of vibration from occurring in the optical element after moving the optical element to a switching position.  
           [0015]    In addition to providing membrane supports with high stresses, the present invention can also provide a method and system for switching optical signals that employs multiple forces, as opposed to a single force, to move the optical element into a switching position. More specifically, the present invention employs substantially pure moments to rotate the membrane supports and the optical element from a rest position to a switching direction. The substantially pure moments can be generated by activating opposing upper and lower electrodes that deflect individual membrane supports of respective pairs of membrane supports. In this way, undesirable translational movement of the membrane supports and optical element can be substantially reduced or eliminated, which, in turn, increases the precision of the angular movement of the membrane supports and optical element.  
           [0016]    According to another aspect of the present invention, a plurality of optical switching devices may be provided on a single planar surface to form a planar array of optical switching devices having multiple columns. More specifically, a plurality of optical switching devices can be aligned into an linear array. Each optical switching device of the linear array can have a unique orientation to provide a unique switching direction relative to the remaining optical switching devices within the linear array. Then, multiple linear arrays can be placed adjacent to each other, such as in columns, to form the larger planar array. The larger planar array can also be referred to as a die. Each linear array of the larger planar array or die can be assigned to a specific, individual information port. The number of information ports serviced is dependent upon the number linear arrays provided. The number of linear arrays provided, and hence the number of information ports serviced, can be in the range from thirty-two (32) to two-hundred-fifty-six (256) ports or more, depending upon the application of the planar array or die.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is a perspective view of an optical switching device according to the present invention.  
         [0018]    [0018]FIG. 2 is a side view of the optical switching device illustrated in FIG. 1.  
         [0019]    [0019]FIG. 3 is an elevational view of the optical switching device illustrated in FIG. 1.  
         [0020]    [0020]FIG. 4 is a diagram that illustrates a rest position and geometric normal of the optical element of an optical switching device when voltage is not applied to the electrodes.  
         [0021]    [0021]FIG. 5 is a diagram that illustrates an exemplary moment and switching direction or position relative to the geometric normal of the optical element of an optical switching device when moment voltage is applied to the electrodes.  
         [0022]    [0022]FIG. 6A is a diagram that illustrates exemplary lower electrodes according to the present invention.  
         [0023]    [0023]FIG. 6B is a diagram that illustrates an exemplary optical element and membrane supports according to the present invention.  
         [0024]    [0024]FIG. 6C is a diagram that illustrates exemplary optical upper electrodes according to the present invention.  
         [0025]    [0025]FIG. 7 is an exemplary cross-sectional view of the optical switching device taken along the cut line  7 - 7  of FIG. 3.  
         [0026]    [0026]FIG. 8 is a diagram illustrating an exemplary linear array of optical switching devices according to the present invention.  
         [0027]    [0027]FIG. 9 is a diagram illustrating an exemplary planar array of optical switching devices according to the present invention.  
         [0028]    [0028]FIG. 10A is a side view of an optical switching device according to another exemplary embodiment in which a standoff is disposed under the optical element.  
         [0029]    [0029]FIG. 10B is an elevational view of an optical switching device according to another exemplary embodiment in which the membrane supports are circularly shaped.  
         [0030]    [0030]FIG. 10C is an elevational view of an optical switching device according to another exemplary embodiment in which membrane supports form a cross-shape.  
         [0031]    [0031]FIG. 10D is a perspective view of an optical switching device according to another exemplary embodiment in which a spring is disposed between two membrane supports.  
         [0032]    [0032]FIG. 11 is a diagram that illustrates a rest position and geometric normal of an optical element for an optical switching device of another exemplary embodiment when voltage is not applied to a pair of electrodes.  
         [0033]    [0033]FIG. 12 is a diagram that illustrates an exemplary moment in switching direction or position relative to the geometric normal of the optical element of an optical switching device when moment voltage is applied to the pair of electrodes.  
         [0034]    [0034]FIG. 13 is a logic flow diagram illustrating a process for increasing the speed and precision at which optical signals are switched within an optical network in accordance with an exemplary embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0035]    With the present invention, ultra-fast switching of optical signals can be achieved with relative ease. That is, the optical switching device of the present invention can provide precise movement of an optical element, such as a mirror in a high speed switching environment. The optical switching device or the present invention can rotate the optical element by generating simple and pure moments. The optical switching device of the present invention can have at least two mechanically defined positions that facilitate very accurate and repeatable movement. The optical switching device of the present invention can form the building blocks for one or more linear optical switching arrays. In turn, one or more linear optical arrays can form more complex switching architectures. For example, two-dimensional switching architectures and three-dimensional switching architectures can comprise one or more of the optical linear arrays of the present invention.  
         [0036]    Referring now to the drawings, in which like numerals represent like elements throughout the several figures, aspects of the present invention and the preferred operating environment will be described.  
         [0037]    [0037]FIG. 1 illustrates an exemplary optical switching device  10  that includes electrodes  12 ,  14 ,  16 , and  18  spaced from a substrate  24 . Two electrodes  20 ,  22  are disposed adjacent to or within a substrate  24  (electrode  22  disposed within the substrate  24  is illustrated in FIG. 3 with dashed lines.) While sets of three electrodes on a side of an optical element  30  can be connected to the same side of the power supply  34 , each electrode can be controlled individually or in predetermined groupings. For example, to produce a moment or couple as will be discussed below, opposing sets of electrodes can be activated. In one exemplary embodiment, two electrodes on a same side and above a membrane support  28  such as two electrodes  14  and  18  can be activated at the same time as a diagonally opposed electrode disposed adjacent to the substrate  24  such as electrode  20 .  
         [0038]    A first membrane support  26  and a second membrane support  28  are positioned between the substrate electrodes  20 ,  22  and the other electrodes  12 ,  14 ,  16 , and  18 . The membrane supports  26 ,  28  can be connected to a side of the power supply  34  in order to close the circuit and build the electrostatic forces upon activation. The membrane supports  26 ,  28  space or separate an optical element  30  from the substrate  24 .  
         [0039]    The optical element  30  can comprise a mirror made from reflective materials such as a layer of gold. The optical element  30  can also be referred to as a micro-mirror that is of the tilting mirror variety. However, the optical element  30  is not limited to mirrors and can include other optical elements such as a lens and other like structures that manipulate optical signals. As noted above, the optical element in the micro-mirror embodiment can be made from a layer of gold. However, other reflective materials include, but are not limited to, aluminum and other like reflective coatings.  
         [0040]    Optical parameters for the exemplary micro-mirror embodiment of the present invention are listed in table 1. Table 1 summarizes the optical parameters for the micro-mirror exemplary embodiment.  
                                                   TABLE I                           Optical Parameters                Description   Dim + Tol   Remarks                                            Reflectiveness                                 99%   @ 1.55 (Gold)               Power                                 R &gt; 0.14 m                  
 
         [0041]    In this exemplary embodiment, as listed in the Table 1, the radius of curvature for the micro-mirror is ±0.1m. The reflectivity of light from the micro-mirror is preferably better than 99%. The center operational wave length of the micro-mirror is preferably 1550±20 nm. However, the present invention is not limited to these optical parameters described and listed in Table 1. Those skilled in the art will appreciate that these parameters can be adjusted for specific applications for the optical switching device  10 .  
         [0042]    The shape of the optical element  30  in one exemplary embodiment can have a substantially circular shape. However other shapes are not beyond the scope of the present invention. Other shapes include, but are not limited to, elliptical, square, rectangular, and other like shapes. The shape of the optical element  30  will often be dictated by its corresponding application. That is, the shape of the optical element  30  may be dependent upon the amount and type of optical wave guides that are feeding and receiving optical signals to and from the optical element  30 . In one exemplary embodiment where the optical element  30  is a mirror, one of the important parameters is the power of the mirror  30 . The power of the mirror  30  is typically a function of the radius of curvature of the mirror  30 . The radius of curvature can be defined by the following equation:  
       R   =         (     E   /   2     )     2       2   ×     (     Max                 deflection                 of                 the                 mirror     )                               
 
         [0043]    where R is the radius, and E is the optical power of the mirror. Also, the reflectivity value of the mirror is often a function of the cover layer and manufacturing process used to form the mirror  30 . In order to maintain high reflectivity in the infrared region (such as in the 1.55 micrometer wave length region), the mirror  30  can be formed by a definition process with very low roughness.  
         [0044]    In one exemplary embodiment, the radius of the circular mirror  30  can have a magnitude of 70 microns and a thickness of 0.5 microns. Also, in another exemplary embodiment, the amount of deflection of the optical element  30  falls preferably between minus one and plus one degrees for the respective switching directions. Optical element  30  can further include one or more tabs  32  that are designed to contact the substrate  24  after movement of the optical element  30 . The tabs  32  are designed to prevent the optical element  30  from contacting the substrate  24 .  
         [0045]    Referring now to FIG. 2, this diagram illustrates a side view of the optical switching device  10  illustrated in FIG. 1. In this diagram, the geometric shapes and relative spacings for the electrodes  12 ,  16 , (as well as the other electrodes  14 ,  18 ) can be ascertained. Also, the relative geometry of the membrane support  26  can also be ascertained. In this exemplary embodiment, the electrodes  12 ,  16  spaced from the substrate  24  have a substantially “L” shape cross-section. The membrane support  26  has a substantially “C” shape cross section. However, the present invention is not limited to these shapes illustrated in the drawings. The shape of the electrodes  12 ,  16  disposed apart from the substrate  24  are typically a function of how much light and at what angle light energy is to be received with the optical element  30 . A space or gap G exists between electrodes  12 ,  16  (and likewise electrodes  14  and  18 ) so that optical or light energy can be reflected from the surface of optical element  30  when a light source (not shown) is spaced outside the electrodes  12 ,  14 ,  16 , and  18 .  
         [0046]    The shape of the membrane support  26  can also be a function of the desired movement direction of optical element  30 . For example, referring now to FIG. 10B, the membrane support  26  can have a substantially circular shape. In another exemplary embodiment, the position of the membrane supports  26 ,  28  can form a cross shape as illustrated in FIG. 10C.  
         [0047]    Referring back to FIG. 2, the membrane supports  26 ,  28  can be disposed between respective pairs of electrodes such that substantially pure moments can be generated. Further details of the substantially pure moments generated by the present invention will be discussed in further detail with respect to FIG. 4 and FIG. 5.  
         [0048]    The membrane supports  26 ,  28  can be designed to have low inertia and high stiffness. This combination of low inertia and high stiffness properties permit the membrane supports  26 ,  28  to move to their respective switching positions in a rapid manner. In one exemplary embodiment, the membrane supports  26 ,  28  can be manufactured with high stresses within the range of 100 to 300 MegaPascals (MPa). A membrane support with high stresses typically has increased stiffness so that it can provide rapid movement of the optical element  30  disposed on the membrane support.  
         [0049]    The electrodes can be made from electrical conductors such as titanium nitride (TiN). For the electrodes  12 ,  14 ,  16 , and  18  spaced from the substrate  24 , these electrodes are spaced from the substrate  24  by portions made from silicon nitride. The substrate  24  can be made from dielectric materials such as Silicon. The membrane supports  26 ,  28  can comprise strips made from silicon nitride (Si 3 N 4 ). However, other materials are not beyond the scope of the present invention. Other materials include, but are not limited to, polysilicon, and other like materials. The materials for the membrane supports  26 ,  28  typically have a high Young&#39;s modulus such as 300 GPa, and a yield stress that is above the range of 1-2 GPa. The membrane support materials typically will comprise a dielectric material with very high breakdown voltage strength. In other words, the membrane support materials work well with high voltages.  
         [0050]    One benefit of the optical switching device  10  of the present invention is that it can be manufactured on silicon chips using well established, very-large scale integration (VLSI) complimentary metal-oxide semiconductor (CMOS) foundry processes. Further details of the manufacturing processes will be discussed below with respect to Table IV. The optical switching device  10  can be manufactured in high volume manufacturing environments and can form the basic building blocks for two-dimensional (2-D) and three-dimensional (3-D) optical switch architectures.  
         [0051]    Referring now to FIG. 3, this diagram illustrates an elevational view of the optical switching device  10  illustrated in FIG. 1. In this drawing, both pairs of the electrodes  20 ,  22  disposed within the substrate  24  are illustrated with dashed lines. The electrodes  20 ,  22  are illustrated to have a smaller surface area relative to the membrane supports  26 ,  28  which are also illustrated with dashed lines to denote these hidden views. However, the present invention is not limited to electrodes  20 ,  22  having smaller surface areas relative to the membranes supports  26 ,  28 . It is not beyond the scope of the present invention to design electrodes  20 ,  22  disposed within the substrate  24  to have surface areas larger than or substantially equal to their respective membranes supports  26 ,  28 .  
         [0052]    Also illustrated in FIG. 3 is a voltage source  34  for the electrodes. The voltage source  34  can be an electronic driver. For example, one electronic driver can comprise transistor-transistor-logic (TTL) drivers and associated electronic up converters to provide the required voltage levels for the electrodes  12 ,  14 ,  16 ,  18 ,  20 ,  22 . When multiple optical switching devices are arranged in an array, the TTL drivers can be controlled by a computer device (not shown).  
         [0053]    [0053]FIG. 4 is a diagram that illustrates a rest position and geometric normal NR of the optical element  30  of the optical switching device  10  when voltage is not applied to the electrodes  12 ,  14 ,  16 ,  18 ,  20  and  22 . It is noted that the rest position illustrated in FIG. 4 typically will not be utilized by the preferred exemplary embodiments. In the preferred exemplary embodiments, the optical element  30  will be disposed in one of two possible switching positions which will be discussed in further detail below with respect to FIG. 5.  
         [0054]    Referring now to FIG. 5, this diagram illustrates an exemplary moment M and switching direction or position relative to the geometric normal NR of the optical element  30  when a voltage is applied to predetermined electrodes. In this figure, the optical element  30  has been tilted by an angle theta (θ), where theta (θ) is defined by the geometric normal N R  when the optical element is at a rest position and by the geometrical normal N S  when the optical element is in a switching position. In FIG. 5, the z direction is magnified in order to observe the small movement of the optical element  30  and membrane supports  26 ,  28 . The optical element  30  in FIG. 5 has been rotated in a counter-clockwise direction because of the moment M produced by the two parallel forces F 26  and F 28 . A couple moment is usually defined as two parallel forces that have the same magnitude, opposite directions, and are separated by a distance. Since the resulting force of the two forces comprising the couple is zero, the only effect of the couple is to produce a rotation or tendency of rotation in a specified direction. A moment produced by a couple, called a couple moment, is equivalent to the sum of the moments of both couple forces computed about any arbitrary point in space.  
         [0055]    The force F 28  of the couple is produced when the membrane support  28  is pulled toward the electrodes  14 ,  18  because of the electrostatic force generated when a voltage is applied to electrodes  14 ,  18 . Similarly, the force F 26  of the couple is produced when the membrane support  26  is pulled towards the electrode  20  disposed within the substrate  24  when a voltage is applied to the electrode  20 . As noted above, the switching position illustrated in FIG. 5 is but one of two possible switching positions for the optical element  30 . The other switching position (not illustrated) occurs when the membrane supports  26 ,  28  are deflected in opposite directions relative to those shown in FIG. 5.  
         [0056]    The tilting angle theta (θ) illustrated in FIG. 5 is typically very small. For example, the tilting angle theta (θ) is typically within the range of 0 to 3 degrees or more. In one exemplary embodiment, the tilting angle theta can be one degree such that the two switching positions would comprise the plus one degree and minus one degree positions. With two such defined positions, accurate, repeatable, and rapid switching speeds can be achieved.  
         [0057]    Switching time for the optical switch  10  of the present invention can be defined as the time to move the optical element  30  from a first switching position (illustrated in FIG. 5) to a second switching position (not shown, but opposite to FIG. 5). The switching time of the present invention can be designed to fall within a range of 30 to 50 nanoseconds. However, the present invention is not limited to these exemplary switching times. For example, the present invention can also operate with switching times designed for microsecond switching environments.  
         [0058]    As noted above, in order to reduce the velocity of the optical element  30  when the optical element  30  reaches its switching position, an absorption mechanism or material such as tab  32  can be employed. Other absorption mechanisms for the optical element  30  can include a base with a flexible spring or some polymer which can absorb the impact energy at the end of the rotation of the optical element  30 . Also, in order to substantially reduce or prevent permanent contact between the optical element  30  and the substrate  24 , the present invention can employ dimples (not shown) on the edge of the optical element  30 .  
         [0059]    In order to substantially reduce or avoid permanent contact between the membranes supports  26 ,  28  and the substrate  24 , the present invention can also utilize anti-stiction coatings. Further, dimples (not shown) can also be disposed on the membranes supports  26 ,  28  in order to substantially reduce or eliminate permanent contact between the membranes supports  26 ,  28  and the substrate  24 .  
         [0060]    Referring now to both FIGS. 3 and 5, the forces F 26  and F 28  can be produced by applying voltages to opposing electrodes of the present invention. More specifically, to produce the forces F 26  and F 28  of FIG. 5, voltages are applied to electrodes  14 ,  18  and electrode  20 . When voltage is applied to electrodes  14 ,  18  the membrane support  28  is pulled in a direction towards electrodes  14 ,  18  which is also in a direction away from the substrate  24 . When a voltage is applied to electrode  20  disposed within the substrate  24 , the membrane support  26  is pulled towards the electrode  20  which is also a direction moving into substrate  24 . Applying voltage to these particular electrodes moves or rotates optical element  30  to a first switching position. The second switching position (not shown) can be achieved when voltage is applied to electrodes  12 ,  16  and electrode  22  disposed within the substrate  24 .  
         [0061]    In one exemplary embodiment, a bias voltage can be applied to all of the lower substrate electrodes such as lower electrodes  20 ,  22  of the present invention in order to stabilize the optical element  30  and to increase the sensitivity of the membrane supports  26 ,  28  to the voltage applied to move the membrane supports  26 ,  28 . In a further exemplary embodiment, as illustrated in FIG. 10A, a standoff  1005  can be positioned under the optical element  30 A. When the bias voltage is not applied to the lower electrodes  20 ,  22 , a separation distance can exist between the optical element  30 A and the standoff  1005  as illustrated in FIG. 10A. When a bias voltage is applied to the lower electrodes  20 ,  22 , then the optical element  30 A will contact the standoff  1005  (contact not shown in FIG. 10A). This bias voltage can be applied at all times, even when a voltage greater than the bias voltage is applied to respective pairs of upper electrodes such as upper electrodes  12 ,  16  or  14 ,  18  (not shown in FIG. 10A) and lower electrodes  20 ,  22 . By applying the bias voltage, the membrane supports  26 ,  28  and optical element  30 A are more stabilized between switching positions. Further, the movement of the supports  26 ,  28  and optical element  30 A is more controlled and less susceptible to vibration.  
         [0062]    The present invention is also not limited to the actuation or activation of electrodes discussed above. That is, other combinations of activating particular electrodes can be achieved with the present invention such that additional ranges of motion of the optical element  30  are obtained. For example, instead of activating pairs of upper electrodes, such as electrodes  14 ,  18  in unison, a single electrode such as electrode  14  could be activated to impose a different movement direction of membrane support  28  compared to the movement direction of membrane support  28  when both electrodes  14 ,  18  are activated.  
         [0063]    The present invention is not limited to electrostatic actuation of the membrane supports  26 ,  28 . Other actuation methods include piezoelectric and magnetic actuation. For the piezoelectric method, a piezo thin film can be sandwiched between two electrodes and can be placed on top of a silicon cantilever beam. When a voltage supplied across the piezoelectric film, the film can expand or contract in the lateral direction, resulting in downward or upward deflection, respectively, of the cantilever. For magnetic actuation, magnetic materials and fabrications of windings are employed. Another actuation method includes thermal micro actuation where the membrane supports  26 ,  28  can be fabricated from bimetallic or shape memory alloys (SMA). A heating resistor can be placed adjacent to the bimetallic membrane supports such that when the heating resistor is activated, metal portions of the bimetallic membrane supports  26 ,  28  will expand in response to this heating.  
         [0064]    Referring now to FIGS. 6A, 6B,  6 C, exemplary dimensions of one preferred and exemplary embodiment are illustrated. The reference letters listed in these figures correspond to Table II which lists the respective values of the dimensions in microns. The present invention is not limited to these exemplary dimensions. These dimensions are merely provided to demonstrate the micro environment in which the optical switch  10  can be employed. Although the optical switch  10  appears to have shapes that are similar to engineering structures with conventional orders of magnitude (such as feet or inches) the function of the optical switch  10  is governed by forces that do not effect traditional machines or engineering structures. The optical switch  10  is subject to atomic forces and surface science as opposed to gravity or typical inertia.  
                                           TABLE II                           Exemplary Dimensions                    Value       Dimension   Description   (microns)                    A   Bottom and top electrode widths, membrane   30           width       B   Bottom and top electrode lengths, membrane   300           length       C   Distance between electrodes   10       D   Mirror major diameter   75       E   Mirror minor diameter   70       F   Top electrode length   110       G   Bottom electrode thickness   0.1       H   Gap - bottom electrode to membrane   1.0       J   Membrane thickness   0.1       K   Gap - top electrode to membrane   1.0       L   Mirror thickness   0.5       M   Top electrode thickness   3                  
 
         [0065]    Referring now to FIG. 7, this figure illustrates an exemplary cross-sectional view of the optical switching device  10  taken along the cut line  7 - 7  of FIG. 3. This figure attempts to illustrate the relative thicknesses of materials employed by the present invention. The reference letters provided in this figure are also referenced in Table II listed above. The sizes of the structures illustrated in FIG. 7 have been drawn to illustrate the sizes of the structures relative to one another. However, the relative sizes have been exaggerated and not may be accurately depicted when comparing FIG. 7 to the values in Table II listed above.  
         [0066]    Exemplary geometrical tolerances for the components of the optical switch  10  are given below in Table III.  
                                 TABLE III                           Exemplary Tolerances            Dimension   Description   Dim + Tol [μm]   Remarks                                   Size                                 70 ± 0.5   Elliptical mirror               Thickness                                 0.5 ± 0.1   For the mirror               Roughness                                 ±20 □ nm               Position                                 ±1   x, y direction between two elements               Planar Angle                                 ±0.5 mrad   Between two elements               Tilting Angle                                 ±0.5 mrad   This is the determine by the accuracy of the studs               Length                                 ±1   For the membranes and the electrodes               Width                                 ±1   For the membranes and the electrodes                  
 
         [0067]    [0067]FIG. 8 illustrates an exemplary linear array  800  that comprises a plurality of optical switching devices  10  of the present invention. The exemplary linear array  800  can further comprise static mirrors  810  and a tuning or a folding mirror  820 . The tuning mirror  820  can be manufactured according to the same manufacturing processes for the optical switching devices  10 . In one exemplary embodiment, each static mirror  810  can comprise a reflective coating on a substrate. Further, each static mirror  810  can have an exemplary diameter of 300 microns. Each static mirror  810  can also be fabricated from thin gold layers having a thickness of 0.1 microns. The linear array  800  can also be referred to as a port. Each optical switching device  10  of the exemplary linear array or port  800  can be oriented at a different angle relative to a neighboring optical switching device  10 . In other words, the optical switching devices  10  of the exemplary linear array or port  800  are oriented at different angles relative to each other, where the angles define an amount of rotation about a center axis of respective optical elements  30 . The exemplary linear array port  800  can form the building blocks of larger, more robust planar arrays  900  as illustrated in FIG. 9.  
         [0068]    The orientation of the optical switching devices  10  of linear array  800  are typically a function of the intended switching environment. That is, the orientation of the optical switching devices  10  of linear array  800  are dependent upon the orientation of the respective optical wave guides that receive and transmit optical signals to the optical switching devices  10 . The exemplary linear array  800  can comprise six optical switching devices  10 , six static mirrors  810 , and one tuning mirror  820 . However, the present invention is not limited to this exemplary configuration. Additional or fewer optical switching devices  10 , static mirrors  810 , and tuning mirrors  820  can be employed depending upon the application of the linear array or port  800 .  
         [0069]    Referring now to FIG. 9, this diagram illustrates an exemplary planar array  900  that may be also referred to as a die. The planar array  900  includes a plurality of groupings  910  of linear arrays  800 . The planar array  900  further includes pads  920  that comprise the electrical interface between the planar array  900  and the voltage sources  34 . The pads  920  can be connected to the voltage source  34  by techniques such as wire bonding. The pads  920  can have dimensions of 120×120 microns.  
         [0070]    A number of ports or linear arrays  800  within each grouping  910  of the planar array  900  is illustrated in FIG. 9. However, the present invention is not limited to this exemplary embodiment. The number of linear arrays or ports  800  is typically a system parameter and can fall between a range of 32 to 256 ports. However, the present invention is not limited this exemplary range of ports. Additional or fewer ports are not beyond the scope of the present invention. For the planar array  900  illustrated in FIG. 9, each grouping  910  has a grouping width GW of approximately eleven (11) millimeters.  
         [0071]    As noted above, the number of linear arrays or ports  800  is usually a system parameter. The linear arrays  800  can form the building blocks for two-dimensional (2-D) or digital designs and a three-dimensional (3-D) or analog designs. The planar array  900  forms a 2-D digital approach because the optical switches  10  are arranged in a planar fashion and because the optical switches can be either of two known positions (on or off) at any given time. With this approach, the planar array  900  can be used to connect to N input fibers to N output fibers.  
         [0072]    For example, a switch matrix according to the present invention can comprise at least 40 channels-40×40 I/O. Each channel can further comprise six tilting mirrors. Port  800  can also be referred to as a channel which comprises the six tilting mirrors. Port  800  can be referred to as a switch that is capable of deflecting light to 40 different places. Each channel can comprise one switch, which may further comprise six mirrors.  
         [0073]    In the 3-D analog or beam-steering design, two arrays of N optical switches are used to connect N input to N output fibers. In this approach, each optical switch has multiple possible switching positions of at least N positions.  
         [0074]    Referring now to FIG. 10D, this diagram illustrates an optical switching device  10 D according to another exemplary embodiment. Optical switching device  10 D of FIG. 10D comprises an optical element  30 D that includes a spring  1000  disposed between the membrane supports  28 D,  26 D. Spring  1000  is designed to stabilize the movement of the optical element  30 D in a direction that is perpendicular to the tilting direction to permit for more tilting and less deflection or translational movement of the optical element  30 D.  
         [0075]    Referring now to FIGS. 11 and 12, these diagrams illustrate respective rest positions and switching directions of an optical switching device  10 E according to another exemplary embodiment. Specifically, in FIG. 11, this diagram illustrates a rest position and a geometric normal of an optical element  30 E of the optical switching device  10 E when tilting voltage is not applied to the electrodes  12 E and  20 E. In this exemplary embodiment, the optical element  30 E is supported by a single membrane support  26 E. However, the present invention is not limited to the number and sizes of the membrane supports illustrated. Additional membrane supports are not beyond the scope of the present invention.  
         [0076]    Referring now to FIG. 12, this diagram illustrates a switching position in which the optical element  30 E is tilted or rotated along its major axis. A tilting voltage is applied to both the electrodes  12 E and  20 E. The application of the tilting voltage produces forces F 12B  and F 20B  that also form a couple. The couple also generates a moment M that has an axis that coincides with the major access of the optical element  30 E. The optical element  30 E is rotated by a predetermined angle theta (θ B ). The angle theta (θ B ) is defined by the geometric normal at a rest position N R  and the geometric normal N s  of the optical element  30 E at the switching position.  
                                 TABLE IV                           Exemplary Manufacturing Steps            #   Process   DESCRIPTION   Requirements                1   Thermal Oxide   Grown on the wafer   High: 0.5 μ           Passivation       Material: SiO 2          2   LPCVD   Deposition of metal layer   High: 0.1-0.2 μm               for the lower electrodes.   Material: W        3   RIE   Etching the Metal layer to   Stopper Layer: SiO 2                 get the lower electrodes and               electronics contact pads.        4   LPCVD   Deposition base layer.   High: 0.7 μm                   Materials: Si 3 N 4          5   RIE   Etching the Si 3 N 4  to get   Stopper Layer: SiO 2 .               the standoff and the wells.        6   LPCVD   Deposition of SiO 2  layer.   High: 1.2 ± 0.05 μm                   Material: SiO 2          7   CMP   Polishing for the lower side   Flatness: 0.1 μ/               of the mirror.   100 mm        8   RIE   Etching the SiO 2  for the   Deep: 0.25 ± 0.05 μm               mirror base.   Stopper Layer: Timing                   Roughness: 10 nm        9   LPCVD   Deposition of the mirror   High: 0.5 μm               layer.   Materials: Si 3 N 4                     Roughness: 10 nm       10   RIE   Etching the Si 3 N 4  for the   Stopper Layer: SiO 2                 mirror base.       11   LPCVD   Deposition of Si 3 N 4  layer.   High: 0.1 ± 0.01 μm                   Materials: Si 3 N 4                     Roughness: 10 nm       12   RIE   Etching of the membrane.   Stopper Layer: SiO 2         13   LPCVD   Deposition of scarification   High: 1 μm               Silicon oxide layer.   Materials: SiO 2         14   RIE   Etching the SiO 2  for   Stopper Layer: Si 3 N 4                 membrane.       15   LPCVD   Deposition of Si 3 N 4  layer   High: 2 ± 0.01 μm               for the membrane bases.   Materials: Si 3 N 4         16   RIE   Etching the Si 3 N 4     Stopper Layer: SiO 2         17   RIE   Etching the SiO 2  to make a   Stopper Layer: Si 3 N 4                 connection to the               membrane.       18   Evaporation +   Deposition the membrane   High: 0.05           Liftoff   electrodes.   Material: Ti       19   LPCVD   Deposition the sacrificial   High: 0.8 +/−               layer between the mem-   0.05 μm Material:                brane and the upper   SiO 2                 electrodes.       20   RIE   Etching the SiO 2  to make a   Stopper Layer: Si 3 N 4                 connection to the Si 3 N 4                  base.       21   LPCVD   Insulation layer of the   High: 0.1               upper electrodes.   Material: Si 3 N 4         22   RIE   Etching the Upper   Stopper Layer: SiO 2                 electrodes insulation layer.       23   Evaporation +   Deposition the upper   High: 2-3 μ           Liftoff   electrodes.   Materials: Ti       24   RIE   Etching the SiO 2  for   Stopper Layer: Si 3 N 4                 the Au.       25   Evaporating +   Deposition of Cr/Ti/Au   High: 0.1 μ           Liftoff       Materials Cr/Ti/Au                   Roughness: 10 nm       26   Wet-Etching   Removing of sacrificial   Materials: SiO 2             (SAM)   materials from the device.                                                  
 
         [0077]    SAM—Self assembled monolayer which typically comprises an antistiction coating with thickness of several atoms.  
         [0078]    The present invention is not limited to the manufacturing steps listed in Table IV. Table IV merely provides one suggested technique of manufacturing the optical switching device  10  of the present invention.  
         [0079]    [0079]FIG. 13 is a logic flow diagram illustrating a process  1300  for switching optical signals. Process  1300  starts with step  1310  in which a bias voltage is applied to one or more upper or lower electrodes  12 ,  14 ,  16 ,  18 ,  20  or  22  in order to stabilize an optical element  30  and to increase sensitivity of the membrane supports  26 ,  28  to a tilting voltage. In other words, the bias voltage  10  provides for rapid deflection of the membrane supports  26 ,  28  because of the increased sensitivity of the membrane supports  26 ,  28 .  
         [0080]    In step  1320 , a desired switching direction of the optical element  30  is determined. Next, in step  1330 , a tilting voltage usually greater than the bias voltage is applied to one or more upper or lower electrodes to correspond with the switching direction. Next, in step  1340 , the membrane supports  26 ,  28  move or deflect in response to the electrostatic attraction between the membrane supports  26 ,  28  and respective activated electrodes  12 ,  14 ,  16 ,  18 ,  20  and  22  as a result of the applied tilting voltage. Equal and opposite forces generated by respective electrodes produce a moment which acts upon the membrane supports  26 ,  28  and the optical element  30 . Next in step  1350 , light energy is received at the first angle and the received light energy is reflected at a second angle theta which is defined by the switching position of the rotated optical element  30 .  
         [0081]    With the present invention, an optical switch provides at least two well-defined switching positions that allows very accurate and very repeatable movement. The present invention can achieve very fast switching times compared to other optical switches in the conventional art. Such fast switching times are critical to optical telecommunication systems.  
         [0082]    However, the present invention is not limited to optical telecommunication applications. Other applications include, but are not limited to, instrumentation applications, sensors, displays, adaptive optics, scanners, printers, data storage, microfluidics, RF applications, tunable lasers, and biomedical applications.  
         [0083]    The present invention provides an optical switching device that has uniform low insertion loss while providing nano second switching times. The present invention can operate with low voltages and is insensitive to vibration and shock. The optical switch of the present invention is of a compact design that could be manufactured with well-established, very-large-scale integration (VLSI) complementary metal-oxide semi-conductor (CMOS) foundry processes.  
         [0084]    It should be understood that the foregoing relates only to the illustrated embodiments of the present invention and that numerous changes may be made therein without departing from the spirit and scope of the invention that are defined by the following claims.