CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Application No. 63/264779, entitled “OPTICALLY ADDRESSABLE LIGHT VALVES,” filed December 1, 2021. The entirety of each application referenced in this paragraph is incorporated herein by reference.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with Government support under Contract No. DE- AC52-07NA27344 awarded by the United States Department of Energy. The Government has certain rights in the invention.

BACKGROUND

Field

[0003] The present disclosure relates generally to optically addressable light valves (OALVs), and more specifically to optically addressable light valves comprising ultra- wide band gap semiconductors, specially treated photoconductors, and/or additional optical components such as reflectors, polarizers, filters or any combination thereof.

Description of the Related Art

[0004] OALVs are used to control the spatial shape and/or intensity distribution of laser beams. OALVs may comprise of a number of elements such as a photoconductor, a pair of transparent conductors (TCs), and liquid crystal. The photoconductor and liquid crystal may be sandwiched between the two transparent conductors. The OALV may be operated by applying a voltage between the two transparent conductors, through the photoconductor and liquid crystal. The conductivity of the photoconductor is controlled with a control beam of light having a first wavelength, which generates charge carriers within the photoconductor material. This light may be spatially patterned, for example, by using a digital light projection system. At locations where the photoconductor becomes conductive, the voltage dropped across the photoconductor decreases and correspondingly increases across the liquid crystal. This increase in voltage across the liquid crystal actuates the liquid crystal. At the same time, an input beam of light from a laser or other light source that is to be spatially modulated or shaped is incident on the OALV. In the locations where the liquid crystal has changed state due to the increased voltage, the liquid crystal acts to change the polarization of the input beam. The input beam from the laser or light source then passes through a polarizer, allowing only light with the correct polarization to pass through. Depending on the design, the light from the control beam may cause the liquid crystal state to be such that the light passes or is blocked. OALVs can thus be used to control the intensity across the input light beam and therefore potentially the spatial shape of the input beam in real time.

SUMMARY

[0005] The present disclosure relates generally to improvements and alternative designs for optically addressable light valves. For example, various devices, systems and methods described herein include an optically addressable light valve comprising a high optical damage threshold ultra-wide band gap (UWBG) material such as Ga2Os, AIN, BN, and diamond. In particular, in various implementations, the photoconductor and/or TCs may comprise UWBG semiconductors, which can have significantly higher laser induced damage thresholds than other designs. Use of such ultra- wide band gap semiconductors may enable higher intensity lasers.

[0006] Other devices, systems and methods described herein employ a monolithic structure that integrates the photoconductor and TC into a single element. Some optically addressable light valves described herein may use two dimensional electron or hole gas as the TC to increase the laser induced damage threshold (LIDT). Use of deep level color centers or dopants in the semiconductor photoconductor may also enable conductivity modulation with below band gap light. Some architectures describe herein allow for reflective as well as transmissive optically addressed light valve designs.

[0007] In various implementations, for example, an optically addressable light valve comprises a first transparent conductor layer, a layer of liquid crystal, and a photoconductor comprising a semiconductor having a bandgap of at least 3.5 eV. The liquid crystal is between the first transparent conductor layer and the semiconductor photoconductor. The optically addressable light valve is configured to apply a voltage across the liquid crystal and the semiconductor photoconductor.

[0008] Also disclosed herein, is an optically addressable light valve configured to spatially modulate the intensity of an input beam of light. The optically addressable light valve comprises a first transparent conductor layer, a layer of liquid crystal, and a photoconductor comprising an ultra-wide band gap semiconductor. The liquid crystal is between the first transparent conductor layer and the ultra-wide bandgap semiconductor. The optically addressable light valve is configured to apply a voltage across the liquid crystal and said ultrawide bandgap semiconductor photoconductor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

[0010] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

[0011] Figure 1 is a schematic perspective view of an example of an optically addressable light valve (OALV).

[0012] Figure 2 is a schematic cross-sectional view of an OALV comprising an ultra- wide band gap semiconductor photoconductor.

[0013] Figure 3 is a schematic cross-sectional view of an OALV comprising semiconductor photoconductor having a transparent conductive region formed therein.

[0014] Figure 4 is a schematic cross-sectional view of an OALV including a reflector configured to reflect an input beam to be patterned by said optically addressable light valve and/or the control beam configured to spatially modulate the conductivity of a photoconductor thereby spatially modulating the state of a layer of liquid crystal, which has the effect of spatially modulating the input beam.

DETAILED DESCRIPTION

[0015] As discussed above, an optically addressable light valve (OALV) 10 such as shown in Figure 1 may comprise a layer of liquid crystal 12 and a photoconductor 14 disposed between first and second transparent conductors (TCs) 16, 18. The photoconductor 14 may comprise semiconductor. The first and second transparent conductors (TCs) 16, 18 may comprise indium tin oxide (ITO). The OALV 10 may further comprise first and second alignment layers 20, 22 for aligning liquid crystal molecules adjacent thereto. A substrate 24, such as a glass substrate may provide support for the liquid crystal 12 and/or the device 10. Spacers 26 may be disposed between the substrate 24 and the photoconductor 14, and in the configuration shown in Figure 1, between the alignment layers 20, 22 to provide a space for the liquid crystal layer 12. A voltage source 28 may be electrically connected to the first and second transparent conductors 16, 18 to apply a voltage therebetween. Such a voltage is thereby applied across the layer of liquid crystal 12 and the photoconductor 14.

[0016] In various implementations, the photoconductor 14 may comprise ultrawide band gap (UWBG) semiconductor. Example UWBG semiconductor materials that may be used for the photoconductor 14 include but are not limited to Ga2Os, AIN, AlGaN, BN, diamond, Al _x Ga(2- _x )O3 where 0<x<2, Spinel gallates and aluminates such as: ZnGa2O4, MgGa2O4, ZnAhO4, and MgAhO4 or any combination thereof. Such UWBG materials can have extremely high bond strengths and critical electric fields, potentially giving them superior laser induced damage threshold (LIDT) compared to many other OALV materials. Consequently, higher peak and average power lasers and laser beams may be employed in the OALVs 10 comprising such UWBG semiconductors.

[0017] In various implementations described herein, the photoconductor 14 comprises semiconductor having a band gap of 4.0 eV, 4.1 eV, 4.2 eV, 4.3 eV, 4.4 eV, 4.5 eV,

4.6 eV, 4.7 eV, 4.8 eV, 4.9 eV, 5.0 eV, 5.1 eV, 5.2 eV, 5.3 eV, 5.4 eV, 5.5 eV, 6.0 eV, 6.1 eV, 6.2 eV, 6.3 eV, 6.4 eV, 6.5 eV, 6.6 eV, 6.7 eV, 6.8 eV, 6.9 eV, 7.0 eV or any range formed by any of these values (e.g., from 4.5 eV to 6.5 eV) although the band gap may be outside such ranges in some designs. In some implementations, for example, the photoconductor 14 comprises semiconductor having a band gap of 3.0 eV, 3.1 eV, 3.2 eV, 3.3 eV, 3.4 eV, 3.5 eV,

3.6 eV, 3.7 eV, 3.8 eV, 3.9 eV, 4.0 eV or any range formed by any of these values, although the band gap may be outside such ranges.

[0018] The OALV system 10 may further comprise a projector (not shown) configured to provide a control beam 30 comprising addressing light that is directed to and incident on the photoconductor 14. This control beam 30 may be incident on the photoconductor 14 from different sides in different designs. For example, in some configurations, the control beam 30 may be incident on the photoconductor 14 from same side as the liquid crystal layer 12 such that the control beam is transmitted through the liquid crystal layer to reach the photoconductor. In contrast, in other configurations (such as the example shown in Figure 1), the control beam 30 may be incident on the photoconductor 14 from the opposite side as the liquid crystal layer 12 such that the control beam does not need to be transmitted through the liquid crystal layer to reach the photoconductor.

[0019] In various implementations, the control beam 30 has an intensity that is spatially modulated to provide for a patterned intensity. The projector may comprise, for example, a light source to produce the control beam 30 and a spatial light modulator to modulate the intensity of the control beam at different locations across the control beam. Accordingly, the control beam 30 may have a cross-section (e.g., parallel to the x-y plane of the xyz axis depicted in Figure 1) that corresponds to a controlled intensity pattern or image 32. The variations in intensity at different locations across the cross-section of the control beam 30 (e.g., parallel to the xy plane in Figure 1) will produce variations in the conduction of the photoconductor 14 at different locations on the photoconductor where the light from the control beam is incident on the photoconductor. For example, in various implementations, the control beam 30 may have a wavelength sufficiently short and the light therefore sufficiently energetic, to excite photocarriers in the semiconductor photoconductor 14. Variation in the intensity of the control beam 30, for example, across a cross-section of the control beam orthogonal to its length, will produced a similar spatial variation in density of photocarriers in the photoconductor 14 that are generated by the control beam.

[0020] As discussed above, at locations on the photoconductor 14 where the photoconductor becomes more conductive and less resistive as a result of generation of photocarriers by the control beam 30, the voltage drop across the photoconductor decreases. The portion of the voltage applied across the layer of liquid crystal 12 by the voltage source 28 correspondingly increases with decrease in voltage across the photoconductor 14. This increase in voltage across the liquid crystal layer 12 actuates the liquid crystal, changing the state of the liquid crystal molecules at the locations of increased voltage. At the locations where the liquid crystal 12 has changed state due to the increased voltage, the liquid crystal acts to change the polarization light incident thereon. [0021] As discussed above, an input beam 34 of light to be acted on by the OALV may be directed onto the OALV 10 and the liquid crystal layer 12. This input beam 34 may originate from laser or light source (not shown in Figure 1). This input beam 34 may, in some implementations, have a particular polarization state 38, such as a vertically linearly polarized state as shown in Figure 1. This polarization state 38 may be changed by the liquid crystal layer 12 when the input light beam 34 passes through the liquid crystal layer that has be selectively activated by the change in voltage drop across the liquid crystal layer. As mentioned above, this spatial modulation in voltage drop across the liquid crystal layer 12 results when photocarriers are generated by exposing the photoconductor 14 to the control beam 30 having a spatially modulated intensity across its cross-section. The liquid crystal layer 12, may rotate or otherwise alter the polarization 38 of portions of the input beam 30 that pass through regions of the liquid crystal layer that have been activated. The amount of polarization rotation may be determined by the amount of voltage increase across the liquid crystal layer 30 at that location, which may be determined by the amount of photocarriers generated in the photoconductor 14, which may vary depending on the intensity of the control beam 30 at that location along the cross-section of the control beam orthogonal to its length.

[0022] In various implementations, the OALV 10 may include a polarizer 40 that receives the input beam 34 after being transmitted through the liquid crystal layer 12. This polarizer 40, may comprise, for example, a linear polarizer in some designs. The polarizer 40 in Figure 1 comprises a polarization beamsplitter. This polarization beamsplitter may, for example, reflect light of one polarization state such as one linear polarization state (e.g., horizontal polarization) 42 and transmit light of another polarization state such as another linear polarization state (e.g., vertical polarization) corresponding to the polarization 38 of the input beam 34. The reflected light is shown in Figure 1 as a beam 44 reflected from the polarization beamsplitter 40 and directed elsewhere. Other configurations are possible. For example, the polarization beamsplitter may reflect light of the original polarization 38 of the input beam 34 and transmit light of the other polarization state 42 such that the more the liquid crystal layer 12 changes the polarization of the input beam 34, the more light is transmitted through the polarizer 40. Still other configurations are possible.

[0023] The selective spatial modulation of the liquid crystal layer 12 by the spatially modulated control beam 30 can therefore selectively spatially modulate the input beam 34. Accordingly, the intensity of the input beam 34 across a cross-section thereof orthogonal to its length (e.g., parallel to the xy plane in Figure 1) may be altered from a first spatial intensity distribution 46 to a second spatial intensity distribution 48. This second spatial intensity distribution 48 may be therefore patterned as desired by the OALV 10. The OALV 10 thus has an output beam 50 with a spatial intensity distribution across the cross-section of the output beam orthogonal to its length (e.g., parallel to the xy plane in Figure 1) that can be controlled by the intensity distribution of the control beam 30 across the cross-section of the control beam orthogonal to its length.

[0024] Figure 2 shows a cross-sectional view of an OALV 10 wherein the photoconductor layer 14 comprises UWBG semiconductor material. As in Figure 1, the photoconductor 14 and the liquid crystal layer 12 are shown together between a pair of transparent electrodes 16, 18. First and second alignment layers 20, 22 are shown on opposite sides of the liquid crystal layer 12 while spacers 26 are shown separating the alignment layers to provide room for the liquid crystal. The various layers are included on the substrate 24 referred to in Figure 2 as an optical flat. Anti-reflective coatings ARI, AR2, AR3, AR4 are shown on various surfaces or interfaces to reduce reflection. For example, a first anti-reflective coating (ARI) is shown on the exposed surface of the second transparent electrode 18. A second anti-reflective (AR2) coating is between the photoconductor 14 and the second alignment layer 22. A third anti-reflective coating (AR3) is between the first alignment layer 20 and the first transparent electrode 16. A fourth anti-reflective (AR4) coating is formed on the optical flat 24, for example, on the exposed surface thereof.

[0025] UWBG materials can have wide band gaps, for example, greater or equal to 4.0 eV or 4.5 eV. In various implementations described herein, the UWBG photoconductor comprises a semiconductor having a band gap of 4.0 eV, 4.1 eV, 4.2 eV, 4.3 eV, 4.4 eV, 4.5 eV, 4.6 eV, 4.7 eV, 4.8 eV, 4.9 eV, 5.0 eV, 5.1 eV, 5.2 eV, 5.3 eV, 5.4 eV, 5.5 eV, 6.0 eV, 6.1 eV, 6.2 eV, 6.3 eV, 6.4 eV, 6.5 eV, 6.6 eV, 6.7 eV, 6.8 eV, 6.9 eV, 7.0 eV or any range formed by any of these values (e.g., from 4.5 eV to 5.0 eV) although the band gap may be outside such ranges in some designs. To excite carriers via band-to-band photogeneration in such ultrawide band gap semiconductors, shorter wavelengths, such as ultraviolet (UV) light may be employed. An excimer laser, mercury lamp, or other type of light source that outputs UV light may be employed as the light source for the projector in some such designs. [0026] In various implementations described herein, however, impurity doping may be employed to create deep levels or color centers in order to enable below band gap photogeneration with, e.g., visible light. Examples of such dopants include N or P in diamond, Fe or Mg in Ga2O, and O or Mg in AIN, but the dopants and semiconductor materials need not be limited to these.

[0027] Accordingly, the OALV 10 may comprise a semiconductor photoconductor 14 that includes deep level color centers or dopants such that the semiconductor photoconductor generates photocarriers in response to receiving visible light. Accordingly, such deep level color centers or dopants may have energy states deep within the band gap such that visible light can excite electrons from those deep level states nearer the conduction band than the valence band into the conduction band or holes from deep level hole states nearer the valence band than the conduction band into the valence band. This approach may advantageously reduce damage to the liquid crystal layer 12. Higher energy light such as UV light used in exciting an electron from the valence band to the conduction band of an ultra- high band gap semiconductor (or causing a hole to transition from the conduction band to the valence band) may be more likely to damage the liquid crystal than lower energy light such as visible light that can be used to cause transitions from deep level states in the band gap into the conduction band or valence band. Accordingly, in various implementations, the semiconductor photoconductor 14 includes deep level color centers or dopants that allow the control beam 30 to have a wavelength in the visible range.

[0028] In some designs, the transparent conductor 18 can be integrated with the UWBG material of the photoconductor 14. A transparent conductive region may be formed in the semiconductor surface, for example, on a side opposite the liquid crystal layer 12. The second transparent conductor layer 18 may be formed in the semiconductor photoconductor 14 on one side (e.g., the side opposite the liquid crystal) such that the second transparent conductor layer and the semiconductor photoconductor comprise a single monolithic structure 52 as illustrated in Figure 3. The conductive region can be formed in the semiconductor photoconductor 14 via impurity doping. Impurities in the semiconductor, for example, close to the surface of the semiconductor photoconductor 52 (on the side of the photoconductor opposite the liquid crystal layer 12) may create a conductive region in the semiconductor photoconductor. Accordingly, in various designs, semiconductor photoconductor 52 includes a sufficiently high amount of impurity dopants on a side of said semiconductor photoconductor opposite said liquid crystal to form a second conductive layer, the second conductive layer disposed in the semiconductor photoconductor (e.g., in, at or near the side of the semiconductor photoconductor opposite the liquid crystal layer). In various implementations, these dopants comprise shallow donor dopant to provide room temperature conductivity. These shallow level dopants in the photoconductor layer are sufficiently close in energy to the conduction band to provide significant room temperature conductivity and not need to be photo-excited to the conduction band to make the material conductive. Example of such dopants can include, Si, Sn, Ge, e.g., for Ga2O3, although the dopants should not be limited to these.

[0029] In various implementations these dopants are included throughout the depth of the photoconductive layer, although other configurations are possible.

[0030] This approach may be used regardless of whether the semiconductor photoconductor 52 is a UWBG semiconductor or not. As discussed above, the voltage source 28 may be electrically connected to this conductive region of the semiconductor photoconductor 52 and to the first transparent electrode 16 to apply a voltage across the photoconductor and the liquid crystal layer 12. As shown in Figure 3, anti-reflective coatings ARI, AR2, AR3, AR4 can be included on various surfaces or interfaces to reduce reflection. For example, a first anti-reflective coating (ARI) is shown on the exposed surface of the photoconductor 52. A second anti-reflective (AR2) coating is between the photoconductor 52 and the second alignment layer 22. A third anti-reflective coating (AR3) is between the first alignment layer 20 and the first transparent conductor 16. A fourth anti-reflective coating (AR4) is formed on the first transparent conductor 16, for example, the exposed surface thereof.

[0031] In some designs, a two-dimensional electron (or hole) gas (2DEG) can be produced in the semiconductor photoconductor 52 to create a large free electron concentration and an associated conductive region without necessarily using impurities/impurity dopants in the semiconductor photoconductor for forming the conductive region. The second transparent conductor 18 can thus be formed in the semiconductor photoconductor 52 on the side opposite the liquid crystal layer 12. The second transparent conductor layer 18 may thus be formed in the semiconductor photoconductor 52 on one side (e.g., the side opposite the liquid crystal 12) such that the second transparent conductor layer and the semiconductor photoconductor comprise a single monolithic structure 52 as illustrated in Figure 3. A variety of different materials may be employed to create the two-dimensional electron (or hole) gases in the semiconductor photoconductor 52. Such materials may comprise compound semiconductor in some implementations, and alloys thereof. In the cases, for example, materials such as AIN, CnoO,, or GaN and alloys such as AlGaN can create a large free electron concentration. Such material, may for example be disposed in a layer on the semiconductor comprising the photoconductor. In some implementations, a plurality, possibly several or many layers (e.g., AlN/GaN/AlN/GaN etc.) may be included to achieve the desired conductivity. This approach of creating a two-dimensional electron (or hole) gas may be used with UWBG semiconductor photoconductors as well as with non-UWBG material such as GaAs and GaN. Creating a conductive region in the semiconductor photoconductor 52 using two-dimensional electron (or hole) gases can potentially increase the damage threshold of these materials substantially by reducing or eliminating the large number of impurity atoms used for producing high conductivity in the semiconductor photoconductor, which may act as damage initiation sites.

[0032] The electron (or hole) gas is considered to be effectively be at the surface of the semiconductor photoconductor 52. The interface between the photoconductor semiconductor and the overlying layer would create the 2DEG, which would allow one to apply a potential at the surface of the photoconductor. As discussed above, the voltage source 28 may be electrically connected to this conductive region of the semiconductor photoconductor 52 and to the first transparent electrode to apply a voltage across the photoconductor and the liquid crystal layer. One or more anti-reflective coating such as shown in Figure 3 may also be used to reduce reflection.

[0033] Another approach to forming the transparent conductor in the semiconductor photoconductor 52 is to use a pump beam. A pump source may be located and configured to direct a pump beam onto the photoconductor 52. This pump beam may, for example, be incident on a side of the photoconductor 52 opposite of the liquid crystal layer 12. The pump source may be configured such that the pump beam has a pump wavelength sufficiently short to excite photoelectrons on a side of said semiconductor photoconductor opposite said liquid crystal. The pump wavelength may be shorter than the wavelength of the control beam 30. The control beam 30, which is used to control the bulk conductivity of photoconductor, may have a longer wavelength so as to be less absorbing than the pump beam. In contrast, the pump wavelength may be shorter such that the pump beam is more strongly absorbing so as to affect only the conductivity of the photoconductor 52 at or near the surface thereof. For example, for GaN or SiC wide band gap (WBG) semiconductors with bandgaps corresponding to wavelengths of -365 nm and 380 nm, respectively, the pump wavelength could be less than these wavelengths. For UWBG semiconductor material having band gaps >4.0 eV, band-to-band excitation have a wavelength less than roughly 310 nm. Other wavelength however can be used for other implementations.

[0034] Accordingly, in various implementations the pump source and pump beam are such that the conductive region is formed in the semiconductor photoconductor 52 at or near the surface of the photoconductor, e.g., on the side of the photoconductor opposite to the liquid crystal layer. In various implementations, for example, the wavelength of the pump beam is sufficiently short to cause the pump beam to be absorbed within a distance that is no more than *4 the thickness of semiconductor photoconductor 52. Absorption, however, will depend on energy difference between incident flux and bandgap. If shorter wavelengths are used, the distance can be reduced. Also, the absorption layer could be thicker or thinner depending on the thickness of photoconductor layer. Also depending on the design and the pump, the pump light may be fully absorbed within the photoconductive layer leaving a layer of unexcited photoconductor material adjacent to the liquid crystal. The distance, however, can vary with design. For example, the wavelength of the pump beam may be sufficiently short to cause the pump beam to be absorbed within a range of from 1 to 250 microns of the surface of the semiconductor photoconductor 52 although the distance should not be so limited.

[0035] Likewise, in various implementations, the pump source is configured and/or located such that the pump beam is incident on the semiconductor photoconductor 52 from the side of the photoconductor opposite to the liquid crystal. Similarly, the pump source may be configured and/or located such that the pump beam is not directed through the liquid crystal. The wavelength of the pump beam may, in various cases, be less than the wavelength of the input beam 34 to be patterned by the optically addressable light valve 10.

[0036] This approach of using a pump beam to form a conductive region in the semiconductor photoconductor 52, e.g., at or near the surface thereof, may be used regardless of whether the semiconductor photoconductor is a UWBG semiconductor or not. As discussed above, the voltage source 28 may be electrically connected to this conductive region of the semiconductor photoconductor 52 and to the first transparent conductor 16 to apply a voltage across the photoconductor and the liquid crystal layer 12.

[0037] Using the pump beam to provide a transparent conductive region at and/or near the surface of the semiconductor photoconductor 14 can potentially be an alternative to impurity doping, deposition of a transparent conductive oxide (TCO) such as indium tin oxide (ITO), or the use of a 2DEG as described above. Using the pump beam to provide a transparent conductive region has the potential benefit of precise control over the conductivity and the conductivity profile versus depth provide by wavelength and intensity, as well as avoiding the use of epitaxy or impurities which may introduce weak points.

[0038] Figure 4 shows another OALV design that includes a reflector 54 such as a mirror or a dichroic reflector or filter that may be employed to configure the OALV 10 to be a reflective device. The integration of a reflector 54 may allow for reflective designs in which either the control beam 30 comprising the light that changes the conductance of the photoconductor 14, 52 and/or the input beam 34 comprising the light to be patterned, is reflected rather than transmitted through the device. This configuration has the potential advantage of being able to integrate active cooling and/or a heat sink into the backside of the device.

[0039] This reflector 54 may comprise a multilayer dielectric in some implementations. This reflector 54 may, for example, comprise an interference stack, interference filter or interference coating. In some implementations, this reflector 54 comprises a dichroic filter. Dichroic filters may comprise color filters that allow for the transmission or reflection of a specific wavelength or wavelengths, while rejecting others. Dichroic filters or reflectors may selectively reflect one wavelength or wavelength range and selectively transmit another wavelength or wavelength range. The integration of dichroics into the OALV design may be advantageous as the control beam 30 comprising addressing light or the input beam 34 comprising patterned light could be selectively reflected. In some designs, for example, the dichroic filter 54 may transmit the control beam 30 but reflect the input beam 34 in certain designs. In other designs, the dichroic 54 may allow for the transmission of the input beam 34 comprising the patterned light and the reflection of the control beam 30 comprising addressing light. If the control beam 30 comprising addressing light is of high enough energy to cause damage to “downstream” optics, sending the control beam back “upstream” may be useful, e.g., if high fluences are used to generate free carriers in the photoconductive layer 14 due to low absorption. Similar designs may have advantages in being able to reflect the control beam 30 comprising addressing light back through the photoconductor conductor 14, 52, which may allow for enhanced absorption while still transmitting the input beam 34 comprising a patterned beam. Likewise, in some implementations, the control beam 30 may be incident on the OALV from the side closer to the photoconductor 14, 52 than to the liquid crystal layer 12, or vice versa. The input beam 34 may also be incident on the OALV from the side closer to the photoconductor 14, 52 than to the liquid crystal layer 12, or vice versa. In some designs, both the control beam 30 and the input beam 34 are incident on the OALV from the side closer to the photoconductor 14, 52 than to the liquid crystal layer 12. However, in other designs, both the control beam 30 and the input beam 34 are incident on the OALV 10 from the side closer to the liquid crystal 12 than to the photoconductor layer 14, 52. Other configurations are possible.

[0040] This design that incorporates a reflector 54 in the OALV 10 may be used regardless of whether the semiconductor photoconductor 14, 52 is a UWBG semiconductor or not. As discussed above, one or more anti-reflective coatings may be used to reduced reflection. Anti-reflective coatings ARI, AR2, AR3, for example, are shown on various surfaces or interfaces of the OALV device 10 of Figure 4. For example, a first anti-reflective coating (ARI) is shown on the exposed surface of the semiconductor photoconductor 52. A second anti-reflective (AR2) coating is between the first alignment layer 20 and the first transparent conductor 16. A third anti-reflective coating (AR3) is formed on the first transparent conductor 16, for example, the exposed surface thereof.

[0041] As discussed above, the OALV 10 may include a polarizer 40 such as a polarization beamsplitter. The OALV 10, for example, may operate by inducing a polarization shift in the input beam 34, which in then filtered using a downstream polarizer 40. Various designs may integrate this polarizer 40 into the OALV device 10. For example, the polarizer 40 may be included in a stack with any one or more of the other elements such as the photoconductor 14, 52, the layer of liquid crystal 12, the alignment layers 20, 22, the first transparent conductor 16. In some implementations, the polarizer 40 may comprise a multilayer dielectric. Advantages to such an approach could include compactness of the system and/or reduced system-level complexity (e.g., reducing the need to align and clean additional free-space optics). This design that incorporates the polarizer 40 with the stack of elements that form the OALV device 10 may be used regardless of whether the semiconductor photoconductor 14, 52 is a UWBG semiconductor or not.

[0042] A wide variety of variations in the OALV device or system design and method of use are possible. Any of the features described herein can be combined with any other features described herein. Other variations are possible.

Examples:

[0043] This disclosure provides various examples of devices, systems, and methods. Some such examples include but are not limited to the following examples.

Part I:

1. An optically addressable light valve configured to spatially modulate the intensity of an input beam of light, the optically addressable light valve comprising: a first transparent conductor layer; a layer of liquid crystal; and a photoconductor comprising a semiconductor having a bandgap of at least 3.5 eV, said liquid crystal between said first transparent conductor layer and said semiconductor photoconductor, wherein said optically addressable light valve is configured to apply a voltage across said liquid crystal and said semiconductor photoconductor.

2. The optically addressable light valve of Example 1, wherein said semiconductor photoconductor has a bandgap of at least 4.0 eV.

3. The optically addressable light valve of any of the examples above, wherein said semiconductor photoconductor has a bandgap of at least 4.5 eV.

4. The optically addressable light valve of any of the examples above, wherein said semiconductor photoconductor comprises an ultra-wide bandgap semiconductor.

5. The optically addressable light valve of any of the examples above, wherein said semiconductor photoconductor comprises one or more of CnoO,, AIN, BN, diamond, AlxGap- _X )O3 where 0<x<2, or spinel gallates and aluminates such as: ZnGa2O4, MgGa2O4, ZnAhO4, and MgAhO4. 6. The optically addressable light valve of any of the examples above, wherein said semiconductor photoconductor includes deep level color centers or dopants such that the semiconductor photoconductor generates photocarriers in response to receiving visible light.

7. The optically addressable light valve of Example 6, wherein said semiconductor photoconductor comprises diamond and said deep level color centers or dopants comprise P or N, wherein said semiconductor photoconductor comprises Ga2Os and said deep level color centers or dopants comprise Sn, Fe or Mg, or wherein said semiconductor photoconductor comprises AIN and said deep level color centers or dopants comprise O or Mg.

8. The optically addressable light valve of any of the examples above, further comprising a second transparent conductor layer, said liquid crystal and said semiconductor photoconductor between said first and second transparent conductor layers, said optically addressable light valve being configured to apply a voltage between said first and second conductor layers.

9. The optically addressable light valve of any of Examples 1-7, wherein a second transparent conductor layer is formed in said semiconductor photoconductor on one side such that said second transparent conductor layer and said semiconductor photoconductor comprise a single monolithic structure.

10. The optically addressable light valve of Claim 8, wherein said second transparent conductor layer comprises Ga2Os, AIN, BN, or diamond.

11. The optically addressable light valve of any of the Examples 1-7 and 9-10, wherein said semiconductor photoconductor includes a sufficiently high amount of impurity dopants on a side of said semiconductor opposite said liquid crystal to form a second conductive layer, said second conductive layer disposed in said semiconductor photoconductor.

12. The optically addressable light valve of any of Examples 1-7 and 9-11, wherein said semiconductor photoconductor includes at least one layer of material to form a two- dimensional electron or hole gas on a side of said semiconductor photoconductor opposite said liquid crystal, said two-dimensional electron or hole gas disposed in said semiconductor photoconductor.

13. The optically addressable light valve of Example 12, wherein said at least one layer of material configured to form a two-dimensional electron or hole gas comprises a layer of aluminum nitride (AIN) or layer of gallium nitride (GaN) or a combination of layers of AIN and GaN.

14. The optically addressable light valve of Example 12, wherein said semiconductor photoconductor comprises Ga2Oa and said at least one layer of material configured to form a two-dimensional electron or hole gas comprises a layer of aluminum gallium oxide (AlGaO) thereby forming a two-dimensional electron gas at the interface of the Ga2Oa and the AlGaO.

15. An optically addressable light valve configured to spatially modulate the intensity of an input beam of light, said optically addressable light valve comprising: a first transparent conductor layer; a layer of liquid crystal; and a photoconductor comprising an ultra-wide band gap semiconductor, said liquid crystal between said first transparent conductor layer and said ultra-wide bandgap semiconductor, wherein said optically addressable light valve is configured to apply a voltage across said liquid crystal and said ultra-wide bandgap semiconductor photoconductor.

16. The optically addressable light valve of Example 15, wherein said semiconductor photoconductor has a bandgap of at least 4.5 eV.

17. The optically addressable light valve of any of Examples 15 or 16, wherein said semiconductor photoconductor comprises one or more of Ga2Os, AIN, BN, diamond, Al _x Ga ₍ 2- _X )O3 where 0<x<2, or spinel gallates and aluminates such as: ZnGa2O4, MgGa2O4, ZnAhO4, and MgAhO4.

18. The optically addressable light valve of any of Examples 15-17, wherein said semiconductor photoconductor includes deep level color centers or dopants such that the semiconductor photoconductor generates photocarriers in response to receiving visible light.

19. The optically addressable light valve of Example 18, wherein said semiconductor photoconductor comprises diamond and said deep level color centers or dopants comprise P or N, wherein said semiconductor photoconductor comprises Ga2Oa and said deep level color centers or dopants comprise Sn, Fe or Mg, or wherein said semiconductor photoconductor comprises AIN and said deep level color centers or dopants comprise O or Mg.

20. The optically addressable light valve of any of Examples 15-19, further comprising a second transparent conductor layer, said liquid crystal and said semiconductor photoconductor between said first and second transparent conductor layers, said optically addressable light valve being configured to apply a voltage between said first and second conductor layers.

21. The optically addressable light valve of any of Examples 15-19, wherein a second transparent conductor layer is formed in said semiconductor photoconductor on one side such that said second transparent conductor layer and said semiconductor photoconductor comprise a single monolithic structure.

22. The optically addressable light valve of any of Examples 15-19 and 21, wherein a second transparent conductor layer comprises one or more of Ga2Os, AIN, BN, diamond, Al _x Ga(2 x)O3 where 0<x<2, or spinel gallates and aluminates such as: ZnGa2O4, MgGa2O4, ZnAhO4, and MgAhO4.

23. The optically addressable light valve of any of Examples 15-19 and 22, wherein said semiconductor photoconductor includes a sufficiently high amount of impurity dopants on a side of said ultra-wide bandgap semiconductor opposite said liquid crystal to form a second conductive layer, said second conductive layer disposed in said semiconductor photoconductor.

24. The optically addressable light valve of any of Examples 15-19 and 23, wherein said semiconductor photoconductor includes at least one layer of material to form a two- dimensional electron or hole gas on a side of said semiconductor photoconductor opposite said liquid crystal, said two-dimensional electron or hole gas disposed in said semiconductor photoconductor.

25. The optically addressable light valve of Example 24, wherein said at least one layer of material configured to form a two-dimensional electron or hole gas comprises a layer of aluminum nitride (AIN) or layer of gallium nitride (GaN) or a combination of layers of AIN and GaN.

26. The optically addressable light valve of Example 24, wherein said semiconductor photoconductor comprises Ga2Oa and said at least one layer of material configured to form a two-dimensional electron or hole gas comprises a layer of aluminum gallium oxide (AlGaO) thereby forming a two-dimensional electron gas at the interface of the Ga2Oa and the AlGaO. Part II:

1. An optically addressable light valve configured to spatially modulate the intensity of an input beam of light, said optically addressable light valve comprising: a first transparent conductor layer; a layer of liquid crystal; and a semiconductor photoconductor, said layer of liquid crystal between said first transparent conductor layer and said semiconductor photoconductor, said semiconductor photoconductor including impurity dopants on a side of said semiconductor photoconductor opposite said layer of liquid crystal to form a second conductor layer, said second conductor layer disposed in said semiconductor photoconductor, wherein said optically addressable light valve is configured to apply a voltage across said liquid crystal and said semiconductor photoconductor.

2. The optically addressable light valve of Example 1, the voltage may be applied across the first and second transparent conductor.

3. An optically addressable light valve configured to spatially modulate the intensity of an input beam of light, said optically addressable light valve comprising: a first transparent conductor layer; a layer of liquid crystal; and a semiconductor photoconductor, said layer of liquid crystal between said first transparent conductor layer and said semiconductor photoconductor, said semiconductor photoconductor including a second conductor layer formed in said semiconductor photoconductor to provide a single monolithic structure comprising said second conductor layer and said semiconductor photoconductor, wherein said optically addressable light valve is configured to apply a voltage across said liquid crystal and said semiconductor photoconductor.

4. The optically addressable light valve of Example 3, the voltage may be applied across the first and second transparent conductor.

Part III:

1. An optically addressable light valve configured to spatially modulate the intensity of an input beam of light, said optically addressable light valve comprising: a first transparent conductor layer; a layer of liquid crystal; and a semiconductor photoconductor, said layer of liquid crystal between said first transparent conductor layer and said semiconductor photoconductor, said semiconductor photoconductor including a two-dimensional electron or hole gas on a side of said semiconductor photoconductor opposite said liquid crystal to form a second conductive layer, said second conductive layer disposed in said semiconductor photoconductor, wherein said optically addressable light valve is configured to apply a voltage across said liquid crystal and said semiconductor photoconductor.

2. The optically addressable light valve of Example 1, further comprising at least one layer of material to form said two-dimensional electron or hole gas on a side of said semiconductor photoconductor opposite said liquid crystal.

3. The optically addressable light valve of Example 2, wherein said at least one layer of material configured to form said two-dimensional electron or hole gas comprises a layer of aluminum nitride (AIN) or layer of gallium nitride (GaN) or a combination of layers of AIN and GaN.

4. The optically addressable light valve of Example 2 or 3, wherein said at least one layer of material configured to form said two-dimensional electron or hole gas comprises a compound nitrides.

5. The optically addressable light valve of Example 2, wherein said semiconductor photoconductor comprises Ga2Oa and said at least one layer of material configured to form said two-dimensional electron or hole gas comprises a layer of aluminum gallium oxide (AlGaO).

6. An optically addressable light valve configured to spatially modulate the intensity of an input beam of light, said optically addressable light valve comprising: a first transparent conductor layer; a layer of liquid crystal; and a semiconductor photoconductor, said layer of liquid crystal between said first transparent conductor layer and said semiconductor photoconductor; and at least one layer of material on a side of said semiconductor photoconductor opposite said layer of liquid crystal configured to form a two-dimensional electron or hole gas to provide a second conductor layer in said semiconductor photoconductor, wherein said optically addressable light valve is configured to apply a voltage across said liquid crystal and said semiconductor photoconductor.

7. The optically addressable light valve of Example 6, wherein said at least one layer of material configured to form said two-dimensional electron or hole gas comprises a layer of aluminum nitride (AIN) or layer of gallium nitride (GaN) or a combination of layers of AIN and GaN.

8. The optically addressable light valve of Example 6 or 7, wherein said at least one layer of material configured to form said two-dimensional electron or hole gas comprises a compound nitrides.

9. The optically addressable light valve of Example 6, wherein said semiconductor photoconductor comprises Ga2Oa and said at least one layer of material configured to form said two-dimensional electron or hole gas comprises a layer of aluminum gallium oxide (AlGaO).

Part IV:

1. An optically addressable light valve configured to spatially modulate the intensity of an input beam of light, said optically addressable light valve comprising: a first transparent conductor layer; a layer of liquid crystal; a photoconductor comprising a semiconductor, said liquid crystal between said first transparent conductor layer and said semiconductor photoconductor; and a reflector, wherein said optically addressable light valve is configured to apply a voltage across said liquid crystal and said semiconductor photoconductor.

2. The optically addressable light valve of Example 1, wherein said reflector comprises a dielectric mirror.

3. The optically addressable light valve of any of the example above, wherein said reflector comprises a multilayer. 4. The optically addressable light valve of Example 3, wherein said multilayer comprises an optical interference stack.

5. The optically addressable light valve of any of the example above, wherein said reflector is on the same side of said layer of liquid crystal as said semiconductor photoconductor.

6. The optically addressable light valve of any of the example above, wherein said reflector is between said semiconductor photoconductor and said layer of liquid crystal.

7. The optically addressable light valve of any of the examples above, further comprising a projector configured to provide a control beam having a wavelength sufficiently short to excite photocarriers in said semiconductor photoconductor.

8. The optically addressable light valve of Example 7, wherein said control beam is directed through said liquid crystal to said semiconductor photoconductor.

9. The optically addressable light valve of Example 7 or 8, wherein said reflector is configured to transmit said wavelength of said control beam.

10. The optically addressable light valve of any of the examples above, wherein said reflector is configured to reflect the input beam to be patterned by said optically addressable light valve.

11. The optically addressable light valve of any of the examples above, further comprising a heat sink and/or cooling device, said reflector disposed between said heat sink and/or cooling devices and said liquid crystal.

12. The optically addressable light valve of any of the examples above, further comprising a heat sink and/or cooling device on a side of said reflector opposite said liquid crystal.

13. The optically addressable light valve of any of the examples above, further comprising a heat sink and/or cooling device on a side of said semiconductor photoconductor opposite said liquid crystal.

14. The optically addressable light valve of any of the examples above, wherein said reflector is configured to reflect the input beam to be patterned by said optically addressable light valve such that said input beam is not incident on said semiconductor photoconductor.

15. The optically addressable light valve of any of the examples above, wherein said semiconductor photoconductor comprise ultra- wide band gap semiconductor. Part V:

1. An optically addressable light valve configured to spatially modulate the intensity of an input beam of light, said optically addressable light valve comprising: a first transparent conductor layer; a layer of liquid crystal; a photoconductor comprising a semiconductor, said liquid crystal between said first transparent conductor layer and said semiconductor photoconductor; and a pump source configured to provide a pump beam having a pump wavelength sufficiently short to excite photoelectrons on a side of said semiconductor photoconductor opposite said liquid crystal, wherein said optically addressable light valve is configured to apply a voltage across said liquid crystal and said semiconductor photoconductor.

2. The optically addressable light valve of Example 1 above, wherein said wavelength is sufficiently short to cause said pump beam to be absorbed within a distance that is no more than *4 the thickness of said semiconductor photoconductor.

3. The optically addressable light valve of any of the examples above, wherein said wavelength is sufficiently short to cause said pump beam to be absorbed within a 1 to 250 microns of said semiconductor photoconductor.

4. The optically addressable light valve of any of the examples above, wherein said pump source is configured such that said pump beam is incident on said semiconductor photoconductor from the side of said semiconductor photoconductor opposite to said liquid crystal.

5. The optically addressable light valve of any of the examples above, wherein said pump source is configured such that said pump beam is not directed through said liquid crystal.

6. The optically addressable light valve of any of the examples above, wherein said wavelength of said pump beam is less than the wavelength of said input beam to be patterned by said optically addressable light valve.

7. The optically addressable light valve of any of the examples above, wherein said semiconductor photoconductor comprise ultra- wide band gap semiconductor. Part VI:

1. An optically addressable light valve configured to spatially modulate the intensity of an input beam of light, said optically addressable light valve comprising: a first transparent conductor layer; a layer of liquid crystal; a photoconductor comprising a semiconductor, said liquid crystal between said first transparent conductor layer and said semiconductor photoconductor; and a polarizer integrated in a stack with said first transparent conductor layer, said semiconductor photoconductor, or said layer of liquid crystal or any combination thereof, wherein said optically addressable light valve is configured to apply a voltage across said liquid crystal and said semiconductor photoconductor.

2. The optically addressable light valve of Example 1, wherein said polarizer is integrated in a stack with said semiconductor photoconductor and said layer of liquid crystal.

3. The optically addressable light valve of any of the examples above, wherein said polarizer is integrated in a stack with said first transparent conductor layer and said layer of liquid crystal.

4. The optically addressable light valve of any of the examples above, wherein said polarizer is integrated in a stack with said first transparent conductor layer, said semiconductor photoconductor, and said layer of liquid crystal.

5. The optically addressable light valve of any of the examples above, wherein said polarizer comprises a multilayer.

6. The optically addressable light valve of any of the examples above, wherein said polarizer comprises a multilayer dielectric comprising multiple dielectric layers.

7. The optically addressable light valve of Example 5, wherein said multilayer comprises an optical interference stack.

8. The optically addressable light valve of any of the examples above, wherein said semiconductor photoconductor comprise ultra- wide band gap semiconductor. [0046] Although the description above contains many details and specifics, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Other implementations, enhancements and variations can be made based on what is described and illustrated in this patent document. The features of the embodiments described herein may be combined in all possible combinations of methods, apparatus, modules, systems, and computer program products. Certain features that are described in this patent document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments.

[0047] Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art. In the claims, reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more." All structural and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element or component in the present disclosure is intended to be dedicated to the public regardless of whether the element or component is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112, sixth paragraph, unless the element is expressly recited using the phrase "means for."