Optically addressed spatial light modulator (OASLM) with dielectric mirror comprising layers of amorphous hydrogenated carbon

Abstract

A reflective type liquid crystal optically addressed spatial light modulator has a first transparent substrate ( 1 b), a first transparent electrode ( 2 b) formed on the first transparent substrate ( 1 b) and a photosensitive layer ( 3 ) formed on the first transparent electrode, formed from materials including hydrogenated amorphous silicon carbide (a-Si:C:H). A read-out light-blocking layer ( 4 ) is formed on top of the photosensor layer ( 3 ) and is formed from amorphous hydrogenated carbon (a-C:H). The high reflectance dielectric multilayer mirror ( 5 ) is formed on top of the light-blocking layer ( 4 ) and can be made of alternating the a-Si:C:H layers with a higher refractive index and the a-C:H layers with lower reflective index. The modulator also has a second transparent substrate ( 1 a), a second transparent electrode ( 2 a) formed on the second transparent substrate ( 1 a), and a liquid crystal layer ( 8 ) disposed between the dielectric mirror ( 5 ) and the second transparent electrode ( 2 a). The invention allows more efficient separation of the input and read lights and increases the read light reflection, resulting in improvements to the input sensitivity, resolution, contrast ratio, and diffraction efficacy.

1. An optically addressed spatial light modulator (OASLM) comprising:
 a first transparent substrate; 
 a first transparent electrode formed on said the first transparent substrate; 
 a photoconductive layer formed on the first transparent electrode comprising hydrogenated amorphous silicon carbide; 
 a light-blocking layer formed on said the photoconductive layer and comprising hydrogenated amorphous carbon; a dielectric mirror layer, itself having a multiple layer structure formed on said the light-blocking layer; and  
 a second transparent substrate upon which is formed a second transparent electrode, and between said the second electrode and the dielectric mirror a liquid crystal layer and orientation means therefore; , wherein the light-blocking layer consists of hydrogenated amorphous carbon, and wherein the dielectric mirror is formed from alternate hydrogenated amorphous silicon carbide (a-Si:C:H) layers and hydrogenated amorphous carbon (a-C:H) layers to form layers of higher and lower refractive index respectively. 
 
     
     
       2. An The OASLM as claimed in of  claim 1  wherein the a-Si:C:H layers of the dielectric multilayer mirror have the higher refractive index in the interval from 3.7 to 3.3. 
     
     
       3. An The OASLM as claimed in of  claim 1  wherein the a-C:H layers of the dielectric multilayer mirror have the lower refractive index in the interval from 1.5 to 1.8. 
     
     
       4. An The OASLM as claimed in of  claim 1  wherein the a-C:H layers of the dielectric multilayer mirror have the lower refractive index in the interval from 1.6 to 1.7. 
     
     
       5. An The OASLM as claimed in of  claim 1  wherein the conductivities of dielectric mirror layers is in the range from 10 −9  to 10 −12  Ohm −1 cm −1 . 
     
     
       6. An The OASLM as claimed in of  claim 1  wherein the Dielectric dielectric mirror has seven layers. 
     
     
       7. An The OASLM as claimed in of  claim 1  wherein the light blocking layer has a thickness of between the limits of 0.4 μm and 0.6 μm. 
     
     
       8. An The OASLM as claimed in of  claim 1  wherein at least one of the layers of the dielectric mirror having a lower refractive index is so formed to be partially light blocking. 
     
     
       9. An The OASLM as claimed in of  claim 1  wherein the refractive index of the dielectric mirror a-Si:C:H layers is 3.5 and the refractive index of the dielectric mirror a-C:H layers is 1.6. 
     
     
       10. An optical display system incorporating an OASLM, the OASLM comprising:
 a first transparent substrate; 
 a first transparent electrode formed on said the first transparent substrate; 
 a photoconductive layer formed on the first transparent electrode, wherein the photoconductive layer comprising comprises hydrogenated amorphous silicon carbide; 
 a light-blocking layer formed on said the photoconductive layer; 
 a dielectric mirror layer, itself having a multiple layer structure formed on said the light-blocking layer; and  
 a second transparent substrate upon which is formed a second transparent electrode, and between said the second electrode and the dielectric mirror a liquid crystal layer and orientation means therefore; , wherein the light blocking layer consists of hydrogenated amorphous carbon, and wherein the dielectric mirror is formed from alternate hydrogenated amorphous silicon carbide (a-Si:C:H) layers and hydrogenated amorphous carbon (a-C:H) layers to form layers of higher and lower refractive index respectively. 
 
     
     
       11. An The optical display system as claimed in of  claim 10  wherein the display system is capable of displaying a holographic diffraction grating. 
     
     
       12. An optical signal processing system incorporating an OASLM, the OASLM comprising:
 a first transparent substrate; 
 a first transparent electrode formed on said the first transparent substrate; 
 a photoconductive layer formed on the first transparent electrode, the photoconductive layer comprising hydrogenated amorphous silicon carbide; 
 a light-blocking layer formed on said the photoconductive layer, the light-blocking layer comprising hydrogenated amorphous carbon; 
 a dielectric mirror layer, itself having a multiple layer structure formed on said the light-blocking layer; and  
 a second transparent substrate upon which is formed a second transparent electrode, and between said the second electrode and the dielectric mirror a liquid crystal layer and orientation means therefore; , wherein the light blocking layer consists of hydrogenated amorphous carbon, and wherein the dielectric mirror is formed from alternate hydrogenated amorphous silicon carbide (a-Si:C:H) layers and hydrogenated amorphous carbon (a-C:H) layers to form layers of higher and lower refractive index respectively. 
 
     
     
       13. An optically addressed spatial light modulator (OASLM) comprising:
 a first transparent substrate; 
 a first transparent electrode formed on said the first transparent substrate; 
 a photoconductive layer formed on the first transparent electrode, the photoconductive layer comprising hydrogenated amorphous silicon carbide; 
 a light-blocking layer formed on said the photoconductive layer, the light-blocking layer comprising hydrogenated amorphous carbon; 
 a dielectric mirror layer, itself having a multiple layer structure of higher and lower refractive index material so formed as to be partially light blocking; and light-blocking; and  
 a second transparent substrate upon which is formed a second transparent electrode, and between said the second electrode and the dielectric mirror a liquid crystal layer and orientation means therefore wherein the light-blocking layer includes hydrogenated amorphous carbon. 
 
     
     
       14. An optically addressed spatial light modulator (OASLM) comprising:
 means for changing an impedance in a first layer of the OASLM, wherein the first layer comprises hydrogenated amorphous silicon carbide;   means for absorbing light in a second layer of the OASLM, wherein the second layer comprises hydrogenated amorphous carbon; and   means for decoupling write and read light signals, wherein the means for decoupling comprises alternating layers of high refractive index layers and low refractive index layers, and wherein the low refractive index layers have a lower refractive index than the high refractive index layers.   
     
     
       15. The OASLM of claim 14 wherein the second layer is disposed on the first layer. 
     
     
       16. The OASLM of claim 15 wherein one or more of the alternating layers are disposed on the second layer. 
     
     
       17. The OASLM of claim 14 wherein the high refractive index layers comprise hydrogenated amorphous silicon carbide, and wherein the low refractive index layers comprise hydrogenated amorphous carbon. 
     
     
       18. The OASLM of claim 14 wherein the alternating layers comprise two or more high refractive index layers and two or more low refractive index layers. 
     
     
       19. The OASLM of claim 18 wherein the alternating layers comprise seven alternating layers. 
     
     
       20. The OASLM of claim 18 wherein the alternating layers comprise nine alternating layers. 
     
     
       21. The OASLM of claim 14 wherein one or more of the low refractive index layers are partially light-blocking. 
     
     
       22. An optically addressed spatial light modulator (OASLM) comprising:
 a photoconductive layer;   a light-blocking layer disposed on the photoconductive layer; and   a dielectric mirror disposed on the light-blocking layer, wherein the dielectric mirror includes one or more partially light-blocking layers comprising hydrogenated amorphous carbon and one or more photoconductive layers comprising hydrogenated amorphous silicon carbide.   
     
     
       23. The OASLM of claim 22 wherein the one or more partially light-blocking layers partially block light transmitted to the dielectric mirror. 
     
     
       24. The OASLM of claim 22 wherein the one or more partially light-blocking layers and the one or more photoconductive layers are alternately disposed in the dielectric mirror. 
     
     
       25. The OASLM of claim 22 wherein the one or more partially light-blocking layers have a lower refractive index than the one or more photoconductive layers. 
     
     
       26. A method of manufacturing an optically addressed spatial light modulator (OASLM) comprising:
 forming a photoconductive layer on a transparent layer;   forming a light-blocking layer on the photoconductive layer; and   forming a reflective mirror on the light-blocking layer, wherein the reflective mirror comprises alternating layers of hydrogenated amorphous carbon (a-C:H) and layers of hydrogenated amorphous silicon carbide (a-Si:C:H).   
     
     
       27. The method of claim 26 wherein the alternating layers comprise one or more layers of low refractive index and one or more layers of high refractive index. 
     
     
       28. The method of claim 27, wherein the one or more layers of low refractive index are configured to partially block light transmitted to the reflective mirror. 
     
     
       29. The method of claim 28 wherein the one or more layers of low refractive index comprise hydrogenated amorphous carbon. 
     
     
       30. The method of claim 26 wherein the a-Si:C:H layers are associated with a higher refractive index than the a-C:H layers, and wherein the light-blocking layer comprises a-C:H. 
     
     
       31. The method of claim 30 wherein the a-C:H layers are formed from at least one of methane (CH 4 ) or acetylene (C 2 H 2 ), and any hydrocarbon gas or liquid material. 
     
     
       32. The method of claim 30 wherein the a-Si:C:H layers are formed from silane (SiH 4 ), hydrogen (H 2 ), and at least one of methane (CH 4 ) or acetylene (C 2 H 2 ). 
     
     
       33. The method of claim 26 wherein the photoconductive layer is formed from a gas material comprising silane (SiH 4 ), hydrogen (H 2 ), and one or more of methane (CH 4 ) and acetylene (C 2 H 2 ). 
     
     
       34. The method of claim 26 wherein the light-blocking layer is formed from acetylene (C 2 H 2 ) and any hydrocarbon gas or liquid material. 
     
     
       35. The method of claim 26 wherein one or more of the photoconductive layer, the light-blocking layer and the reflective mirror are formed using a Chemical Vapor Deposition method. 
     
     
       36. The method of claim 35 wherein one or more of the photoconductive layer, the light-blocking layer, and the reflective mirror are formed using a Plasma Activated Chemical Vapor Deposition method. 
     
     
       37. The method of claim 35 wherein one or more of the photoconductive layer, the light-blocking layer, and the reflective mirror are formed using an Electron Spin Resonance Chemical Vapor Deposition method. 
     
     
       38. The method of claim 26 wherein the light-blocking layer comprises hydrogenated amorphous elements or alloys. 
     
     
       39. The method of claim 38 wherein the hydrogenated amorphous elements or alloys comprise one or more of the following: carbon, silicon, germanium, and tin. 
     
     
       40. The method of claim 26 wherein the photoconductive layer, the light-blocking layer, and the reflective mirror are formed in a single technological cycle. 
     
     
       41. The method of claim 40 wherein the photoconductive layer, the light-blocking layer, and the reflective mirror are formed in a single deposition chamber. 
     
     
       42. The method of claim 41 wherein the photoconductive layer, the light-blocking layer, and the reflective mirror are consecutively deposited in the single deposition chamber. 
     
     
       43. The method of claim 26 wherein the light-blocking layer comprises a-C:H. 
     
     
       44. The OASLM of claim 22 wherein the light-blocking layer comprises hydrogenated amorphous carbon.