High reflectivity LCOS device

1. A spatial light modulator including:

a liquid crystal material;

a first and second electrode that provide an electric potential across said liquid crystal material to drive liquid crystals in a predetermined configuration, the first electrode comprising a grid of individually addressable pixels, each pixel being drivable at one of a number of predetermined voltage levels to provide a local phase modulation to an incident optical signal propagating at least partially in a first dimension; and

a first diffractive optical element disposed between the electrodes for at least partially reflecting the incident optical signal;

wherein the first diffractive optical element includes a first array of diffracting formations formed of a first material having a first refractive index and extending in a second dimension substantially perpendicular to the first dimension, the formations being at least partially surrounded by a second material formed of a lower refractive index; and

wherein the spatial light modulator is configured to spatially modulate a phase of the incident optical signal.

2. A spatial light modulator according to claim 1 wherein the first diffractive optical element is disposed between the liquid crystal material and the first electrode.

3. A spatial light modulator according to claim 1 wherein the first diffractive optical element is disposed within the liquid crystal material.

4. A spatial light modulator according to claim 3 wherein the first diffractive optical element also functions as an alignment layer to align the liquid crystals within the liquid crystal material.

5. A spatial light modulator according to claim 1 wherein the first material is silicon and the second material is silicon dioxide (S i O 2 ).

6. A spatial light modulator according to claim 5 wherein the thickness of the silicon material in the first dimension is in the range of 100 nm to 400 nm.

7. A spatial light modulator according to claim 6 wherein the thickness of the silicon material in the first dimension is 200 nm.

8. A spatial light modulator according to claim 6 wherein the thickness of the silicon dioxide material in the first dimension is in the range of 100 nm to 400 nm.

9. A spatial light modulator according to claim 8 wherein the thickness of the silicon dioxide material in the first dimension is 250 nm.

10. A spatial light modulator according to claim 1 wherein the diffracting formations are spaced apart in the first dimension by a fixed periodicity.

11. A spatial light modulator according to claim 1 wherein the diffracting formations are spaced apart in the first dimension by a variable periodicity.

12. A spatial light modulator according to claim 1 wherein the diffracting formations are spaced apart in the first dimension by a periodicity that is in the same order as the wavelength of the incident optical signal.

13. A spatial light modulator according to claim 12 wherein the periodicity is in the range 500 nm to 1000 nm.

14. A spatial light modulator according to claim 13 wherein the periodicity is 850 nm.

15. A spatial light modulator according to claim 14 wherein the duty cycle of the first array is 0.35.

16. A spatial light modulator according to claim 1 including a second diffractive optical element disposed between the electrodes and including a second array of diffracting formations.

17. A spatial light modulator according to claim 16 wherein at least one of the first or second diffractive optical elements is disposed within the liquid crystal material.

18. A spatial light modulator according to claim 17 wherein the first and second diffractive optical elements are disposed within the liquid crystal material.

19. A spatial light modulator according to claim 16 wherein the first and second arrays have different periodicities.

20. A spatial light modulator according to claim 16 wherein the first and second arrays have different thicknesses in the first dimension.

21. A spatial light modulator according to claim 1 wherein the first and second materials are non-metallic.

22. A method of manufacturing an optical phase modulator including:

a) providing a first electrode having a two dimensional array of individually electrically drivable cells;

b) depositing a first layer formed from a first dielectric material onto the electrode;

c) depositing a second layer formed from a second dielectric material onto the first layer;

d) etching a plurality of trenches through the second layer, the trenches extending longitudinally in a first dimension and being spaced apart in a second lateral dimension by a fixed or variable spacing;

e) depositing a third layer formed from the first dielectric material onto the second layer and into the trenches;

f) depositing a liquid crystal material over the third layer; and

g) mounting a second electrode onto the liquid crystal material.

23. A method of improving a reflectivity operation of an LCOS device the LOCS device comprising:

a liquid crystal material that controls a relative phase of orthogonal polarizations in a presence of an external electric field;

a first and second electrode that provide the external electric field across said liquid crystal material to drive liquid crystals in the liquid crystal material in a predetermined configuration, the first electrode comprising a grid of individually addressable pixels, each pixel being drivable at one of a number of predetermined voltage levels to provide a local phase modulation to an incident optical signal propagating at least partially in a first dimension; and

a reflective surface structure for reflecting light transmitted through the liquid crystal material back through the material;

the method comprising a step of:

a) depositing at least a first diffractive structure between the reflective surface structure and the liquid crystal material.

24. A method according to claim 23 further comprising the step:

b) depositing a second diffractive structure between the reflective surface and the liquid crystal material.

25. A method according to claim 24 wherein said first and second diffractive structures have different periodicity.