Spatial light modulator using phase-change matertals with improved fill factor

1. A spatial light modulator comprising:

a substrate;

a first phase change material cell on the substrate, the first phase change material cell comprising:

a first electrical heater on the substrate;

a first optical reflector layer on the first electrical heater; and

a first phase change material layer on the first optical reflector layer, wherein the first phase change material layer comprises an SbTe alloy;

wherein the first phase change material layer is substantially transparent to infrared wavelengths in an amorphous phase and is substantially opaque to infrared wavelengths in a crystalline phase; and

at least a second phase change material cell on the substrate, the second phase change material cell comprising:

a second electrical heater on the substrate;

a second optical reflector layer on the second electrical heater; and

a second phase change material layer on the second optical reflector layer, wherein the second phase change material layer comprises an SbTe alloy;

wherein the second phase change material layer is substantially transparent to infrared wavelengths in an amorphous phase and is substantially opaque to infrared wavelengths in a crystalline phase; and

a light absorber layer between the first phase change material cell and the second phase change material cell.

2. The spatial light modulator of claim 1 wherein the first phase change material layer and the second phase change material layer comprise a Ge or an In doped SbTe alloy.

3. The spatial light modulator of claim 2 wherein the first and the second phase change material layers are deposited at room temperature by sputtering.

4. The spatial light modulator of claim 1 further comprising:

an anti-reflection coating on the first and the second phase change material layer.

5. The spatial light modulator of claim 1 further comprising:

a thermal barrier between the first and the second electrical heater and the substrate.

6. The spatial light modulator of claim 5 wherein the thermal barrier comprises a dielectric or SiO 2 .

7. The spatial light modulator of claim 1 wherein the first and the second optical reflector layers are metallic.

8. The spatial light modulator of claim 1 wherein the first and the second electrical heaters comprise TiW.

9. The spatial light modulator of claim 1 :

wherein when the first phase change material layer is in an amorphous phase, light may be transmitted through the first phase change material layer; and

wherein when the first phase change material layer is in a crystalline phase, light is absorbed and not transmitted through the first phase change material layer.

10. The spatial light modulator of claim 1 :

wherein when the first phase change material or the second phase change material layer is in an amorphous phase, an optical extinction coefficient is substantially zero for wavelengths ranging from 1 to 17 micrometers; and

wherein when the first phase change material or the second phase change material layer is in a crystalline phase, the optical extinction coefficient is substantially greater than one for wavelengths ranging from 1 to 17 micrometers.

11. The spatial light modulator of claim 1 wherein the first electrical heater or the second electrical heater comprises:

a single zone heater comprising:

a first electrode and a second electrode coupled to the electrical heater; and

a heater controller coupled to the first electrode and the second electrode.

12. The spatial light modulator of claim 1 wherein the first electrical heater or the second electrical heater comprises:

a dual zone heater comprising:

a first electrode and a second electrode coupled to the electrical heater;

a second electrical heater;

a third electrode and a fourth electrode coupled to the second electrical heater; and

a heater controller coupled to the first, second, third and fourth electrode.