Passive optical diode on semiconductor substrate

1. A method of fabricating an optical device, comprising:

forming a first optical cavity formed on a semiconductor substrate, the first optical cavity configured to store light;

forming a second optical cavity on the semiconductor substrate, the second optical cavity configured to store light;

forming a first light guide on the semiconductor substrate, the first light guide having an input, the first light guide optically coupled to the first optical cavity by a first coupling strength, the first light guide optically coupled to the second optical cavity by a second coupling strength; and

forming a second light guide on the semiconductor substrate, the second light guide having an output, the second light guide coupled to the second optical cavity by a third coupling strength;

wherein the first coupling strength is greater than the second coupling strength, and the third coupling strength is greater than the second coupling strength.

2. The method of claim 1 , wherein forming the first optical cavity comprises forming a first optical resonator, and wherein forming the second optical cavity comprises forming a second optical resonator.

3. The method of claim 2 , wherein forming the first optical cavity further comprises forming the first optical resonator of single crystal silicon on an SiO 2 substrate.

4. The method of claim 3 , wherein forming the first optical resonator further comprises patterning the optical resonator using electron-beam lithography, and reactive ion-etching.

5. The method of claim 2 , wherein the first optical resonator and the second optical resonator have substantially identical resonant wavelengths for a given optical power within the cavity.

6. The method of claim 2 , wherein forming the first light guide comprises forming a first waveguide and wherein forming the second light guide comprises forming a second waveguide.

7. The method of claim 6 , wherein forming the first light guide comprises forming the first waveguide of single crystal silicon on an SiO 2 substrate.

8. The method claim 6 , wherein the first waveguide is separated from the second optical resonator by a first gap having a first gap width, the second waveguide is separated is separated from the second optical resonator by a second gap having a second gap width, and the first gap width is greater than the second gap width.

9. The method of claim 8 , wherein the first waveguide is separated from the first resonator by a third gap having a third gap width, and the first gap width is greater than the third gap width.

10. The method of claim 6 , wherein the first waveguide is separated from the second optical resonator by a first gap, the second waveguide is separated is separated from the second optical resonator by a second gap, and wherein a first refractive index of the first waveguide proximate the first gap is different from a second refractive index of the second waveguide proximate the second gap.

11. The method of claim 1 , further comprising forming a micro-heater on the semiconductor substrate such that the micro-heater is closer to the first optical cavity than to the second optical cavity.

12. The method of claim 11 , wherein forming the micro-heater further comprises evaporating titanium onto a buried oxide layer proximate the first optical resonator.

13. A method of fabricating an optical device, comprising:

forming an optical cavity on the semiconductor substrate, the optical cavity configured to store light;

forming on the semiconductor substrate a first light guide having an input, the first light guide optically coupled to the optical cavity by a first coupling strength, the first light guide having an input coupling; and

forming on the semiconductor substrate a second light guide having an output coupling, the second light guide optically coupled to the optical cavity by a second coupling strength;

wherein the second coupling strength is greater than the first coupling strength, and wherein the optical cavity, the first light guide and the second light guide are formed such that a first wavelength of light propagates from the input coupling to the output coupling with a first attenuation, and the first wavelength of light propagates from the output coupling to the input coupling with a second attenuation that is greater than the first attenuation.

14. The method of claim 13 , wherein the optical cavity comprises an optical trap.

15. The method of claim 13 , wherein the optical resonator comprises a micro-ring resonator.

16. A method of using an optical device, comprising:

receiving an optical signal at a first light guide via a first input coupling, the first light guide coupled to an optical cavity by a first coupling strength, the optical cavity disposed on a semiconductor substrate and configured to store light;

coupling the optical signal from first light guide to the optical cavity;

coupled the optical signal from the optical cavity to a second light guide, the second light guide coupled to the optical cavity by a second coupling strength, the second light guide having an output coupling;

wherein the second coupling strength is greater than the first coupling strength, and wherein the optical device is configured such that a first wavelength of light propagates from the input coupling to the output coupling with a first attention, and the first wavelength of light propagates from the output coupling to the input coupling with a second attenuation that is greater than the first attenuation.

17. The method of claim 16 , further comprising passing the received optical signal through a notch filter formed by a part of the first light guide coupled to a further optical cavity by a third coupling strength, wherein the third coupling strength is greater than the first coupling strength.

18. The method of claim 17 , wherein the optical cavity and the further optical cavity have substantially identical resonant wavelengths for a given optical power within the cavity.

19. The method of claim 17 , further comprising applying current to a micro-heater, the microheater configured to heat the further optical cavity more than the optical cavity.

20. The method of claim 17 , wherein the further optical cavity is disposed on the semiconductor substrate, and further comprising applying the received optical signal to the first light guide at a power level at which the further optical cavity heats the semiconductor substrate sufficiently to change a resonant wavelength of the further optical cavity.