Tunable optical frequency comb generator
View Patent ↗An optical device comprising a tunable optical frequency comb generator. The comb generator includes an interferometer, and an optical feed-back loop waveguide.
1. A method of use, comprising:
forming a sequence of evenly spaced optical carrier frequencies, including:
transmitting an optical carrier into an input optical coupler of an interferometer, the interferometer including:
an input optical coupler, an output optical coupler, and first and second optical waveguide arms located on a substrate, the first and second optical waveguide arms connecting respective first and second outputs of the input optical coupler to respective first and second inputs of the output optical coupler, wherein the first optical waveguide arm includes a first optical phase shifter and a first adjustable optical phase modulator, and the second optical waveguide arm includes a second adjustable optical phase modulator;
re-circulating a portion of the optical carrier through the interferometer via an optical feed-back loop waveguide, the optical feed-back loop waveguide having one end connected to a first output of the output optical coupler and having another end connected to a first input of the input optical coupler; and
driving at least one of the optical phase modulators with a periodic electrical signal.
2. The method of claim 1 , wherein driving with the periodic electrical signal includes applying a control voltage to at least one of the first adjustable optical phase modulator and the second adjustable optical phase modulator to thereby modulate the optical carrier at a radiofrequency range.
3. The method of claim 1 , further including applying a DC control current to the first optical phase shifter and applying a DC control current to the second optical phase shifter such that a center frequency of the optical carrier is suppressed by destructive interference between the optical carrier and the re-circulating portion of the optical carrier.
4. The method of claim 1 , wherein the control current applied to the first and second phase shifters include AC components that are sinusoidally driven in quadrature.
5. The method of claim 1 , further including applying a control voltage to an optical amplifier to amplify an optical power of optical sidebands that are frequency offset from a center frequency of the optical carrier.
6. The method of claim 1 , wherein the optical feed-back loop waveguide includes an optical amplifier.
7. The method of claim 1 , wherein the optical feed-back loop waveguide includes a second optical phase shifter.
8. The method of claim 1 , wherein the sequence of evenly spaced optical carrier frequencies is emitted from a second output of the output optical coupler.
9. The method of claim 1 , wherein the input optical coupler is a 2×2 optical coupler and the output optical coupler is a 2×2 optical coupler.
10. The method of claim 1 , further including an electronic controller configured for driving said at least one optical phase modulator by said periodic electrical signal.
11. The method of claim 10 , wherein the electronic controller is configured to adjust the first optical phase shifter such that an input optical carrier frequency transmitted from an input source to a second input of the input optical coupler is suppressed by destructive interference and sidebands of the optical carrier are amplified.
12. The method of claim 10 , wherein the electronic controller is configured to adjust the first optical phase shifter and second optical phase shifter such that an input optical carrier frequency transmitted from an input source to a second input of the input optical coupler is suppressed by destructive interference and sidebands of the optical carrier are amplified.
13. The method of claim 10 , wherein the electronic controller is configured to apply a forward-biased direct current to one or both of the first optical phase shifter and the second optical phase shifter.
14. The method of claim 1 , further including an electronic driver configured to apply the periodic electrical signal to the at least one of the optical phase modulators.
15. The method of claim 1 , wherein the second optical waveguide arm includes a third optical phase shifter configured to modulate an input optical carrier frequency at a radiofrequency range.
16. The method of claim 1 , wherein the optical amplifier is configured to amplify optical power of optical sidebands that are frequency offset from an input optical carrier frequency.
17. The method of claim 1 , wherein the optical amplifier includes an active layer having one or more quantum well layers sandwiched between III-V separation layers, the active layer located on the substrate including an n-doped III-V material layer, and the active layer covered by a p-doped III-V cladding layer.