Optical circuit apparatus, method, and application
A new photonic integrated circuit in the form of an optical pulse-train generator utilizes a time-interleaved architecture. The circuit can generate multiple optical pulses sequentially from a single trigger pulse, with the timing and amplitude of each pulse determined by circuit design. The circuit has application in optical arbitrary waveform generation and ultrafast electro-optic modulation.
1. A time domain optical waveform generator apparatus, comprising:
a component that provides a single optical trigger pulse;
an input optical waveguide disposed to receive the single optical trigger pulse;
a plurality of coupler stages disposed along and each coupled directly to the input optical waveguide, wherein each coupler stage is characterized by a coupling coefficient that operates on the single optical trigger pulse that can be adjusted to determine an amplitude of an output optical pulse from each coupler stage;
a modulation input providing time domain digital data directly modulating in the time domain each of the coupling stages with a respective modulation signal that controls the coupling coefficient of the respective coupling stage during operation thereof on the single optical trigger pulse, said respective modulation signals not being constrained to being the same for different coupling stages;
a plurality of optical time-delay stages each one of which is disposed in the input optical waveguide, intermediate each adjacent pair of coupler stages, wherein each of the time-delay stages is characterized by an adjustable time delay that operates on the single optical trigger pulse;
an output component optically coupled to the plurality of coupler stages that optically combines the output pulses of the plurality of coupler stages into a pulse train output waveform, wherein a customized output pulse train waveform is created from a plurality of time-interleaved optical signals outputted from the plurality of coupler stages and outputted from the output component.
2. The apparatus of claim 1 , wherein the output component is an output combiner.
3. The apparatus of claim 1 , wherein the output component is an optical waveguide.
4. The apparatus of claim 1 , wherein each coupler stage is at least one optical microring resonator.
5. The apparatus of claim 4 , wherein the at least one optical microring resonator is an electro-optic modulator.
6. The apparatus of claim 5 , in which the modulation input comprises a digital data bus coupled to the at least one of the electro-optic modulators, wherein digital data to be transmitted directly modulates each microring modulator to generate a modulated, customized output pulse train waveform.
7. The apparatus of claim 4 , wherein the optical waveguides and the at least one optical microring resonator are silicon and are built on a silicon on insulator (SOI) platform.
8. The apparatus of claim 4 , wherein the at least one optical microring resonator has a racetrack configuration.
9. The apparatus of claim 4 , wherein the at least one optical microring resonator has a square configuration.
10. The apparatus of claim 4 , wherein the at least one optical microring resonator has a rectangular configuration.
11. The apparatus of claim 4 , wherein the plurality of optical microring resonators have a same resonant frequency.
12. The apparatus of claim 4 , wherein each coupler stage has a different gap distance from the input optical waveguide.
13. The apparatus of claim 1 , wherein the output combiner is one of a Y-junction and a multimode interference coupler.
14. The apparatus of claim 1 , wherein the coupling coefficients have been adjusted to provide equal power coupling of the input optical pulse into each respective coupler stage.