Integrated broadband optical isolator
View Patent ↗An integrated broadband optical isolator that operates over a wide bandwidth, wherein the optical isolator comprises sinusoidally driven phase modulators inside an interferometer. In one exemplary embodiment the optical isolator comprises: a 1×N input optical coupler, where N>2; a N×1 output optical coupler; N optical waveguides optically connecting the 1×N input optical coupler to the N×1 output optical coupler, each one of the N optical waveguides including two phase modulators, wherein each of the phase modulators are driven at a frequency f and wherein the time it takes an optical signal to travel from the center of one phase modulator in a particular waveguide to the center of the other phase modulator in that particular waveguide is substantially equal to 1/4f.
1. An apparatus comprising:
an optical isolator comprising:
a 1×N input optical coupler;
a N×1 output optical coupler; and
N optical waveguides optically connecting the 1×N input optical coupler to the N×1 output optical coupler, N being greater than two,
wherein each of at least three of the N optical waveguides includes at least two phase modulators.
2. The apparatus according to claim 1 wherein optical phases of light traversing the N optical waveguides are adjusted to be in phase.
3. The apparatus according to claim 2 wherein radio frequency phases are adjusted to be substantially equally distributed across 360 degrees.
4. The apparatus according to claim 1 wherein N=4.
5. The apparatus according to claim 1 wherein N=6.
6. The apparatus according to claim 1 wherein the 1×N input optical coupler and/or the N×1 output optical coupler is a multimode interference coupler.
7. The apparatus according to claim 1 wherein the 1×N input optical coupler and/or the N×1 output optical coupler is a star coupler.
8. The apparatus according to claim 1 wherein the N optical waveguides are silicon waveguides.
9. The apparatus according to claim 1 wherein the at least two phase modulators are depletion modulators in silicon.
10. The apparatus according to claim 1 wherein the at least two phase modulators are carrier injection modulators in silicon.
11. The apparatus according to claim 1 wherein N=4 such that four optical waveguides N[1], N[2], N[3], and N[4] optically connect the input optical coupler to the output optical coupler, wherein each of the four optical waveguides include two phase modulators M[N,1] and M[N,2] where N is the optical waveguide number, wherein the individual phase modulators are driven according to the following:
Phase
Phase
Waveguide
Modulator 1
Modulator 2
N = 1
Acos(2π ft)
Asin(2π ft)
N = 2
Acos(2π ft)
Asin(2π ft)
N = 3
Asin(2π ft)
Acos(2π ft)
N = 4
Asin(2π ft)
Acos(2π ft).
12. The apparatus of claim 11 wherein the at least two phase modulators are arranged to be driven as four pairs of push pull modulators, driven with a total of four drives.
13. The apparatus of claim 11 wherein each of the four optical waveguides acts as a narrow-band isolator such that a signal propagating in a forward direction exhibits no effect while in a backward direction destructive interference is exhibited for generated backward propagating wavelengths.
14. The apparatus of claim 13 , wherein the N optical waveguides are of substantially equal length.
15. The apparatus of claim 1 , wherein the N optical waveguides are of substantially equal length.
16. An apparatus, comprising:
a 1×N input optical coupler;
a N×1 output optical coupler; and
N optical waveguides optically connecting the 1×N input optical coupler to the N×1 output optical coupler, the N optical waveguides including a first optical waveguide and a second optical waveguide,
wherein the first optical waveguide comprises a first phase modulator configured to be driven at a first phase and a second phase modulator configured to be driven at a second phase,
wherein the second optical waveguide comprises a third phase modulator configured to be driven at a third phase and a fourth phase modulator configured to be driven at a fourth phase,
wherein the first phase, second phase, third phase, and fourth phase differ from each other, and
wherein N is greater than two.
17. The apparatus of claim 16 , further comprising at least one driver configured to drive the first phase modulator, second phase modulator, third phase modulator, and fourth phase modulator.
18. The apparatus of claim 16 , wherein the first optical waveguide and second optical waveguide are of substantially equal length.
19. The apparatus of claim 16 , wherein each of the N optical waveguides comprises a phase modulator optically proximate the 1×N input optical coupler and a phase modulator optically distal the 1×N input optical coupler, and wherein the phase modulators optically proximate the 1×N input optical coupler are driven at different phases from each other separated by 360°/N.
20. The apparatus of claim 19 , wherein the first phase and second phase differ from each other by 90 degrees.