Optical isolator using phase modulators
View Patent ↗Various exemplary embodiments relate to an optical isolator in an integrated optical circuit including: a first optical modulator configured to provide a first periodic phase modulation on an input optical signal; a second optical modulator configured to provide a second periodic phase modulation on the modulated optical signal; and an optical waveguide having a length L connecting the first optical modulator to the second optical modulator; wherein the phase difference between the first and second periodic phase modulation is π/2, and wherein the length L of the optical waveguide causes a phase delay of π/2 on an optical signal traversing the optical waveguide.
1. An optical isolator for use in an integrated optical circuit comprising:
a first optical modulator configured to provide a first periodic phase modulation on an input optical signal;
a second optical modulator configured to provide a second periodic phase modulation on the modulated optical signal; and
an optical waveguide having a length L connecting the first optical modulator to the second optical modulator;
wherein the phase difference between the first and second periodic phase modulation is π/2, and
wherein in use the length L of the optical waveguide causes a phase delay of π/2 on an optical signal traversing the optical waveguide.
2. The optical isolator of claim 1 , further comprising a first optical bandpass filter connected to the first phase modulator.
3. The optical isolator of claim 2 , further comprising a second optical bandpass filter connected to the second phase modulator.
4. The optical isolator of claim 2 , wherein the first optical bandpass filter has a bandwidth of less than approximately 2 f where f is a frequency of the first and second periodic modulations.
5. The optical isolator of claim 1 , wherein L=v g ΔT, where v g is the group velocity in the waveguide, and ΔT satisfies ωΔT=π/2 where ω is a frequency of the first and second periodic modulations.
6. The optical isolator of claim 1 , wherein the first periodic phase modulation is A cos(ωt) and the second periodic phase modulation is A sin(ωt).
7. The optical insulator of claim 6 , wherein A substantially satisfies the relationship J 0 (2A)=0.
8. The optical isolator of claim 1 , wherein the optical isolator is configured to isolate the output of a continuous wave laser.
9. A method of isolating the output of a laser source comprising:
optically phase modulating the output of the laser source with a first periodic phase modulation;
transmitting the optically phase modulated signal on an optical waveguide that phase delays the optically phase modulated signal by π/2;
optically phase modulating the transmitted optically phase modulated signal with a second periodic phase modulation wherein the phase difference between the first and second periodic phase modulation is π/2.
10. The method of claim 9 , further comprising optically filtering the input optical signal.
11. The method of claim 10 , wherein optically filtering the input optical signal has a bandwidth of less than approximately 2 f where f is a frequency of the first and second periodic modulations.
12. The method of claim 10 , further comprising after optically phase modulating the transmitted optically phase modulated signal, optically filtering the resulting optical signal.
13. The method of claim 9 , further comprising after optically phase modulating the transmitted optically phase modulated signal, optically filtering the resulting optical signal.
14. The method of claim 13 , wherein optically filtering the resulting optical signal has a bandwidth of less than approximately 2 f where f is a frequency of the first and second periodic modulations.
15. The method of claim 9 , wherein the first periodic phase modulation is A cos(ωt) and the second periodic phase modulation is A sin(ωt).
16. The method of claim 15 , wherein A substantially satisfies the relationship J 0 (2A)=0.
17. An optical isolator for use in an integrated optical circuit comprising:
a first optical modulator having a first input/output port, a second input/output port, and a modulation port;
a first periodic source providing a first periodic modulation signal to the modulation port of the first optical modulator;
a second optical modulator having a first input/output port, a second input/output port, and a modulation port;
a second periodic source providing a second periodic modulation signal to the modulation port of the second optical modulator; and
an optical waveguide having a length L connecting the second input/output port of the first optical modulator to the first input/output port of the second optical modulator;
wherein the phase difference between the first and second periodic phase modulation signals is π/2, and
wherein in use the length L of the optical waveguide causes a phase delay of π/2 on an optical signal traversing the optical waveguide.
18. The optical isolator of claim 17 , further comprising a first optical bandpass filter connected to the first input/output port of the first phase modulator.
19. The optical isolator of claim 18 , further comprising a second optical bandpass filter connected to the second phase modulator.
20. The optical isolator of claim 17 , wherein the first periodic phase modulation is A cos(ωt) and the second periodic phase modulation is A sin(ωt).