All-optical flip-flop and control methods thereof
Embodiments of the invention pertain to remote optical control of holding beam-type, optical flip-flop devices, as well as to the devices themselves. All-optical SET and RE-SET control signals operate on a cw holding beam in a remote manner to vary the power of the holding beam between threshold switching values to enable flip-flop operation. Cross-gain modulation and cross-polarization modulation processes can be used to change the power of the holding beam.
1. A remote-control signal, holding beam-type, all-optical flip-flop device, comprising:
a non-linear, optical, bistable medium characterized by an upward switching threshold and a downward switching threshold;
a nonlinear, holding beam power modulator that can effect an increase and a decrease in the power of the holding beam, located remotely from the bistable medium;
a holding beam generator that can generate a holding beam that can operatively engage the nonlinear holding beam power modulator;
a holding beam propagation medium intermediate the nonlinear holding beam power modulator and the bistable medium;
at least one control signal generator that can generate at least one of an optical SET control signal and an optical RE-SET control signal; and
an optical control signal propagation medium disposed intermediate the at least one control signal generator and the nonlinear holding beam power modulator.
2. The device of claim 1 , wherein the at least one control signal generator comprises an optical SET control signal generator and an optical RE-SET control signal generator.
3. The device of claim 1 , wherein the optical control signal propagation medium is an optical RE-SET control signal propagation medium and an optical SET control signal propagation medium.
4. The device of claim 1 , wherein the bistable medium is a dispersive bistability medium.
5. The device of claim 4 , wherein the dispersive bistability medium is a resonant type semiconductor optical amplifier (RT-SOA).
6. The device of claim 5 , wherein the resonant type semiconductor optical amplifier is a vertical cavity surface-emitting semiconductor optical amplifier (VC-SOA).
7. The device of claim 5 , wherein the resonant type semiconductor optical amplifier is a Fabry-Perot SOA.
8. The device of claim 5 , wherein the resonant type semiconductor optical amplifier is a distributed feedback SOA.
9. The device of claim 5 , wherein the resonant type semiconductor optical amplifier is a ring-resonator with an internal SOA.
10. The device of claim 1 , wherein the bistable medium is an absorptive bistability medium.
11. The device of claim 1 , wherein the bistable medium is a combination dispersive/absorptive bistability medium.
12. The device of claim 1 , wherein the bistable medium is a four-wave mixing bistability medium.
13. The device of claim 1 , wherein the holding beam propagation medium is an optical waveguide.
14. The device of claim 1 , wherein the optical control signal propagation medium is an optical waveguide.
15. The device of claim 1 , wherein the nonlinear, holding beam power modulator is an optical amplifier.
16. The device of claim 15 , wherein the optical amplifier is a travelling-wave semiconductor optical amplifier.
17. The device of claim 1 , wherein the nonlinear, holding beam power modulator includes a nonlinear birefringent medium followed by a wave plate and a polarizer.
18. A method for controlling a holding beam-type, all-optical flip-flop device, comprising:
generating an optical SET control signal pulse and an optical RE-SET control signal pulse;
generating a continuous-wave holding beam;
propagating the holding beam through a nonlinear, holding beam power modulator and into a non-linear, optical, bistable medium characterized by an upward switching threshold and a downward switching threshold; and
propagating the optical RE-SET control signal and the optical SET control signal through the nonlinear, holding beam power modulator and decreasing and increasing the power of the holding beam, respectively.
19. The method of claim 18 , comprising changing the power of the holding beam by a cross-gain modulation (XGM) process.
20. The method of claim 18 , comprising changing the power of the holding beam by a cross-polarization rotation process.
21. The method of claim 18 , comprising generating each optical SET control signal pulse and optical RE-SET control signal pulse from a common control signal pulse.
22. The method of claim 18 , wherein the optical SET control signal is polarization independent.
23. The method of claim 18 , wherein the optical RE-SET control signal is polarization independent.