Reconfigurable all-optical nonlinear activation functions on silicon-integrated platform
View Patent ↗Systems, devices, and methods are provided for all-optical reconfigurable activation devices for realizing various activations functions using low input optical power. The device and systems disclosed herein include a directional coupler comprising a first phase-shift mechanism and an interferometer coupled to the directional coupler. The interferometer comprises at least one microring resonator and a second phase-shift mechanism coupled to thereto. The interferometer and the directional coupler comprise waveguides formed of a first material, while the microring resonator comprises a waveguide formed of a second material and a third phase-shift mechanism. The second material is provided as a low-loss material having a high Kerr effect and large bandgaps, to generate various nonlinear activation functions. The first, second, and third phase-shift mechanisms are configured to control biases within the disclosed systems and devices to achieve a desired activation function.
1. An optical device comprising:
a directional coupler comprising a first phase-shift mechanism;
an interferometer coupled to the directional coupler, the interferometer comprising:
a first branch comprising a first waveguide formed of a first material and a second waveguide formed of a second material dissimilar to the first material,
a second branch comprising a third waveguide formed of the first material, and
a second phase-shift mechanism coupled to the first waveguide; and
a microring resonator coupled to the second waveguide, the microring resonator formed of the second material and comprising a third phase-shift mechanism,
wherein the first, second, and third phase-shift mechanisms are configured to control biases of the optical device to achieve a desired activation function.
2. The optical device of claim 1 , wherein the second material is a low loss material having a linear loss coefficient that is less than 200 dB/m.
3. The optical device of claim 1 , wherein the second material has a bandgap that is greater than 1.9 eV.
4. The optical device of claim 1 , wherein the second material has a nonlinear refractive index that is greater than 3×10 −20 m 2 /W.
5. The optical device of claim 1 , wherein the second material is aluminum gallium arsenide (AlGaAs).
6. The optical device of claim 1 , wherein the second material is tantalum pentoxide (Ta 2 O 5 ).
7. The optical device of claim 1 , wherein a ratio of a nonlinear refractive index to a linear loss coefficient of the second material is larger than 3×10 −20 .
8. The optical device of claim 1 , wherein the first waveguide comprises a junction end coupled to a junction end of the second waveguide, the optical device further comprising:
a first inverse taper pair comprising a first taper at the junction end of the first waveguide and a second taper at the junction end of the second waveguide, wherein the first taper is in an inverse direction relative to the second taper.
9. The optical device of claim 1 , wherein at least the third phase-shift mechanism comprises at least one of: a heterogeneous metal oxide semiconductor (MOS) phase shifter and a heater.
10. The optical device of claim 1 , wherein at least the third phase-shift mechanism comprises a heterogeneous metal oxide semiconductor (MOS) capacitor.
11. The optical device of claim 1 , wherein the directional coupler is a Mach-Zehnder coupler and the interferometer is a Mach-Zehnder interferometer.
12. A nonlinear activation device, comprising:
a Mach-Zehnder coupler (MZC) comprising a first phase-shift mechanism;
a Mach-Zehnder interferometer (MZI) coupled to the MZC, the MZI comprising a first branch that includes a first waveguide formed of a first material and a second waveguide formed of a second material that is dissimilar to the first material, and a second phase-shift mechanism coupled to the first waveguide; and
a microring resonator (MRR) coupled to the second waveguide, the microring resonator formed of the second material,
wherein the first and second phase-shift mechanisms are configured to control biases of the nonlinear activation device to switchably achieve a desired activation function,
wherein the second material comprises at least one of: (i) a bandgap over 1.9 eV; (ii) a nonlinear refractive index that is greater than 3×10 −20 m 2 /W, and (iii) a linear loss coefficient that is less than 200 dB/m.
13. The nonlinear activation device of claim 12 , wherein a ratio of a nonlinear refractive index to a linear loss coefficient of the second material is larger than 5×10 −20 .
14. The nonlinear activation device of claim 12 , wherein the second material is aluminum gallium arsenide (AlGaAs).
15. The nonlinear activation device of claim 12 , wherein the second material is tantalum pentoxide (Ta 2 O 5 ).
16. The nonlinear activation device of claim 12 , wherein the first waveguide comprises a first junction end coupled to a second junction end of the second waveguide, the optical device further comprising:
a first inverse taper pair comprising a first taper at the first junction end of the first waveguide and a second taper at the second junction end of the second waveguide, wherein the first taper is in an inverse direction relative to the second taper.
17. The nonlinear activation device of claim 16 , wherein the first waveguide comprises a third junction end coupled to a fourth junction end of the second waveguide, the optical device further comprising:
a second inverse taper pair comprising a third taper at the third junction end of the first waveguide and a fourth taper at the fourth junction end of the second waveguide, wherein the third taper is inverse relative to the fourth taper and inverse relative to the first taper.
18. A method for operating a nonlinear activation device, the method comprising:
adjusting a first bias of a Mach-Zehnder interferometer (MZI) included in the nonlinear activation device by controlling a first phase-shift mechanism of the MZI to tune a phase difference between branches of the MZI, wherein the first phase-shift mechanism is coupled to a first waveguide of a first branch of the MZI;
adjusting a second bias of a microring resonator (MRR), coupled to a second waveguide of the first branch of the MZI, such that the nonlinear activation device functions at approximately a resonance frequency of the MRR by controlling a second phase-shift mechanism of the MRR, the MRR is formed of a second material comprising at least one of: (i) a bandgap over 1.9 eV; (ii) a nonlinear refractive index that is greater than 3×10 −20 m 2 /W, and (iii) a linear loss coefficient that is less than 200 dB/m; and
adjusting a third bias of a Mach-Zehnder coupler (MZC), coupled to the MZI, to tune amplitudes of the branches of the MZI relative to one another by controlling a third phase-shift mechanism of the MZC,
wherein the first, second, and third bias are controlled to achieve a desired activation function, and
wherein the first waveguide is formed of a first material and the second waveguide is formed of the second material that is dissimilar to the first material.
19. The method of claim 18 , wherein the first, second, and third phase-shift mechanisms each comprise one of a heterogeneous metal oxide semiconductor (MOS) phase shifter or a heater.
20. The method of claim 18 , wherein the second material of the MRR is one of aluminum gallium arsenide (AlGaAs) and tantalum pentoxide (Ta 2 O 5 ).