Optical bi-stability in cubic silicon carbide microring resonators.

We measure the photothermal nonlinear response in suspended cubic silicon carbide (3C-SiC) and 3C-SiC-on-insulator (SiCOI) microring resonators. Bi-stability and thermo-optic hysteresis is observed in both types of resonators, with the suspended resonators showing a stronger response. A photothermal nonlinear index of 4.02×10-15 m2/W is determined for the suspended resonators, while the SiCOI resonators demonstrate one order of magnitude lower photothermal nonlinear index of 4.32×10-16 m2/W. Cavity absorption and temperature analysis suggest that the differences in thermal bi-stability are due to variations in waveguide absorption, likely from crystal defect density differences throughout the epitaxially grown layers. Furthermore, coupled mode theory model shows that the strength of the optical bi-stability, in suspended and SiCOI resonators can be engineered for high power or nonlinear applications.

All-optical, tunable, V- and W-band microwave generation using semiconductor lasers at period-one nonlinear dynamics with asymmetric mutual injection stabilization.

This study investigates an optically injected semiconductor laser operating at period-one nonlinear dynamics for all-optical microwave generation. A novel, to the best of our knowledge, all-optical stabilization scheme is proposed to greatly enhance the spectral purity of such generated microwaves, which sends a small fraction of the injected laser output back to the injecting laser, not the injected laser itself. Mutual injection with highly different injection power between the two lasers, i.e., highly asymmetric mutual injection, is thus formed. As a result, the microwave linewidth is reduced by up to at least 85 times, the phase noise variance is improved by up to at least 750 times, and a side-peak suppression ratio of more than 44 dB is achieved. Microwave generation that is tunable up to at least 110 GHz with a 3-dB linewidth down to below 2 kHz is realized.