Haiyan Ou | Searcharxiv

arXiv2026

Widely tunable optical parametric oscillation and visible light generation in 4H-SiC microresonators

Widely separated optical parametric oscillation (OPO) represents a powerful method for coherent wavelength conversion across infrared and visible spectra. While such generation has been demonstrated in material platforms like silicon nitride and lithium niobate, 4H-SiC remains unexplored despite offering combined strong second-order and third-order nonlinearities with ultralow material loss. Here we demonstrate tunable, widely separated OPO generation in 4H-SiC microresonators through dispersion engineering. By optimizing the resonator geometry to achieve normal dispersion at telecommunication wavelengths and pumping at around 1550 nm, a pair of signal and idler spanning nearly an octave is generated,which represents the first demonstration of widely separated OPO in 4H-SiC. The frequency separation is tuned by varying the pump wavelength, with measured signal and idler wavelengths align well with phase-matching prediction. Leveraging the non-centrosymmetric crystal structure of 4HSiC, the generated OPO signal undergoes cascaded second-harmonic generation (SHG) and sum-frequency generation (SFG) with the pump, yielding coherent visible light at wavelengths below 700 nm. This cascaded upconversion of widely separated OPO signals represents a novel pathway for visible light generation. These results establish 4H-SiC as a promising platform for nonlinear wavelength conversion spanning from visible to 2 um region.

physics.optics↗

arXiv2023

Efficient Raman lasing and Raman-Kerr interaction in an integrated silicon carbide platform

Implementing stimulated Raman scattering in a low-loss microresonator could lead to Raman lasing. Here, we report the demonstration of an efficient Raman laser with $>50 \%$ power efficiency in an integrated silicon carbide platform for the first time. By fine tuning the free spectral range (FSR) of 43-$μ$m-radius silicon carbide microresonators, the Stokes resonance corresponding to the dominant Raman shift of $777\ \text{cm}^{-1}$ ($23.3$ THz) is aligned to the center of the Raman gain spectrum, resulting in a low power threshold of $2.5$ mW. The peak Raman gain coefficient is estimated to be ($0.75 \pm 0.15) \ \text{cm}/\text{GW}$ in the 1550 nm band, with an approximate full width at half maximum of ($120 \pm 30$) GHz. In addition, the microresonator is designed to exhibit normal dispersion at the pump wavelength near 1550 nm while possessing anomalous dispersion at the first Stokes near 1760 nm. At high enough input powers, a Kerr microcomb is generated by the Stokes signal acting as the secondary pump, which then mixes with the pump laser through four-wave mixing to attain a wider spectral coverage. Furthermore, cascaded Raman lasing and occurrence of multiple Raman shifts, including $204\ \text{cm}^{-1}$ ($6.1$ THz) and $266\ \text{cm}^{-1}$ ($8.0$ THz) transitions, are also observed. Finally, we show that the Stokes Raman could also help broaden the spectrum in a Kerr microcomb which has anomalous dispersion at the pump wavelength. Our example of a 100-GHz-FSR microcomb has a wavelength span from 1200 nm to 1900 nm with 300 mW on-chip power.

physics.optics↗