SiC has emerged as a highly promising material for harnessing nonlinear processes, attributed to its inherent χ(2) and χ(3) nonlinearities. The recent introduction of SiC-on-insulator nanowaveguides with high-index contrast has enabled efficient dispersion engineering and strong light-matter nonlinear interaction. This advancement has consequently led to various nonlinear phenomena, including the generation of Kerr combs, supercontinuum, and second harmonic signals. Notably, none of the existing demonstrations have combined χ(2) and χ(3) nonlinear processes within a single device. In this study, we present a dispersion-engineered 4H-SiC-on-insulator nanowaveguide, which not only allows for the generation of octave-spanning supercontinuum through dispersive wave generation but also enables efficient frequency doubling of this dispersive wave. Our demonstration shows that the 4H-SiC-on-insulator is a versatile integrated platform for compact, multifunctional nonlinear devices.
A strip titanium dioxide (TiO2) waveguide is designed for highly coherent mid-infrared (MIR) supercontinuum (SC) generation. For the designed TiO2 waveguide, three zero-dispersion wavelengths (ZDWs) are obtained through adjusting the waveguide structure parameters. The three ZDWs are located at 1.53, 3.96, and 5.43 μm, respectively. The nonlinearity coefficient γ is calculated as 1.12 W − 1 m − 1 at wavelength 3.1 μm. By optimizing the pump pulse parameters, the highly coherent MIR SCs are generated when the hyperbolic secant pump pulse with a duration of 80 fs, peak power of 1 kW, and wavelength of 3.1 μm is launched into the TiO2 waveguide and propagated 4.2-mm in length. The obtained SC covers a wavelength range from 1.71 to 9.90 μm (more than 2.5 octaves). Our research results can find important applications in MIR photonics and spectroscopy, biophotonics, optical precision measurement, etc.
We propose the two-stage cascaded-tapered silica photonic crystal fiber (PCF) for the supercontinuum (SC) generation. The cascaded-tapered silica PCF is designed to have a spatial periodic structure. The physical scenarios of the spectral broadening due to the interaction between the structure-induced periodic dispersion and Kerr nonlinearity under different pulse widths and peak powers are investigated. It is found that when the pump pulses with width of <100 fs and peak power of not more than 10 kW are propagated in the cascaded-tapered silica PCF, the SC with good coherence can be generated. It is believed that the research results have potential applications in the nonlinear photonics and spectroscopy.
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