Tunable Mid-Infrared Dispersive Wave Generation of High-Efficiency and Broadband in a Suspended Thin-Film Lithium-Niobate-on-Insulator Waveguide

A suspended thin-film lithium-niobate-on-insulator nano-waveguide (NanoLN) is designed, and tunable mid-infrared dispersive wave generation of high-efficiency and broadband is numerically studied on this designed platform. By hollowing out the silicon dioxide substrate between the NanoLN core and silicon wafer, the loss issue induced by mode leaking at mid-infrared region is eliminated. The second zero-dispersion wavelength of the suspended NanoLN is tailored to locate around 2 μm wavelength, so that mode-locked fiber laser pump sources in this waveband can be conveniently leveraged to generate dispersive wave beyond 3 μm wavelength. We show that dispersive wave at 3.16 μm with high conversion efficiency up to 36.26% and bandwidth (at -10 dB level) of ~471 nm can be achieved at the pump pulse energy of 0.23 nJ. The central wavelength of the dispersive wave can be flexibly tuned up to 5 μm with a maximum -10 dB bandwidth of ~2 μm by lithographic control of the waveguide geometry, which is naturally at the expense of degraded conversion efficiency. Our results show the suspended NanoLN can provide a versatile chip-scale platform for cost-effective mid-infrared targetable, broadband, and coherent sources generation. Using fiber laser pump sources gives the advantages of compactness, free-maintenance, and long-term stability, which suit field applications.