Cover story: Zhe L, Hang Y, Wu H, et al. Self-phase modulation in integrated cadmium telluride polycrystalline waveguide[J]. Opto-Electron Eng, 2023, 50(2): 220313

The mid-infrared band (2.5-25 µm) contains vibrational and rotational absorption lines of most molecules, making it important for molecular spectral applications, such as gas sensing, environmental monitoring, and disease diagnosis.One way is to output coherent mid-infrared laser through OPA in nonlinear crystals, such as ZnGeP2, LiGaSe2, and GaSe. However, the absorption boundary of these nonlinear crystals limits the generation of longer wavelength mid-infrared lasers. Semiconductor integration technology can be used to process materials without absorption of mid-infrared wavelength to produce on-chip nonlinear waveguides, further expand the spectrum coverage, enhance the design freedom, minimize, improve reliability, reduce cost, etc.

Professor Houkun Liang's research team from Sichuan University, designed and processed a new on-chip CdTe integrated waveguide based on CdTe as the core layer, low refractive index medium cadmium sulfide as the buffer layer, and silicon as the substrate.This work provides an experimental basis for realizing the mid-infrared supercontinuum on CdTe integrated waveguide. By further improving the coating process and solving the problem of mid-infrared femtosecond pump light source, it is possible to achieve supercontinuum with a wavelength up to 20 µm.