Theoretical Investigation of Broadband Frequency Conversion Bridging the Mid-Infrared and Telecom Band Through a Chalcogenide/Sio2 Hybrid Waveguide

Capturing the distinctive spectral fingerprints of molecules in the infrared (IR) region is of vital importance in gas detection. However, it is still limited by the resolution, sensitivity and signal to noise ratio of IR detectors. Here, a broadband frequency conversion scheme from the middle IR band (MIR) to the telecom band based on four-wave mixing process is proposed and theoretically investigated, combining the advantages of well-established detectors in the telecom band and unique molecular vibrations in the MIR band. A flat and low dispersion profile is generated in an asymmetric Ge-As-Se/SiO
₂
hybrid waveguide, which exhibits four zero-dispersion wavelengths and a dispersion variation of sub-20 ps/nm/km. Furthermore, taking advantage of the high order phase-matching, an ultra-broad 3-dB continuous wavelength conversion bandwidth covering 1454-4521 nm is achieved, which to the best of our knowledge is the widest frequency conversion bandwidth in the chip-scale devices. In addition, a fabrication scheme is proposed for the precise manipulation of dispersion. It holds great potential for practical applications in photonic integrated gas sensing, biomedical diagnostics.