FDTD Analysis of End-Fire Coupling Between Mid-IR On-Chip Light Sources on Si and As2Se3-on-CaF2 Waveguide from 3 to 8 µm for Spectroscopic Sensing

This work demonstrates that the As2Se3-on-CaF2 waveguide can enable optical integration with three distinct mid-infrared (mid-IR) light sources on silicon emitting at wavelengths of 3.6, 4.8, and 7.4 μm, while sustaining a competitive waveguide-based sensing figure of merit within a mid-IR spectral range of 3–8 µm. Despite considerable variations in lasing optical mode sizes and polarizations from three different laser chips, the As2Se3-on-CaF2 waveguide can facilitate efficient butt-coupling with each source while maintaining the same As2Se3 waveguide thickness. This permits the implementation of As2Se3-on-CaF2 waveguides, in which the waveguide width can be tailored to achieve both competitive optical coupling performance with the light sources and a high sensing figure of merit across the entire wavelength range of interest. This work demonstrates the attractiveness of the chalcogenide As2Se3-on-CaF2 waveguide in terms of design flexibility for chip-scale optical integration in the important mid-IR wavelength ranges.