Design of a mid-infrared multispecies gas sensor based on Pr3+-doped chalcogenides waveguides

Praseodymium-doped selenide thin films are deposited by radio frequency (RF) magnetron sputtering on thermally oxidized silicon wafers. Ridge waveguides are then processed using photolithography and dry etching techniques. Under optical pumping at 1.55 μm, broadband guided midinfrared photoluminescence is recorded between 3.5 and 5.5 μm. Optical design confirmed that these active waveguides allow single-mode optical propagation at different absorption wavelengths of important environmental gases (CO₂, CO, NO). Mid-Wave Infrared (MWIR) multimode interferometer (MMI)-based demultiplexer are designed for multispecies gas sensing.