Mid-infrared integrated spectroscopic sensor based on chalcogenide glasses: Optical characterization and sensing applications

A mid-infrared (mid-IR) spectroscopic sensor is developed using a chalcogenide glasses (ChGs) platform with a broad transmission band. The ridge ChGs waveguides were patterned via standard i-line photolithography and reactive ion etching, following the deposition of guiding and confinement layers through RF magnetron sputtering. The waveguides exhibit a wide transparency range from λ ​= ​3.94–8.95 ​μm, with minimum propagation losses value of 2.5 ​dB/cm at λ ​= ​7.58 ​μm. To validate the feasibility of the suggested sensor, a spectroscopic gas sensing experiment was performed using CO₂, resulting in an estimated limit of detection (LoD) of 1.16%v at λ ​= ​4.28 ​μm, achieved with an external confinement factor Γ of 6.5%. Additionally, liquid sensing experiment was carried out using isopropanol, obtaining a LoD of 300 ppmv at λ ​= ​7.25 ​μm.