Design considerations for plasmonic-excitation based optical detection of liquid and gas media in infrared

Surface plasmon resonance (SPR) sensor schemes based on silicon (Si) and chalcogenide glass are evaluated and compared for chemical as well as gas detection in a wide range of infrared (IR) wavelengths. The plasmonic characteristics in IR are critically dependent on the dispersive behavior of the coupling substrate material. The performance of sensor has been evaluated in terms of its intrinsic sensitivity (IS) that includes the FWHM and angular shift of SPR curve for a given change in refractive index of sensing medium. Both these materials are potential candidates for opening up new routes for detection in near- and mid-IR due to their strong dispersion capabilities as compared to normal silica-based glass. The IS of chalcogenide glass-based SPR sensor is found to be larger than Si-based one for a broad wavelength range of 700–2500 nm indicating that chalcogenide glass-based probe provides more sensitive as well as accurate sensing procedure than Si-based probe. Further, for both glasses, the single probe can be used for both aqueous as well as gaseous sensing. Furthermore, for both glasses, it is found that the values of IS are much larger for gaseous sensing in comparison to liquid sensing.