Chalcogenide fiber-optic SPR chemical sensor with MoS2 monolayer, polymer clad, and polythiophene layer in NIR using selective ray launching

Surface plasmon resonance (SPR) based chalcogenide fiber-optic sensor with polymer clad and MoS2 monolayer is simulated and analyzed in near infrared (NIR) for detection of mixture of alcohols (ethanol and methanol) dissolved in water solution. The proposed fiber optic sensor is analyzed under angular interrogation method, which is based on selective ray (on-axis) launching of monochromatic light into the fiber core at varying angle followed by measuring the loss of power (in dB) after passing through the SPR probe region. The performance of the sensor is analyzed in terms of its figure of merit (FOM). The sensor's specificity towards alcohols along with considerably larger FOM is achieved by utilizing a polythiophene (PT) layer. The results indicate that longer NIR wavelength (lambda) provides superior sensing performance. The sensor's performance is better for larger volume fraction of methanol in the water solution. The proposed fiber optic SPR sensor has the capability of providing much greater FOM compared with the previously-reported SPR sensors.