Real-time monitoring of toxic CS2 with high concentrations using a suitable terahertz photonic crystal fiber

Abstract

Detection of toxic carbon disulfide ( C S 2 ) at high concentration, arising due to heavy industrial utilities, is an essential requirement for a sustainable ecosystem and healthcare. However, research and development of appropriate sensor devices to monitor a very high concentration of C S 2 are lacking. We design a polyethylene (PE) photonic crystal fiber (PCF) consisting of two interpenetrating periodic hexagonal lattices of teflon inclusions and air holes in the cladding, which can monitor ambient C S 2 with extremely high precision in a wide concentration range. Here, we measure the time delay difference (TDD) associated with the difference between group velocities of the two supported modes due to changes in C S 2 concentration in the prescribed holes. For a 10 cm long variant of the designed PCF operating at 0.75 THz frequency, we observe a linearly increasing TDD variation from ∼ 2 to 13 ps due to change in C S 2 concentration from 17 to 50%. However, when the C S 2 concentration exceeds the 50% range, we observe decreasing TDD characteristics. In this high concentration regime ( > --> 50 % ), we monitor C S 2 by analyzing second mode loss (SML) variation due to concentration change (at 0.98 THz frequency), where SML increases up to ∼ 30 d B for ∼ 100 % ambient C S 2 concentration. Here, we achieve a high concentration sensitivity where a variation of 1.6 dB SML is observed with a unit concentration change of C S 2 . The proposed scheme has an immense potential to boost the technologies for high-precision gas monitoring devices.