Terahertz Optical Sensor based on Helically Twisted Photonic Crystal Fiber for Toxic Gases Sensing

Abstract A helically twisted photonic crystal fiber (PCF) gas sensor composed of 12 hollow pipes around the core in the cladding region is proposed and examined in the 0.3-3.0 terahertz (THz) frequency range for sensing toxic gases. The suggested THz optical sensor has been designed and simulated using the finite-difference eigenmode (FDE) method. The sensor with one twist along 50 cm- fiber exhibits four frequency bands with very low loss and high detection percentage. For each frequency band of toxic gases with nG = 1.00, 1.02, 1.04, 1.06 and 1.08, the refractive index sensitivity of 1450, 2250, 3000, and 2550 GHz/RIU are obtained, respectively. Furthermore, transmission loss and figure of merit (FOM) have been obtained as 10⁻⁴-10⁻² 1/cm and 50 - 250 1/RIU, respectively. Finally, the proposed THz sensor is shown to be a very good candidate for sensing toxic gases owing to its high performance and simple structure.