Photonic crystal fiber sensors in the THz domain: A leap forward in alcohol detection.

Methanol (CH₃OH) is a volatile, transparent, and toxic substance widely used in chemical substrates, antifreeze, and industrial applications. Ethanol (C₂H₅OH), in contrast, is commonly used in alcoholic beverages, as a fuel additive, and as an antiseptic. Differentiating between methanol and ethanol is critical due to the severe health risks associated with methanol ingestion, while ethanol is safe for consumption in moderation. To tackle this challenge, we present a highly sensitive and accurate Photonic Crystal Fiber (PCF) sensor designed for the detection of both methanol and ethanol. The proposed sensor demonstrates impressive performance, with maximum relative sensitivities (RS) of 95.72 % for methanol and 97.55 % for ethanol, while operating within the 2.2 to 3.2 THz range. Additionally, it achieves low Effective Material Loss (EML) values of 0.0066 cm⁻ for ethanol and 0.0044 cm⁻ for methanol, with Numerical Aperture (NA) values of 0.257 and 0.270, respectively. The key advantages of this sensor include its exceptional precision, high sensitivity, and low material loss, making it a reliable solution for accurately distinguishing between methanol and ethanol in various industrial and commercial applications. By providing enhanced detection capability in the THz range, this sensor improves safety monitoring and quality control processes in sectors where these substances are frequently used.