Volatile Gas Sensing through Terahertz Pipe Waveguide

• Published in: Sensors (Basel, Switzerland) Vol. 20; no. 21; p. 6268
• Main Authors: Lu, Ja-Yu, You, Borwen, Wang, Jiun-You, Jhuo, Sheng-Syong, Hung, Tun-Yao, Yu, Chin-Ping
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 03.11.2020; MDPI
• Subjects: anti-resonant reflection optical waveguide (ARROW); Dipole moments; Electrostatic discharges; Gas sensors; Gases; Letter; optical gas sensing; Pipes; Propagation; Radiation; Sensors; Spectrum analysis; Strong interactions (field theory); submillimeter wave; Terahertz frequencies; terahertz wave; waveguide sensor; Waveguides; anti-resonant reflection optical waveguide (ARROW); optical gas sensing; waveguide sensor; terahertz wave; submillimeter wave
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s20216268

Gas sensing to recognize volatile liquids is successfully conducted through pipe-guided terahertz (THz) radiation in a reflective and label-free manner. The hollow core of a pipe waveguide can efficiently deliver the sensing probe of the THz confined waveguide fields to any place where dangerous vapors exist. Target vapors that naturally diffuse from a sample site into the pipe core can be detected based on strong interaction between the probe and analyte. The power variation of the THz reflectance spectrum in response to various types and densities of vapors are characterized experimentally using a glass pipe. The most sensitive THz frequency of the pipe waveguide can recognize vapors with a resolution at a low part-per-million level. The investigation found that the sensitivity of the pipe-waveguide sensing scheme is dependent on the vapor absorption strength, which is strongly related to the molecular amount and properties including the dipole moment and mass of a gas molecule.