Subwavelength-Engineered Suspended Silicon Waveguide for Long-Wave Infrared Sensing Applications

Many volatile organic compounds (VOCs) are regarded as major indoor pollutants and potentially threaten human health in the short- and long-term. Several VOCs are also indicators for specific diseases. Thus, portable and selective detection of VOCs is highly desired. In this letter, a chip-scale subwavelength-engineered suspended silicon waveguide platform working in the long-wave infrared is demonstrated for toluene vapor detection. The broadband characterization of this platform is presented and a flat transmission spectrum over the measured wavelength range is shown. With 3.8 dB/cm propagation loss achieved at the toluene absorption fingerprint of 6.65 µm, the limit of detection of toluene sensing reaches 6 ppm. The response and recovery time to the 6 ppm toluene are 3.0 and 5.6 s, respectively. This chip-scale optical gas sensing platform is a promising candidate for on-site real-time environmental monitoring and medical diagnosis.