A Dual-Band Carbon Dioxide Sensor Based on Metal–TiO2–Metal Metasurface Covered by Functional Material

Abstract

Highly sensitive and integrated optical multi-band CO2 sensors are significant at the shortwave infrared (SWIR) region and still lack research. A compact CO2 sensor composed of a Au-disk/TiO2-cylinder/Au-film metasurface coated by polyhexamethylene biguanide (PHMB) film, functioning at multi-band resonances as well as having high sensitivity to gas concentrations, is presented. It can be employed as a dual-band narrowband absorber, producing two strongly resonant modes at the SWIR region under a reflection-type framework of linearly polarized incidence. Moreover, the metasurface sensor possesses high refractive index sensitivity of 109.25 pm/ppm at around 1040 nm and 42.57 pm/ppm at around 1330 nm in the range of 200–600 ppm, which is suitable for detecting atmospheric CO2. Furthermore, the numerical results show that the sensitivity increases with a thicker PHMB film and optimizes at a thickness above 600 nm. The physical mechanism reveals that the higher order mode exhibits more extended near-field energy than the lower order mode, resulting in more sensitivity towards the surroundings. The design and results of our investigation show high-quality CO2 sensing performance which functions at dual spectrum bands in the SWIR region and is promising for integrated photonic applications.

Plasmonic Perfect Absorber Utilizing Polyhexamethylene Biguanide Polymer for Carbon Dioxide Gas Sensing Application

“…A design approach in [ 40 ] uses a metal-insulator-metal (MIM) waveguide-based structure coupled to a square-ring cavity filled with PHMB functional material to sense the CO 2 for a concentration range of 0–524 ppm. Concepts of dual-band CO 2 gas sensor is employed in [ 41 ], using a metasurface of metal-TiO 2 -metal covered with a functional material as a sensing polymer yielding sensitivities around 1040 and 1330 nm/ppm for a range of 200–600 ppm of concentration. A design of a CO 2 gas sensor based on silicon micro-ring refractometric is investigated in [ 42 ], using a coating of the functional layer to sense different concentrations, i.e., 0–500 ppm of the CO 2 gas, attaining a sensitivity value of 6 × 10 −9 RIU/ppm.…”