| Summary: | 碩士 === 國立臺灣大學 === 光電工程學研究所 === 103 === In this thesis, the CO2 gas sensing system with multi-wavelength detection is demonstrated by means of narrow bandwidth triple-wavelength thermal emitter and corresponding narrow bandwidth plasmonic photodetectors. In addition to detecting the two absorption of CO2 in mid-infrared spectrum, a reference signal which would not be absorbed by CO2 makes the whole system more reliable and can be used to calibrate the variation of the emitter.
Firstly, an Au/SiO2/Au grating structure with two widths is fabricated on top of a waveguide mode thermal emitter with random-hole patterned. With one waveguide mode generated from the bottom and a localized surface plasmon (LSP) mode and a propagating surface plasmon (SP) mode generated from the top, the triple-wavelength thermal emitter can be realized. By controlling the thickness of a-Si:H film on top of the plasmonic photodetector, the specific wavelength detection can be carried out. With waveguide mode photodetector, the short wavelength detection can be achieved.
By designing an emitter chamber, a gas chamber, a detector holder and the devices discussed above, a CO2 gas sensing system with multi-wavelength detection is carried out. The CO2 concentration which is exhaled from a healthy human is successfully detected by varying the length of the gas chamber and the emission intensity of the thermal emitter. Besides, the reference detector can be used to detect the emission intensity from the triple-wavelength thermal emitter for monitoring the degeneration of the light source and make the whole system more reliable.
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