多波段二氧化碳氣體偵測系統

CO2 Gas Sensing System with Multi-wavelength Detection

陳凱駿(Kai-Jyun Chen)

指導教授 ： 李嗣涔

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.10484

摘要

本論文主要研究利用多波段窄頻紅外線發射器以及室溫可操作的窄頻紅外線偵測器來實現多波段的二氧化碳氣體偵測系統。主要構想為藉由偵測二氧化碳在中紅外光的兩個窄頻吸收以及一個不會受到二氧化碳影響的波段來當作參考的信號使得整個氣體偵測系統可靠度更高。
我們在表面為隨機孔洞的波導型窄頻紅外線發射器上方製作結構為 金/二氧化矽/金 的光柵，而且這個光柵具有兩種不同的線寬。利用下方的波導模態以及上方的侷域型還有非侷域型模態來實現三波段的窄頻紅外線發射器。藉由探討覆蓋於窄頻紅外線偵測器上的非晶矽薄膜厚度與波長紅位移的關係來微調所要的偵測波段以及製作不同的窄頻紅外線偵測器。除此之外也利用波導模態來實現中紅外波段中波長較短的窄頻偵測器。
我們設計一個偵測系統來量測不同二氧化碳濃度，包含發射器腔體、氣體腔體、偵測器的載具以及上述的窄頻紅外線發射器與偵測器。藉由改變氣體腔體的長度以及窄頻紅外線發射器的發光強度，我們順利地偵測到人體吐出的二氧化碳濃度。利用不受二氧化碳影響的特性，當作參考信號用的偵測器也可以用來偵測窄頻紅外線發射器的發光強度，以監控光源的變化。

關鍵字

表面電漿子 ； 二氧化碳偵測 ； 紅外線發光元件 ； 紅外線光偵測器

並列摘要

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.

並列關鍵字

Surface plasmon ； CO2 detection ； infrared thermal emitter ； infrared photodetector

參考文獻

[2]. H.P. Chan, C. Lewis, and P.S. Thomas, Exhaled breath analysis: novel approach for early detection of lung cancer. Lung Cancer, 63(2): p. 164-168. (2009).

[4]. F. Laurent, M. Montaudon, and O. Corneloup, CT and MRI of lung cancer. Respiration, 73(2): p. 133-142. (2006).

[6]. A. Antczak, Markers of oxidative stress in exhaled breath condensate. NATO Science Series, Series, 1: p. 333-337. (2002).

[7]. M. Schweigkofler, and R. Niessner, Determination of siloxanes and VOC in landfill gas and sewage gas by canister sampling and GC-MS/AES analysis. Environmental science & technology, 33(20): p. 3680-3685. (1999).

[8]. M. Phillips, K. Gleeson, J.M.B. Hughes, J. Greenberg, R.N. Cataneo, L. Baker, and W.P. McVay, Volatile organic compounds in breath as markers of lung cancer: a cross-sectional study. The Lancet, 353(9168): p. 1930-1933. (1999).