Two-wavelength and power-balanced oscillation of a CO2 laser for application to differential absorption measurements |
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| Authors: | Mostafa Hamza Takao Kobayasi Humio Inaba |
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| Institution: | (1) Research Institute of Electrical Communication, Tohoku University, Katahira 2-1-1, 980 Sendai, Japan;(2) Present address: Department of Electrical Engineering, Fukui University, Bunkyo 3-9-1, 910 Fukui, Japan |
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| Abstract: | A new technique of alternate two-wavelength oscillation of a CO2 laser is discussed for application to various differential absorption spectroscopic measurements. Power-balanced, two-adjacent branch oscillation using a single CO2 laser was achieved by modulating the angle of a mirror inside the laser cavity and adjusting automatically the cavity length. The two-wavelength modulation frequency was extended up to about 1.2 kHz. Line tuning and power modulation characteristics were studied. The laser was used in long-path differential absorption measurements of ethylene air pollution molecules to demonstrate the capability of this power-balanced, two-wavelength oscillation method. The minimum detectable absorption was nearly 1×10–3 in a short-path cell experiment and 3×10–3 in a long-path experiment. |
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