High-sensitivity transient spectroscopy using tunable diode lasers |
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Authors: | J E Hayward D T Cassidy J Reid |
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Institution: | (1) McMaster University, L8S 4M1 Hamilton, Ontario, Canada;(2) Present address: Lumonics Inc., 105 Schneider Road, K2K 1Y3 Kanata, Ontario, Canada |
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Abstract: | Experimental techniques have been developed to monitor transient infrared absorptions using lead-salt tunable diode lasers. The techniques are easily implemented, yield sensitivities which are limited by detector noise at 10–5 level of absorbance, and have a response time on the order of one microsecond. The transient absorption detection techniques are high frequency versions of the sweep integration technique pioneered by Jennings Appl. Opt.19, 2695 (1980)]. TDL modulation rates of 100 kHz and 500 kHz allow for absorption sampling rates of 200 kHz and 1 MHz, respectively. In order to reproducibly achieve near-detector-noise-limited sensitivities for 100 kHz TDL modulation rates, an automated analog subtraction circuit has been developed which removes the effects of minor TDL power variations. At the 500 kHz modulation rate, digital filtering techniques are used to remove the effects of this power variation. |
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Keywords: | 42 60Kg 35 80+s |
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