INTRACAVITY LASER SPECTROSCOPY WITH A $Co:MgF_{2}$ LASER IN THE $1.6-2.5 \mu$m REGION-ULTRASENSITIVE TECHNIQUE FOR TRACE GAS MONITORING
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Date
1999
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Ohio State University
Abstract
The characteristics of a $Co:MgF_{2}$ laser are examined with respect to intracavity laser spectroscopy. This laser can be operated in a CW regime and has the broad tunability range from 1.6 to $2.5 \mu$m. Many vibrational and overtone transitions of molecules and radicals appear in this spectral region. Optically pumped by $1.34 \mu$m laser radiation, the broadband pulsed $Co:MgF_{2}$ laser has been operated at room temperature. We were able to obtain 1-ms-duration pulses. The IR $Co:MgF_{2}$ laser radiation has been up-converted to visible region and spectrally analyzed by a grating spectrograph. The spectra were recorded by a CCD array. The spectral resolution of the recording was $0.05 cm^{-1}$. The intracavity absorption spectra of atmospheric carbon dioxide and water vapor were recorded in the $2.03 - 2.06 \mu$m spectral region. The intracavity absorption spectra of ammonia, methane, ethane, methanol, water vapor, methyl iodide, and transient products of flash photolysis of acetone were recorded in the $2.23 - 2.25 \mu$m spectral region. The linear growth of the intracavity absorption was observed for the generation time values from 0 to at least 1 ms which is equivalent to the detection sensitivity of $3 \cdot 10^{-9} cm^{-1}$. Numerous atmospheric trace gases with resolved absorption spectra can be monitored at the ppb-level concentrations (1 part in $10^{9}$) with this sensitivity.
Description
Author Institution: Physical Institute, Russian Academy of Sciences