Abstract
A pulsed, distributed feedback (DFB) quantum cascade (QC) laser centered at was used in combination with an off-axis cavity enhanced absorption (CEA) spectroscopic technique for the detection of ammonia and ethylene. Here, the laser is coupled into a high-finesse cavity with an optical path length of . The cavity is installed into a long sample cell with a volume of . The laser is excited with short current pulses (), and the pulse amplitude is modulated with an external current ramp, resulting in a frequency scan. A demodulation approach followed by numerical filtering was utilized to improve the signal-to-noise ratio. We demonstrated detection limits of ~15 ppb and for ammonia and ethylene, respectively, with less than averaging time.
© 2010 Optical Society of America
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