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Real-time spectroscopic sensing using a widely tunable external cavity-QCL with MOEMS diffraction grating

: Ostendorf, R.; Butschek, L.; Merten, A.; Grahmann, J.; Jarvis, J.P.; Hugger, S.; Fuchs, F.; Wagner, J.


Razeghi, M. (Ed.) ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Quantum Sensing and Nano Electronics and Photonics XIII : San Francisco, California, United States, February 13, 2016
Bellingham, WA: SPIE, 2016 (Proceedings of SPIE 9755)
ISBN: 9781628419900
Paper 975507, 8 S.
Conference "Quantum Sensing and Nano Electronics and Photonics" <13, 2016, San Francisco/Calif.>
Fraunhofer IAF ()
tunable infrared laser; quantum cascade laser; external cavity laser; spectroscopic process analysis; gas sensing

We present spectroscopic measurements performed with an EC-QCL combining a broadly tunable quantum cascade laser chip with a tuning range of more than 300 cm-1 and a resonantly driven MOEMS scanner with an integrated diffraction grating for wavelength selection in Littrow configuration. The grating geometry was optimized to provide high diffraction efficiency over the wide tuning range of the QCL, thus assuring high power density and high spectral resolution in the MIR range. The MOEMS scanner has a resonance frequency of 1 kHz, hence allowing for two full wavelength scans, one up and the other downwards, within 1 ms. The capability for real-time spectroscopic sensing based on MOEMS EC-QCLs is demonstrated by transmission measurements performed on polystyrene reference absorber sheets as well as on gaseous samples of carbon monoxide. For the latter one, a large portion of the characteristic CO absorption band containing several absorption lines in the range of 2070 cm-1 to 2280 cm-1 can be monitored in real-time.