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Proceedings Paper

Application of quantum cascade lasers for infrared spectroscopy of jet-cooled molecules and complexes
Author(s): Yunjie Xu; Xunchen Liu; Zheng Su; Raviraj M. Kulkarni; Wai Shun Tam; Cheolhwa Kang; Igor Leonov; Lisa D'Agostino
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Paper Abstract

The combination of infrared laser spectroscopy with a molecular jet expansion provides a powerful technique to investigate medium sized organic molecules and clusters. The coupling of quantum cascade lasers (QCLs) with two slit jet infrared spectrometers, namely an off-axis cavity enhanced absorption (CEA) spectrometer and a rapid scan spectrometer with an astigmatic multi-pass cell assembly, are described. Two types of QCLs, specifically a continuous wave (cw) liquid nitrogen cooled distributed-feedback QCL at 5.7 μm, and a cw room temperature mode-hop-free external cavity QCL centered at 6.1 μm, were employed as the light sources. A pair of 1 inch highly reflective cavity ring-down mirrors (R = 99.98% at 5.2 μm) separated by 55 cm or a pair of 1.5 inch astigmatic mirrors separated by 20 cm, served as the optical cavities. To automate and to synchronize the timing of the CEA or rapid scan experiments with a pulsed slit jet molecular expansion, two LabVIEW computer programs were developed. For the CEA experiments, one of the cavity mirrors was mounted on a piezoelectric actuator with 1 inch clear aperture to maximize the effective mirror size. The effects of mirror size and laser sweep rate were evaluated. A minimum detection sensitivity of 1.8×10-8 cm-1 was achieved. Jet-cooled molecules were generated using a homemade pulsed slit jet nozzle assembly. A jet-cooled infrared spectrum of methyl lactate was recorded to demonstrate the performance of the CEA spectrometer. Preliminary results obtained with the room temperature QCL coupled to the rapid scan spectrometer are also presented.

Paper Details

Date Published: 26 January 2009
PDF: 11 pages
Proc. SPIE 7222, Quantum Sensing and Nanophotonic Devices VI, 722208 (26 January 2009); doi: 10.1117/12.814878
Show Author Affiliations
Yunjie Xu, Univ. of Alberta (Canada)
Xunchen Liu, Univ. of Alberta (Canada)
Zheng Su, Univ. of Alberta (Canada)
Raviraj M. Kulkarni, Univ. of Alberta (Canada)
Wai Shun Tam, Univ. of Alberta (Canada)
Cheolhwa Kang, Univ. of Alberta (Canada)
Igor Leonov, Univ. of Alberta (Canada)
Lisa D'Agostino, Univ. of Alberta (Canada)

Published in SPIE Proceedings Vol. 7222:
Quantum Sensing and Nanophotonic Devices VI
Manijeh Razeghi; Rengarajan Sudharsanan; Gail J. Brown, Editor(s)

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