Saturated absorption in a rotational molecular transition at 2.5 THz using a quantum cascade laser

We report on the evidence of saturation effects in a rotational transition of CH3OH around 2.5 THz, induced by a free-running continuous-wave quantum cascade laser (QCL). The QCL emission is used for direct-absorption spectroscopy experiments, allowing to study the dependence of the absorption coeff...

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Bibliographic Details
Published in:Applied physics letters 2015-01, Vol.106 (2)
Main Authors: Consolino, L., Campa, A., Ravaro, M., Mazzotti, D., Vitiello, M. S., Bartalini, S., De Natale, P.
Format: Article
Language:English
Subjects:
ABSORPTION
ABSORPTION SPECTROSCOPY
Absorptivity
ACCURACY
Applied physics
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
Continuous radiation
Dependence
DOPPLER EFFECT
Electrons
EMISSION
Emission analysis
Gas pressure
IMPLEMENTATION
LASERS
METHANOL
Quantum cascade lasers
RESOLUTION
SATURATION
Spectrometers
Spectrum analysis
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Summary:We report on the evidence of saturation effects in a rotational transition of CH3OH around 2.5 THz, induced by a free-running continuous-wave quantum cascade laser (QCL). The QCL emission is used for direct-absorption spectroscopy experiments, allowing to study the dependence of the absorption coefficient on gas pressure and laser intensity. A saturation intensity of 25 μW/mm2, for a gas pressure of 17 μbar, is measured. This result represents the initial step towards the implementation of a QCL-based high-resolution sub-Doppler THz spectroscopy, which is expected to improve by orders of magnitude the precision of THz spectrometers.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.4905872