Spectroscopic Applications of Terahertz Quantum-Cascade Lasers - Couverture souple

Alam, Tasmim

 
9783736972971: Spectroscopic Applications of Terahertz Quantum-Cascade Lasers
Couverture souple
ISBN 10 : 3736972970 ISBN 13 : 9783736972971
Editeur : Cuvillier, 2020

Synopsis

Quantum cascade lasers (QCLs) are attractive for high-resolution spectroscopy because they can provide high power and a narrow linewidth. They are particularly promising in the terahertz (THz) range since they can be used as local oscillators for heterodyne detection as well as transmitters for direct detection. However, THz QCL-based technologies are still under development and are limited by the lack of frequency tunability as well as the frequency and output power stability for free-running operation. In this dissertation, frequency tuning and linewidth of THz QCLs are studied in detail by using rotational spectroscopic features of molecular species. In molecular spectroscopy, the Doppler eff ect broadens the spectral lines of molecules in the gas phase at thermal equilibrium. Saturated absorption spectroscopy has been performed that allows for sub-Doppler resolution of the spectral features. One possible application is QCL frequency stabilization based on the Lamb dip. Since the tunability of the emission frequency is an essential requirement to use THz QCL for high-resolution spectroscopy, a new method has been developed that relies on near-infrared (NIR) optical excitation of the QCL rear-facet. A wide tuning range has been achieved by using this approach. The scheme is straightforward to implement, and the approach can be readily applied to a large class of THz QCLs. The frequency and output stability of the local oscillator has a direct impact on the performance and consistency of the heterodyne spectroscopy. A technique has been developed for a simultaneous stabilization of the frequency and output power by taking advantage of the frequency and power regulation by NIR excitation. The results presented in this thesis will enable the routine use of THz QCLs for spectroscopic applications in the near future.

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Éditeur
Cuvillier
Date d'édition
2020
Langue
anglais
ISBN 10 
3736972970
ISBN 13 
9783736972971
Reliure
Broché
Nombre de pages
142
Coordonnées du fabricant
info@cuvillier.de
info@cuvillier.de

Nonnenstieg 8
Göttingen
37075
Allemagne