Heterodyne Spectroscopy of Frequency Instabilities in Terahertz Quantum-Cascade Lasers Induced by Optical Feedback

We study the influence of optical feedback on the frequency stability of terahertz (THz) quantum-cascade lasers (QCLs) by high-resolution heterodyne spectroscopy. The emission from two pairs of QCLs operating either at 3.4 or at 4.7 THz is mixed in a Schottky diode and the resulting difference frequ...

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Bibliographic Details
Published inIEEE journal of selected topics in quantum electronics Vol. 23; no. 4; pp. 1 - 6
Main Authors Hubers, Heinz-Wilhelm, Richter, Heiko, Eichholz, Rene, Wienold, Martin, Biermann, Klaus, Schrottke, Lutz, Grahn, Holger T.
Format Journal Article
LanguageEnglish
Published IEEE 01.07.2017
Subjects
Cavity resonators
heterodyne
Laser beams
Laser feedback
Optical feedback
Power lasers
Quantum cascade lasers
Quantum-cascade laser
Spectroscopy
terahertz
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Summary:We study the influence of optical feedback on the frequency stability of terahertz (THz) quantum-cascade lasers (QCLs) by high-resolution heterodyne spectroscopy. The emission from two pairs of QCLs operating either at 3.4 or at 4.7 THz is mixed in a Schottky diode and the resulting difference frequency in the gigahertz range is measured. The high spectral resolution of less than 1 MHz and a time resolution of 1 ms enable us to investigate feedback-induced frequency instabilities on scales that are relevant for spectroscopy. Frequency changes of up to 70 MHz are observed with an optical feedback of only 3 × 10 -5 of the output power of the QCL.
ISSN:1077-260X
1558-4542
DOI:10.1109/JSTQE.2017.2684078