Phase-Locking of Quantum-Cascade Lasers Operating Around 3.5 THz and 4.7 THz with a Schottky-Diode Harmonic Mixer
Journal article, 2024
Quantum-cascade lasers (QCLs) are critical components for high-resolution terahertz spectroscopy, especially in heterodyne spectrometers, where they serve as local oscillators. For this purpose, QCLs with stable frequencies and narrow linewidths are essential since their spectral properties limit the spectral resolution. We demonstrate the phase-locking of QCLs around 3.5 THz and 4.7 THz in mechanical cryocoolers. These frequencies are particularly interesting for atmospheric research because they correspond to the hydroxyl radical and the neutral oxygen atom. The phase-locked loop is based on frequency mixing of the QCLs at 3.5 and 4.7 THz with the sixth and eighth harmonic, respectively, generated by an amplifier-multiplier chain operating around 600 GHz, with a Schottky diode harmonic mixer. At both frequencies we achieved a linewidth of the intermediate frequency signal of less than 1 Hz. This is about seven orders of magnitude less than the linewidth of the free running QCL.
terahertz
phase-locked loops
Schottky diodes
heterodyne receivers
Harmonic mixers
frequency stabilization
Author
Heiko Richter
Nick Rothbart
German Aerospace Center (DLR)
Martin Wienold
German Aerospace Center (DLR)
Xiang Lü
Paul Drude Institut fur Festkorperelektronik
Klaus Biermann
Paul Drude Institut fur Festkorperelektronik
Lutz Schrottke
Paul Drude Institut fur Festkorperelektronik
Divya Jayasankar
Chalmers, Microtechnology and Nanoscience (MC2), Terahertz and Millimetre Wave Laboratory
Jan Stake
Chalmers, Microtechnology and Nanoscience (MC2), Terahertz and Millimetre Wave Laboratory
Peter Sobis
Chalmers, Microtechnology and Nanoscience (MC2), Terahertz and Millimetre Wave Laboratory
Heinz-Wilhelm Hübers
German Aerospace Center (DLR)
IEEE Transactions on Terahertz Science and Technology
2156-342X (ISSN) 21563446 (eISSN)
Vol. in PressAreas of Advance
Information and Communication Technology
Infrastructure
Kollberg Laboratory
Nanofabrication Laboratory
Subject Categories
Electrical Engineering, Electronic Engineering, Information Engineering
Other Electrical Engineering, Electronic Engineering, Information Engineering
DOI
10.1109/TTHZ.2024.3385379