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.

Schottky diodes

frequency stabilization

heterodyne receivers

phase-locked loops

Harmonic mixers

terahertz

Author

Heiko Richter

German Aerospace Center (DLR)

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. 14 3 346-353

Areas 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

More information

Latest update

8/26/2024