Phase Locking of Quantum-Cascade Lasers Operating Around 3.5 and 4.7 THz With a Schottky-Diode Harmonic MixerShow others and affiliations
2024 (English)In: IEEE Transactions on Terahertz Science and Technology, ISSN 2156-342X, E-ISSN 2156-3446, Vol. 14, no 3, p. 346-353Article in journal (Refereed) Published
Abstract [en]
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 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.
Place, publisher, year, edition, pages
IEEE Microwave Theory and Techniques Society , 2024. Vol. 14, no 3, p. 346-353
Keywords [en]
Diodes; Harmonic analysis; Heterodyning; Laser mode locking; Linewidth; Locks (fasteners); Mode-locked fiber lasers; Quantum cascade lasers; Schottky barrier diodes; Spectrometers; Temperature measurement; Critical component; Frequency measurements; Frequency stabilization; Harmonic mixers; Heterodyne receivers; High resolution; Phase-locking; Schottky diodes; Tera Hertz; Tuning; Natural frequencies
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:ri:diva-73327DOI: 10.1109/TTHZ.2024.3385379Scopus ID: 2-s2.0-85190167201OAI: oai:DiVA.org:ri-73327DiVA, id: diva2:1864633
2024-06-032024-06-032024-06-03Bibliographically approved