Direct Observation of Terahertz Frequency Comb Generation in Difference-Frequency Quantum Cascade Lasers

Year: 2021

Authors: Consolino L., Nafa M., De Regis M., Cappelli F., Bartalini S., Ito A., Hitaka M., Dougakiuchi T., Edamura T., De Natale P., Fujita K.

Autors Affiliation: CNR, Ist Nazl Ott, Via N Carrara 1, I-50019 Sesto Fiorentino, Italy;LENS, Via N Carrara 1, I-50019 Sesto Fiorentino, Italy; Hamamatsu Photon KK, Cent Res Lab, Hamakita Ku, 5000 Hirakuchi, Hamamatsu, Shizuoka 4348601, Japan

Abstract: Terahertz quantum cascade laser sources based on intra-cavity difference frequency generation from mid-IR devices are an important asset for applications in rotational molecular spectroscopy and sensing, being the only electrically pumped device able to operate in the 0.6-6 THz range without the need of bulky and expensive liquid helium cooling. Here we present comb operation obtained by intra-cavity mixing of a distributed feedback laser at ? = 6.5 ?m and a Fabry-Pérot device at around ? = 6.9 ?m. The resulting ultra-broadband THz emission extends from 1.8 to 3.3 THz, with a total output power of 8 ?W at 78 K. The THz emission has been characterized by multi-heterodyne detection with a primary frequency standard referenced THz comb, obtained by optical rectification of near infrared pulses. The down-converted beatnotes, simultaneously acquired, confirm an equally spaced THz emission down to 1 MHz accuracy. In the future, this setup can be used for Fourier transform based evaluation of the phase relation among the emitted THz modes, paving the way to room-temperature, compact, and field-deployable metrological grade THz frequency combs.

Journal/Review: APPLIED SCIENCES-BASEL

Volume: 11 (4)      Pages from: 1416-1  to: 1416-12

KeyWords: Intracavity difference frequency generation; Quantum cascade lasers: Terahertz lasers
DOI: 10.3390/app11041416

Citations: 5
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