Direct observation of terahertz frequency comb generationin difference-frequency quantum cascade lasers
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, beingthe only electrically pumped device able to operate in the 0.6-6 THz range without the need of bulky andexpensive liquid helium cooling. Here we present comb operation obtained by intra-cavity mixing of adistributed feedback laser at {\lambda} = 6.5 {\mu}m and a Fabry-P\'erot device at around {\lambda} = 6.9 {\mu}m. The resultingultra-broadband THz emission extends from 1.8 to 3.3 THz, with a total output power of 8 {\mu}W at 78K.The THz emission has been characterized by multi-heterodyne detection with a primary frequencystandard 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 MHzaccuracy. In the next future this setup can be used for Fourier transform based evaluation of the phaserelation among the emitted THz modes, paving the way to room-temperature, compact and field-deployable metrological grade THz frequency combs.
Cite
@article{arxiv.2103.09768,
title = {Direct observation of terahertz frequency comb generationin difference-frequency quantum cascade lasers},
author = {Luigi Consolino and Malik Nafa and Michele De Regis and Francesco Cappelli and Saverio Bartalini and Akio Ito and Masahiro Hitaka and Tatsuo Dougakiuchi and Tadataka Edamura and Paolo De Natale and Kazuue Fujita},
journal= {arXiv preprint arXiv:2103.09768},
year = {2021}
}