1. Direct observation of terahertz frequency comb generationin difference-frequency quantum cascade lasers
- Author
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Consolino, Luigi, Nafa, Malik, De Regis, Michele, Cappelli, Francesco, Bartalini, Saverio, Ito, Akio, Hitaka, Masahiro, Dougakiuchi, Tatsuo, Edamura, Tadataka, De Natale, Paolo, and Fujita, Kazuue
- Subjects
Physics - Optics - 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.
- Published
- 2021
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