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arXiv · 2103.09768

Direct observation of terahertz frequency comb generationin difference-frequency quantum cascade lasers

Luigi Consolino·Malik Nafa·Michele De Regis·Francesco Cappelli·Saverio Bartalini·Akio Ito·Masahiro Hitaka·Tatsuo Dougakiuchi·Tadataka Edamura·Paolo De Natale·Kazuue Fujita
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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.

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Luigi Consolino, Malik Nafa, Michele De Regis, Francesco Cappelli, Saverio Bartalini, Akio Ito, Masahiro Hitaka, Tatsuo Dougakiuchi, Tadataka Edamura, Paolo De Natale, Kazuue Fujita. 2021-03-17. Direct observation of terahertz frequency comb generationin difference-frequency quantum cascade lasers. https://doi.org/10.3390/app11041416

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