Direct Observation of Terahertz Frequency Comb Generation in Difference-Frequency Quantum Cascade Lasers
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 nee...
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Veröffentlicht in: | Applied sciences 2021-02, Vol.11 (4), p.1416, Article 1416 |
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Sprache: | eng |
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Zusammenfassung: | 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 lambda = 6.5 mu m and a Fabry-Perot device at around lambda = 6.9 mu m. The resulting ultra-broadband THz emission extends from 1.8 to 3.3 THz, with a total output power of 8 mu 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. |
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ISSN: | 2076-3417 2076-3417 |
DOI: | 10.3390/app11041416 |