Spectral purity and tunability of terahertz quantum cascade laser sources based on intracavity difference-frequency generation

Year: 2017

Authors: Consolino L., Jung S., Campa A., De Regis M., Pal S., Kim J.H., Fujita K., Ito A., Hitaka M., Bartalini S., De Natale P., Belkin M.A., Vitiello M.S.

Autors Affiliation: Consiglio Nazionale delle Ricerche (CNR)–Istituto Nazionale di Ottica and European Laboratory for Non-Linear Spectroscopy, Via Carrara 1, 50019 Sesto Fiorentino (Firenze), Italy; Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712, USA; National Enterprise for nanoScience and nanoTechnology (NEST), CNR–Istituto Nanoscienze and Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy; Central Research Laboratory, Hamamatsu Photonics K.K., Hamakita-ku, Hamamatsu 434-8601, Japan

Abstract: Terahertz sources based on intracavity difference-frequency generation in mid-infrared quantum cascade lasers (THz DFG-QCLs) have recently emerged as the first monolithic electrically pumped semiconductor sources capable of operating at room temperature across the 1- to 6-THz range. Despite tremendous progress in power output, which now exceeds 1 mW in pulsed and 10 mW in continuous-wave regimes at room temperature, knowledge of the major figure of merits of these devices for high-precision spectroscopy, such as spectral purity and absolute frequency tunability, is still lacking. By exploiting a metrological grade system comprising a terahertz frequency comb synthesizer, we measure, for the first time, the free-running emission linewidth (LW), the tuning characteristics, and the absolute center frequency of individual emission lines of these sources with an uncertainty of 4 x 10(-10). The unveiled emission LW (400 kHz at 1-ms integration time) indicates that DFG-QCLs are well suited to operate as local oscillators and to be used for a variety of metrological, spectroscopic, communication, and imaging applications that require narrow-LW THz sources.


Volume: 3 (9)      Pages from: e1603317-1  to: e1603317-8

KeyWords: Linewidth enhancement factor; Room-temperature; Continuous-wave; Phase-locking; Noise; Pumping (laser); Quantum cascade lasers; Semiconductor lasers, Difference-frequency generation; Electrically pumped; High-precision spectroscopy; Imaging applications; Mid-infrared quantum cascade; Semiconductor sources; Terahertz frequencies; Terahertz quantum-cascade lasers, Optical frequency conversion
DOI: 10.1126/sciadv.1603317

Citations: 30
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