Scientific Results

Quantum-limited frequency fluctuations in a terahertz laser

Year: 2012

Authors: Vitiello M.S., Consolino L., Bartalini S., Taschin A., Tredicucci A., Inguscio M., De Natale P.

Autors Affiliation: CNR- Istituto Nazionale di Ottica and LENS (European Laboratory for Non-linear Spectroscopy), Via Carrara 1, 50019 Sesto Fiorentino (FI), Italy;
NEST, CNR – Istituto Nanoscienze and Scuola Normale Superiore, Piazza San Silvestro 12, 56127, Pisa, Italy;
Dipartimento di Fisica e Astronomia, Universita` degli Studi di Firenze, Via Carrara 1, 50019 Sesto Fiorentino (FI), Italy

Abstract: Quantum cascade lasers can be considered the primary achievement of electronic band structure engineering, showing how artificial materials can be created through quantum design to have tailor-made properties that are otherwise non-existent in nature. Indeed, quantum cascade lasers can be used as powerful testing grounds of the fundamental physical parameters determined by their quantum nature, including the intrinsic linewidth of laser emission, which in such lasers is significantly affected by the optical and thermal photon number generated in the laser cavity. Here, we report experimental evidence of linewidth values approaching the quantum limit in far-infrared quantum cascade lasers. Despite the broadening induced by thermal photons, the measured linewidth results narrower than that found in any other semiconductor laser to date. By performing noise measurements with unprecedented sensitivity levels, we highlight the key role of gain medium engineering and demonstrate that properly designed semiconductor-heterostructure lasers can unveil the mechanisms underlying the laser-intrinsic phase noise, revealing the link between device properties and the quantum-limited linewidth.

Journal/Review: NATURE PHOTONICS

Volume: 6 (8)      Pages from: 525  to: 528

More Information: This work was partly supported by the Italian Ministry of Education, University, and Research (MIUR) through the programme \’FIRB-Futuro in Ricerca 2010 RBFR10LULP Fundamental Research on Terahertz Photonic Devices\’ and by the Ente Cassa di Risparmio di Firenze and Regione Toscana, through project CTOTUS, in the framework of POR-CReO FESR 2007-2013. The authors thank H.E. Beere and D.A. Ritchie for the growth of the QCL structure, J.H. Xu for technical support and J. Faist for useful discussions.
KeyWords: Quantum cascade lasers; Cascade lasers; Intrinsic linewidth; Narrow-linewidth; Room-temperature
DOI: 10.1038/nphoton.2012.145

Citations: 103
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English