Dynamics of ultra-broadband terahertz quantum cascade lasers for comb operation | Zendy

Hua Li | Zendy; Pierre Laffaille | Zendy; Djamal Gacemi | Zendy; Marc Apfel | Zendy; Carlo Sirtori | Zendy; Jeremie Leonardon | Zendy; G. Santarelli | Zendy; Markus Rösch | Zendy; Giacomo Scalari | Zendy; Mattias Beck | Zendy; Jérôme Faist | Zendy; W. Hänsel | Zendy; Ronald Holzwarth | Zendy; S. Barbieri | Zendy

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Dynamics of ultra-broadband terahertz quantum cascade lasers for comb operation

Author(s) -

Hua Li,

Pierre Laffaille,

Djamal Gacemi,

Marc Apfel,

Carlo Sirtori,

Jeremie Leonardon,

G. Santarelli,

Markus Rösch,

Giacomo Scalari,

Mattias Beck,

Jérôme Faist,

W. Hänsel,

Ronald Holzwarth,

S. Barbieri

Publication year - 2015

Publication title -

optics express

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 1.394

H-Index - 271

ISSN - 1094-4087

DOI - 10.1364/oe.23.033270

Subject(s) - physics , laser , terahertz radiation , optics , lasing threshold , beat (acoustics) , cascade , semiconductor laser theory , coherence (philosophical gambling strategy) , quantum noise , optoelectronics , quantum , chemistry , chromatography , quantum mechanics

We present an experimental investigation of the multimode dynamics and the coherence of terahertz quantum cascade lasers emitting over a spectral bandwidth of ~1THz. The devices are studied in free-running and under direct RF modulation. Depending on the pump current we observe different regimes of operation, where RF spectra displaying single and multiple narrow beat-note signals alternate with spectra showing a single beat-note characterized by an intense phase-noise, extending over a bandwidth up to a few GHz. We investigate the relation between this phase-noise and the dynamics of the THz modes through the electro-optic sampling of the laser emission. We find that when the phase-noise is large, the laser operates in an unstable regime where the lasing modes are incoherent. Under RF modulation of the laser current such instability can be suppressed and the modes coherence recovered, while, simultaneously, generating a strong broadening of the THz emission spectrum.

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