Open AccessInvestigation of spectral gain narrowing in quantum cascade lasers using terahertz time domain spectroscopy
Author(s) -
Nathan Jukam,
Sukhdeep Dhillon,
Dimitri Oustinov,
Zhenyu Zhao,
Sophie Hameau,
J. Tig,
S. Barbieri,
Angela Vasanelli,
P. Filloux,
Carlo Sirtori,
X. Marcadet
Publication year - 2008
Publication title -
applied physics letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 442
eISSN - 1077-3118
pISSN - 0003-6951
DOI - 10.1063/1.2979682
Subject(s) - lasing threshold , terahertz radiation , full width at half maximum , terahertz time domain spectroscopy , laser , cascade , spectroscopy , spectral width , optoelectronics , terahertz spectroscopy and technology , optics , gain switching , physics , semiconductor laser theory , quantum cascade laser , materials science , chemistry , chromatography , quantum mechanics
The spectral gain of bound-to-continuum terahertz quantum cascade lasers (QCLs) is measured as a function of current density using terahertz time-domain spectroscopy. During lasing action the full width at half maximum (FWHM) of the gain is found to monotonically decrease with increasing current density until lasing action stops at which point the FWHM reaches a minimum (0.22 THz for a laser operating at 2.1 THz). Band structure calculations show that the spectral gain narrowing is due to the alignment and misalignment of the injector with the active region as a function of the applied bias field.
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