Open AccessCommon mode frequency instability in internally phase-locked terahertz quantum cascade lasers
Author(s) -
Michael Clement Wanke,
Albert D. Grine,
Charles T. Fuller,
Christopher Nordquist,
Michael Joseph Cich,
John L. Reno,
Mark Lee
Publication year - 2011
Publication title -
optics express
Language(s) - Uncategorized
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.19.024810
Subject(s) - laser linewidth , optics , quantum cascade laser , terahertz radiation , cascade , laser , semiconductor laser theory , physics , phase noise , bandwidth (computing) , longitudinal mode , diode , materials science , optoelectronics , telecommunications , chemistry , chromatography , computer science
Feedback from a diode mixer integrated into a 2.8 THz quantum cascade laser (QCL) was used to phase lock the difference frequencies (DFs) among the Fabry-Perot (F-P) longitudinal modes of a QCL. Approximately 40% of the DF power was phase locked, consistent with feedback loop bandwidth of 10 kHz and phase noise bandwidth ~0.5 MHz. While the locked DF signal has ≤ 1 Hz linewidth and negligible drift over ~30 min, mixing measurements between two QCLs and between a QCL and molecular gas laser show that the common mode frequency stability is no better than a free-running QCL.