title: Common mode frequency instability in internally phase-locked terahertz quantum cascade lasers.
abstract: 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.
authors: Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185, USA. mcwanke@sandia.gov
authors: M C
authors: MC
authors: Wanke
authors: A D
authors: AD
authors: Grine
authors: C T
authors: CT
authors: Fuller
authors: C D
authors: CD
authors: Nordquist
authors: M J
authors: MJ
authors: Cich
authors: J L
authors: JL
authors: Reno
authors: Mark
authors: M
authors: Lee
mesh_terms: D016477:Artifacts; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007834:Lasers; D009991:Oscillometry / Q000295:instrumentation* / Q000379:methods*