Frequency Stabilization of a Single Mode Terahertz Quantum Cascade Laser to the Kilohertz Level

A simple analog locking circuit was shown to stabilize the beat signal between a 2.408 THz quantum cascade laser and a CH2DOH THz CO2 optically pumped molecular laser to 3-4 kHz (FWHM). This is approximately a tenth of the observed long-term (t ~ sec) linewidth of the optically pumped laser showing that the feedback loop corrects for much of the mechanical and acoustic-induced frequency jitter of the gas laser. The achieved stability should be sufficient to enable the use of THz quantum cascade lasers as transmitters in short-range coherent transceivers.
Published in Optics Express, v17 n9, 27 April 2009.