Frequency Locking and Monitoring Based on Bi-directional Terahertz Radiation of a 3rd-Order Distributed Feedback Quantum Cascade Laser

• Published in: Journal of infrared, millimeter and terahertz waves Vol. 36; no. 12; pp. 1210 - 1220
• Main Authors: van Marrewijk, N., Mirzaei, B., Hayton, D., Gao, J. R., Kao, T. Y., Hu, Q., Reno, J. L.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.12.2015; Springer Nature B.V; Springer
• Subjects: CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Classical Electrodynamics; Detectors; Electrical Engineering; Electronics and Microelectronics; Engineering; far infrared or terahertz; Feedback; Frequency locking; Frequency stabilization; heterodyne; Instrumentation; linewidth; Quantum cascade lasers; quantum cascade lasers (QCLs); semiconductor lasers, quantum cascades; terahertz; third-order distributed feedback; Frequency locking; Terahertz; Third-order distributed feedback; Quantum cascade lasers (QCLs)
• ISSN: 1866-6892; 1866-6906
• DOI: 10.1007/s10762-015-0210-4

We have performed frequency locking of a dual, forward reverse emitting third-order distributed feedback quantum cascade laser (QCL) at 3.5 THz. By using both directions of THz emission in combination with two gas cells and two power detectors, we can for the first time perform frequency stabilization, while monitor the frequency locking quality independently. We also characterize how the use of a less sensitive pyroelectric detector can influence the quality of frequency locking, illustrating experimentally that the sensitivity of the detectors is crucial. Using both directions of terahertz (THz) radiation has a particular advantage for the application of a QCL as a local oscillator, where radiation from one side can be used for frequency/phase stabilization, leaving the other side to be fully utilized as a local oscillator to pump a mixer.