Abstract-Frequency and power stabilization of a terahertz quantum-cascade laser using near-infrared optical excitation

T. Alam, M. Wienold, X. Lü, K. Biermann, L. Schrottke, H. T. Grahn, and H.-W. Hübers

 The schematic diagram of the setup used to stabilize the frequency and output power. The QCL is operated in a mechanical cryocooler. The combination of the absorption cell and the Ge:Ga detector A is used to lock the frequency, and the second Ge:Ga detector B is used as a reference for the output power stabilization. (b) Rear-facet illumination with a low-NA single-mode fiber.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-25-36846

We demonstrate a technique to simultaneously stabilize the frequency and output power of a terahertz quantum-cascade laser (QCL). This technique exploits frequency and power variations upon near-infrared illumination of the QCL with a diode laser. It does not require an external terahertz optical modulator. By locking the frequency to a molecular absorption line, we obtain a long-term (one-hour) linewidth of 260 kHz (full width at half maximum) and a root-mean-square power stability below 0.03%. With respect to the free-running case, this stabilization scheme improves the frequency stability by nearly two orders of magnitude and the power stability by a factor of three.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement