Abstract-Terahertz quantum-cascade patch-antenna VECSEL with low power dissipation

Applied Physics Letters

Christopher A. Curwen, John L. Reno,  Benjamin S. Williams,

(a) Simulated peak reflectance for a ridge-based (Λ = 50 μm, w = 8.3 μm) and patch-based (Λ = 47 μm, w = 11.45 μm, L = 7.5 μm) metasurface design for a 10 μm thick 4.7 THz active region. Insets show field distribution for the two cases (note: relative strength of fields between the patch and ridge are not to scale).

https://aip.scitation.org/doi/abs/10.1063/5.0008867

We report a terahertz quantum-cascade vertical-external-cavity surface-emitting laser (QC-VECSEL) based upon a metasurface consisting of an array of gain-loaded resonant patch antennas. Compared with the typical ridge-based metasurfaces previously used for QC-VECSELs, the patch antenna surface can be designed with a much sparser fill factor of gain material, which allows for reduced heat dissipation and improved thermal performance. It also exhibits larger amplification thanks to enhanced interaction between the incident radiation and the QC-gain material. We demonstrate devices that produce several milliwatts of continuous-wave power in a single mode at ∼4.6 THz and dissipate less than 1 W of pump power. Use of different output couplers demonstrates the ability to optimize device performance for either high power or high operating temperature. Maximum demonstrated power is 6.7 mW at 4 K (0.67% wall-plug efficiency, WPE) and 0.8 mW at 77 K (0.06% WPE). Directive output beams are measured throughout with divergence angles of ∼5°.

Microfabrication was performed at the UCLA Nanoelectronics Research Facility, electron beam lithography was performed at the California NanoSystems Institute (CNSI) at UCLA, and wire bonding was performed at the UCLA Center for High Frequency Electronics. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solution of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under Contract No. DE-NA-0003525. Partial funding was provided by the National Science Foundation (Nos. 1407711 and 1711892) and National Aeronautics and Space Administration (Nos. NNX16AC73G and 80NSSC19K0700).