Surface-Emitting Broadband THz Quantum Cascade Laser Frequency Combs with Inverse-Designed Waveguide Facets

THz Quantum Cascade Lasers are unipolar electrically driven semiconductor lasers that can also operate as frequency combs for broadband metrology and sensing [1], [2]. THz quantum cascade lasers are usually processed in double metal waveguide ridges exhibiting low slope efficiencies and a patterned far field [3]. Surrounding the ridge structure with the low-loss polymer Benzocyclobuten (BCB) allows for an extended top contact improving waveguide and thermal properties as well as permitting the implementation of passive structures [4].