Opt. Lett. 39, 3962–3965 (2014)

Quantum cascade lasers are a convenient source of radiation in the terahertz frequency range of the electromagnetic spectrum. Now, Y. Halioua and co-workers from the University of Leeds and the Université de Paris-Sud have reported a device that exhibits extremely low beam divergence and a high output peak power of 17 mW. This was achieved by incorporating a novel type of photonic crystal (PC) design and ensuring that the device only operates on the PC's radiative modes. The use of PC structures offers the benefits of tight optical confinement and ultra-high cavity Q-factors as well as the possibility to control the emitted mode pattern and beam shape. Previously, power was limited by the competition between non-radiative and radiative modes of the PC structure, which can constructively or destructively interfere. The researchers assert that even higher output powers should be possible by increasing the lateral size of the resonator.