Engineering vertical emission in THz quantum cascade lasers

摘要

Surface emission from distributed feedback terahertz quantum cascade lasers operating in double-metal waveguides is investigated. After analyzing the origin of vertical out-coupling in linear second-order gratings, the enhancement of radiative efficiency achieved with quasi-periodic and circular gratings is presented. Linear Fibonacci resonators and microdisk lasers have been realized allowing great flexibility in tailoring the surface emission intensity and profile. Finally, ring lasers showing high power collimated emission in the vertical direction by employing a double-slit grating configuration will be discussed.