Concept and analysis of lifetime-switching in pulsed semiconductor lasers

Abstract

Generating short and strong pulses in solid-state lasers is usually achieved with Q-switching, whereby the quality of the laser cavity is switched from a low-quality value, used during a time interval for pumping, to a high-quality value, used to initiate short-pulse emission. The pumping time interval is long so that large population inversion can be achieved. This method does not work for semiconductor lasers, owing to the fast radiative and non-radiative recombination time. We propose the method of lifetime switching (L-switching), which is analogous to Q-switching, but solves the problem of fast recombination during the pump phase. L-switching is achieved via an externally applied electric field (capacitive storage). We introduce the concept and illustrate its functionality by numerically evaluating the system's electrostatic properties, using non-polar InGaN as an example. We address the simultaneous requirements of large lifetime reduction and optical gain, and the effect that excitation-induced screening has on these requirements. The corresponding laser dynamics will be discussed in a future publication.