High peak power gain-switched flared waveguide lasers

Abstract

Summary form only given. Record (14.5 W) peak powers and pulse energies of 490 pJ from a gain-switched flared waveguide quantum-well laser are presented in this paper. Because of their compactness, reliability, efficiency, and relatively low cost, semiconductor lasers are attractive sources of picosecond optical pulses of high peak power. The flared waveguide expands the optical mode from a narrow region which gives a single lateral optical mode, to a wider multimode region for higher power. Flared laser amplifiers have previously been used for mode-locking, Q- and gain-switching of diode lasers. Flared structures have also been utilized for post-amplification to achieve high peak power. Gain-switching offers a considerable advantage in terms of simplicity over mode-locking, in that no resonant cavity is required to be synchronous with the electrical drive, while the external amplifier approach requires additional alignments. High single-mode peak powers have also been obtained from bulk single-heterostructure lasers with ion implanted saturable absorbers. In this work, we gain-switch a flared waveguide laser with a reverse-biased saturable absorber section to obtain high peak powers and pulse energies from a single laser diode without post-amplification. Numerical simulations based on a microscopic laser model verify the effectiveness of the saturable absorber in the generation of high peak power, single-pulse output. Insight obtained from the model suggests that the quantum-confined Stark effect is primarily responsible for saturable absorber operation.