Absorption recovery dynamics in 2µm GaSb-based SESAMs

The interplay between growth and design parameters of GaSb-based quantum-well semiconductor saturable absorber mirrors (SESAMs) and their corresponding absorption recovery time is investigated. The analysis proves an inherently rapid absorption recovery time of GaSb SESAMs operating at a 2 µ m wavelength range, which is surprisingly independent of the growth temperature for a large temperature range from 350 to 530 °C. Moreover, SESAMs incorporating In x Ga 1− x As y Sb 1− y quantum wells exhibit a weak variation of the absorption recovery time with changing indium content and with varying lattice strain. The strongest reduction of the absorption recovery time is observed upon placing the quantum wells in the proximity of the SESAM's top layer, and applying an antireflection coating to enhance the interaction with the optical field. Stable mode-locking of a Tm : YAG laser at 2 µ m is obtained with an antireflection coated sample incorporating a single surface quantum well.