Tailoring Quantum Dot Saturable Absorber Mirrors for Ultra-Short Pulse Generation

ABSTRACTWe have designed and grown a series of quantum dot semiconductor saturable absorber mirrors (QD-SESAMs) for a range of operating wavelengths, incorporating innovative design and processing features to optimise the device performance. Using a range of reflectivity studies, ellipsometric measurements and both time-integrated and time-resolved spectroscopic studies, we have conducted detailed investigations of device performance. Extensive modelling work of dielectric multilayers has been undertaken which supports our experimental findings and allows us to understand and design novel structures in order to improve and tailor device characteristics, including dielectric capping and non-normal incidence. We demonstrate samples designed for operation with the higher excited-states of the QDs which produced a self-starting train of mode-locked pulses with a temporal duration of 200 ps at a repetition rate of 78 MHz in a Nd:YVO4 solid-state laser. We also present SESAMs incorporating electronically coupled QD bilayers, allowing long wavelength operation.