Non-linear lensing in optically-pumped semiconductor lasers

Optically pumped semiconductor lasers (OPSLs) are a versatile family of lasers offering wavelength flexibility, high beam quality and multi-Watt level output powers. SESAM modelocked OPSLs can produce near transform limited femtosecond pulses at Gigahertz repetition rates. The performance of modelocked OPSLs is limited by the speed of the response of the SESAM and its resistance to damage. This thesis explores the potential for SESAM-free modelocking of OPSLs through the utilisation of a non-linear lens in the semiconductor gain structure.The thesis presents two strands of research: experimental and computational. The nonlinear lens is measured using a reflection z-scan technique. A computational model of a modelocked OPSL is developed to explore the transient dynamics of lasing onset and to test the temporal stability of the modelocked pulse. This thesis demonstrates that understanding the nature of the non-linear lens unlocks the potential to explore the possibility of improving laser performance in modelocked OPSLs.