Mode-locked surface emitting semiconductor lasers

Abstract

Optically-Pumped Vertical External Cavity Surface Emitting Lasers (OP-VECSELs) arc novel semiconductor-based lasers that have many advantages over other lasers in terms of the power scalability, good beam quality, compactness and low cost they can offer. They can be passively mode-locked with a Semiconductor Saturable Absorber Mirror (SESAM) to produce transform-limited sub-300 fs pulses directly from the laser cavity with high repetition rates.
This thesis describes an experimental and theoretical investigation of OP-VECSELs. A full characterization is done on a VECSEL sample to understand time physics behind its operation iii the Continuous Wave (CW) mode and in the mode—locked mode. Then. a numerical model that, for the first time, shows the role of the Optical Stark Effect (OSE) in shaping the mode-locked pulses in the approach to steady state is introduced. TIme model results are broadly consistent with observed behavior of our diode-locked VECSELs.
Here, I also report the first coherent generation and detection of terahertz radiation using all-semiconductor components. Radiation with a bandwidth of 0.8 THz has been generated using sub-500 fs pulses with an average power of 20 mW from a mode-locked VECSEL which contains InGaAs quantum wells and an LT-GaAs/InGaAs emitter/receiver antenna in a Terahertz Time Domain Spectrometer (THz-TDS) setup. The first mode locked OP-VECSEL at 830 rim is reported here. The combination of a GaAs quantum well-based gain sample and SESAI\I yielded an output with an average power of 5 mW and 15 ps-long pulses at a repetition rate of 1.9 GHz. A pumping module used to drive the laser was built for this purpose by combining the output of two commercial 665 nm diode lasers.

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