Single frequency vertical external cavity surface emitting lasers

The thesis presents the development and implementation of single frequency vertical external cavity surface emitting lasers (VECSELs). Numerous cavity designs are reported, exploiting some uniqtie features for single frequency operation. A small VECSEL cavity configuration is reported utilising a positive curvature mirror in reverse to create a'6mm cavity where the air gap between the mirror surface and VECSEL wafer act as an etalon, which induces single frequency operation. A 7nm tuning range has been shown with maximum output of 19.4mW. Thermal modelling was undertaken to analyse how the removal of the VECSEL's substrate could increase the thermal efficiency for high power operation. Another small cavity design of length 50mm was created, producing a high power, compact single frequency VECSEL. Using a birefringent filter and solid etalon single frequency operation was achieved. A tuning range oflOnm was achieved with output powers of 271mW. Extensive mapping of the pump profile and eventual manipulation of this resulted in the M2 of the laser of 1.1 being reduced to 1.02. In addition an air etalon system was constructed .to eliminate walk-off losses experienced by the solid etalon. This resulted in a 20nm tuning range. Frequency doubling of an 850nm VECSEL using KNb03 is reported with 1.3mW of 425nm being achieved, corresponding to an efficiency of 3.2%/W. This system also incorporates a polarisation coupled pump system delivering JW at 670nm from a IOO~lm fibre. The relationship between the VECSEL's gain and frequency conversion efficiency is also analysed in detail.EThOS - Electronic Theses Online ServiceGBUnited Kingdo