No description available.

No description available.

A detailed optical characterisation of (1.3 )InAs quantum-dot-in-well (DWELL) laser structures, is described.

No description available.

No description available.

The microchip laser – a sub-millimetre thick slice of laser gain material onto which cavity mirrors are directly coated – offers a robust, compact laser design; however, this design both inhibits heat removal and is sensitive to thermally induced distortions. This limits power scaling and degrades beam quality at higher powers. This thesis describes progress towards achieving a high power, high brightness microchip laser using diamond heatspreaders. Diamond, silicon carbide (SiC) and sapphire heatspreaders are examined in a selection of dopeddielectric microchip lasers using finite element analysis (FEA). This suggests that diamond is the heatspreader of choice for most applications. The role of gain material thickness with respect to temperature gradients within Nd:YVO4, Nd:GdVO4 and Yb:KYW microchip lasers incorporating diamond heatspreaders is explored. Operation in the thin-disk regime is predicted to provide improved thermal management. At lower thicknesses, diamond is likely to outperform SiC at reducing thermal lensing and improving the overlap between the pump and fundamental cavity modes. This offers the potential for better beam quality. The same heatspreader materials examined using FEA are also investigated experimentally in extended cavity and quasi-microchip Nd:YVO4 lasers. It is found that diamond gives rise to the best performance. The performance of Nd:GdVO4 and a 1060nm semiconductor disk laser in an extended cavity format incorporating an intra-cavity diamond heatspreader is compared with that of Nd:YVO4. Finally, initial characterisation of a Yb:KYW extended cavity laser is presented. Over 3W of output power is achieved using Nd:YVO4 microchip lasers in novel configurations incorporating intra and extra-cavity diamond heatspreaders. Routes to achieving higher brightness are discussed. Finally, thoughts are given on how to best achieve high brightness, high power microchip lasers in the future by moving to smaller gain thicknesses and using Yb:KYW which is well suited to efficient operation in this configuration.

Vertical External Cavity Surface Emitting Lasers (VECSELs) are an amalgamation of solid state laser and semiconductor laser technologies. They combine the high power and excellent beam quality associated with solid state laser design with the compactness and wavelength flexibility of semiconductor lasers. This thesis will report on the first red VECSEL which was used to demonstrate a novel VECSEL array and the first UV VECSEL using an AlGahiP gain region.

The semiconductor disk laser (SDL) takes advantage of the potential for band-gap engineering in semiconductor multilayers to give a wavelength flexible laser source; the free-space cavity not only gives the freedom of design to achieve good beam quality and power scaling, but also to insert wavelength control elements into the cavity for spectral narrowing and tuning, and for second harmonic generation (SHG). Thermal modelling using finite element analysis (FEA) was used to compare the different thermal management techniques used to dissipate the heat generated by the optical pumping process, which ultimately limits the output power achievable in these devices: an intracavity diamond heatspreader was chosen as the most appropriate technique where wavelength diversity is required.

Semiconductor Disk Lasers (SDLs) are compact lasers suitable for watt to multi-watt direct generation in the 670-2350nm waveband and frequency-doubled operation in the ultraviolet and visible regions. This is, however, critically dependent on the thermal management strategy used as, in this type of laser, the pump is absorbed over micrometer lengths and the gain and loss are temperature sensitive. In this thesis, we compare the two heat dissipation techniques that have been successfully deployed to-date: the "thin device" approach where the semiconductor active mirror is bonded onto a heatsink and its substrate subsequently removed, and the "heatspreader" technique where a high thermal conductivity plalelet is directly bonded onto the active part of the unprocessed epilayer.

No description available.