Progress towards high power, high brightness microchip lasers : multi-watt operation using diamond heatspreaders

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.EThOS - Electronic Theses Online ServiceGBUnited Kingdo