Thermal Management in Long-Wavelength Flip-Chip Semiconductor Disk Lasers

We address the thermal management of flip-chip semiconductor disk lasers (SDLs) emitting at wavelengths 1.3-1.6 mu m. The emphasis of the study is on fabricating thin SDL structures with high thermal conductance. An essential part of this task is to use GaAs-basedmaterials in the distributed Bragg reflector (DBR), because they can provide a combination of high thermal conductivity and high refractive index contrast. Furthermore, the reflectivity of the GaAs-based DBR should preferably be enhanced using a thin dielectric layer and a highly reflectingmetal layer. Such a configuration enables very thin mirror structures with a reduced number of DBR layer pairs without compromising the reflectivity. The concept is demonstrated experimentally with a 1.32-mu m flip-chip SDL, where the GaAs-based DBR is finished with a thin Al2O3 layer and a highly reflective Al layer. In addition, the design principles, thermal management, and the development issues related to semiconductor-dielectric-metal mirrors in 1.3-1.6-mu m flip-chip SDLs are discussed.