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 μm. 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-based materials 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 reflecting metal 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 μm 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 μm flip-chip SDLs are discussed.