Towards high power flip-chip long-wavelength semiconductor disk lasers

Optically pumped semiconductor disk lasers (SDLs) are presented with emphasis on wafer bonding InP-based active regions with GaAs-based distributed Bragg reflectors (DBRs) and reducing the number of required layer pairs in the DBR. The wafer bonding is performed at a relatively low temperature of 200 °C utilizing transparent intermediate bonding layers. The reflectivity of the semiconductor DBR section is enhanced by finishing the DBR with a thin low refractive index layer and a highly reflecting metal layer. Such a design enables considerably thinner mirror structures than the conventional design, where the semiconductor DBR is finished with mere metal layers. In addition, a 90 nm thick Al2O3 layer is shown to produce negligible increase in the thermal resistance of the SDL. Furthermore, a flip-chip SDL with a GaAs/AlAs-Al2O3-Al mirror is demonstrated with watt-level output power at the wavelength of 1.32 μm. The properties and future improvement issues for flip-chip SDLs emitting at 1.3–1.6 μm are also discussed.