Vertical external-cavity surface-emitting laser based on a novel GaInP/AlGaInP grating waveguide for efficient high-power operation

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Power scaling with versatile semiconductor disk lasers is still a challenge, especially for the red spectral region with the GaInP/AlGaInP material system. The gain structure is quite sensitive to temperature effects and requires intra-cavity cooling to bypass the thick, poorly heat-conducting DBR mirror. Reducing the heat load by in-well pumping has been shown to be very effective. However, when used in combination with intra-cavity cooling, external complex multi-pass optics with many passes for efficient pump-radiation absorption is needed.Our objective is to circumvent these limitations by replacing the semiconductor disk with DBR by an active grating waveguide structure (GWS) and – for the first time – to demonstrate a grating-waveguide-based GaInP VECSEL in the red spectral range. Therefore, the grating waveguide should have the following characteristics:– highly reflective for the laser mode and efficient for coupling of the pump radiation,– enhanced gain at the laser transition and enhanced absorptance of the pump radiation,– heatsink outside the resonator, but close to the QW/QD layers, for effective cooling.There are several options to realize these requirements with various trade-offs, eg. high-contrast gratings or weakly coupled resonant waveguide gratings. Different polarization states and/or wavelengths can be addressed with two-dimensional gratings (photonic crystals). Since this is quite new territory, we will explore the most promising designs in several consecutive steps with feedback loops between design, modeling, technology (epitaxy, grating fabrication), and experiment (spectroscopic and laser characterization):– Highly reflective passive devices,– QW or QD containing active devices, and– A fully functional laser structure (GWS VECSEL), bonded to a diamond heat spreader.