Simulation of 1550 nm diamond VECSEL with high contrast grating

In the following paper a simulation of optically pumped vertical external cavity surface emitting lasers (VECSEL) with a novel approach for the improvement of the heat management is presented. In recent VECSEL structures, it was common to use one top diamond heat spreader in order to decrease the thermal resistance of the device by redistributing the heat flow to the lateral regions and thus transporting heat down to the copper heat sink more efficiently. We present here further improvement of the heat management by eliminating the bottom DBR from the heat flow path and substituting it for a diamond with a High Contrast Grating (HCG). Hence the active region, which consists of 5 pairs of AlGaInAs quaternary alloy quantum wells, is sandwiched between two diamond heat spreading layers. The structure of Si HCG deposited on a diamond provides broad wavelength range in which reflectivity is close to 100% for the emitted beam for perpendicular mode polarization with respect to the direction of the HCG trenches. The HCG assures less than 20% reflection and near zero absorption of pumping light, hence it allows for on-axis bottom pumping scheme and integration of the VECSEL with the pumping laser. According to the simulations 300 mu m thick top diamond heat spreader is enough to assure effective heat dissipation mechanism. Replacing the bottom DBR with the diamond heat spreader will provide additional 10% reduction of the thermal impedance. The minimum of thermal impedance is achieved for about 450 mu m thick bottom diamond heat spreader.