We have optimized a resonant gain structure of a 920 nm vertical external cavity surface emitting laser. We found that a long saturated carrier lifetime in shallow quantum well (QW) under a high injection level restricts the laser performance. An insertion of non-absorbing laser in the middle of barrier layers with multi QWs is effective to reduce the saturated carrier lifetime and, therefore, to enhance the laser performance. With the optimized laser structure, which has 10 periods of triple In0.09Ga0.91 As QWs located at the anti-standing wave optical field with Al0.3Ga0.7As non-absorbing layers in the middle of GaAs barrier, we achieved 4.9 W operation at 920nm. Subsequently blue laser was achieved by employing an intra-cavity frequency doubling crystal LBO. As a result, we demonstrated 2 W single transverse mode operation in blue (460 nm) with a 20 W pump laser power. The conversion efficiency from 808 nm pump laser to the blue laser is measured to be 10 %.
We report on a 1060 nm single transverse mode operation of an end-pumped vertical external cavity surface emitting laser (VECSEL). End-pumping scheme is enabled by capillary bonding of a VECSEL chip with a diamond heat spreader followed by a GaAs substrate removal by selective wet etching. The VECSEL structure is consisted of 10 periods of resonant periodic gain with an 8 nm InGaAs single quantum well at the antinodes of the standing wave optical field and a 35 pair AlAs/AlGaAs bottom distributed Brag reflector (DBR). Optical pump efficiency through the bottom mirror is enhanced by a modified DBR structure with a reduced reflectance in 808 nm pump wavelength region. A low threshold pump density of 433 W/cm2 and over 45 W/W optical to optical conversion efficiency are achieved with reflectivity of 94 % output coupler at the heat spreader temperature of 20°C. The laser operates in a circular TEM00 mode (M2<1.5) up to 7 W, and maximum power of 9.1 W is limited by our pump laser power.