Wavelength tunable red AlGaInP-VECSEL emitting at around 660 nm

Abstract

We present a non-resonantly pumped red-emitting vertical external cavity surface-emitting laser system based on a multi-quantum-well structure with 20 compressively-strained GaInP quantum wells for an operation wavelength between 645-675 nm. Five quantum well packages with four quantum wells are placed in a separate confinement heterostructure in a resonant periodic gain design in quaternary AlGaInP barriers and cladding layers, respectively. The 3 λ cavity is fabricated on a 55 λ/4 pairs Al0.50Ga0.50As/AlAs distributed Bragg reflector. By bonding an intra-cavity diamond heatspreader to the chip, continuous-wave operation exceeding 700mW output power at a wavelength of 662 nm with a low threshold power of 0.8W was achieved. A thermal resistance value of R1 = 5K/W and R2 = 7K/W could be determined for our setup at operation heatsink temperatures of Ths = -28°C and Ths = 16°C, respectively. Measurements of the slope efficiency within a v-type cavity with different outcoupling mirror reflectivities lead to a cavity round-trip transmission factor of Tloss = 98.6% and an absorption efficiency of ηabs = 17.6%. Using a birefringent filter in a folded cavity, a maximum tuning range of 22 nm at a center wavelength of 667 nm could be shown. With this method wavelengths below 650 nm were observed. Utilizing a non-linear crystal for intra-cavity frequency doubling in this cavity geometry, coherent emission down to 322 nm could be detected. In the UV spectral range, a maximum tuning range of 10 nm could be measured at a center wavelength of 330 nm, so we could match the HeCd laser line at 325 nm.