Optically-pumped vertical-external-cavity surface-emitting semiconductor lasers

The optically-pumped vertical-external-cavity surface-emitting semiconductor laser (OP-VECSEL) is a versatile laser source that can generate high average power in a circular diffraction-limited beam. The diode-pumping techniques developed for solid state lasers provide uniform pumping over a large laser mode area, without the problems of filamentation experienced by injection-pumped VCSELS, while an external cavity enforces TEM₀₀ operation, and gives intracavity access to the laser mode. The OP-VECSEL thus combines many of the virtues of the diode-pumped solid state laser with the possibilities for engineering the wavelength, gain, dispersion and saturation characteristics offered by the semiconductor quantum-well gain medium. The gain medium incorporates a multilayer distributed Bragg reflector (DBR) adjacent to a number of quantum wells. Diode pump light is absorbed in the barrier regions either side of the quantum wells, generating carriers that are subsequently trapped in the wells. The interband barrier absorption is extremely broad compared to the pump bands of most dielectric laser media, conferring a relaxed pump diode wavelength specification. Our structures are grown by MOCVD on GaAs substrates, and designed to operate at ∼1030 nm, with a GaAs/AlAs DBR and 6 or 7 strain-compensated InGaAs/GaAsP wells. The wafers are used without post-growth processing.