Passively mode-locked red VECSEL

During the recent years, the wavelength coverage of optically-pumped vertical external-cavity surface-emitting lasers (VECSELs) has expanded significantly and currently reaches from the UV to mid-IR (although not without gaps). This progress has been fuelled by the ability to tailor the VECSELs emission wavelength via bandgap engineering and by the capability to deploy different kinds of semiconductor gain material systems, such as GaAs, InP, GaSb and PbTe, for example. The combination of wavelength flexibility and efficient intra-cavity second-harmonic generation makes these lasers excellent light sources for many applications for which conventional solid-state laser aren't available. In particular, the development of frequency-doubled VECSELs with blue, green and yellow-orange emission has experienced a surge of outstanding achievements.