Direct blue laser emission from InGaN-based VECSEL

Abstract

Vertical-external-cavity surface-emitting lasers (VECSELs) combine desirable features from several types of solid-state laser devices. Both high optical output power and a nearly diffraction limited beam quality can be simultaneously achieved. High-performance VECSELs with InGaAs or InGaAsP active zones are commercially available. However, until recently VECSEL emission in the near-UV and blue spectral regime has been only accessible through frequency multiplication. In this presentation, we demonstrate direct blue laser emission (? = 440 455nm) from an InGaN-based VECSEL. The laser heterostructures were grown on bulk GaN substrates by using MOVPE near atmospheric pressure. The active zone consisted of 20 InGaN quantum wells distributed in a resonant periodic gain configuration. High-reflectivity dielectric distributed Bragg-reflectors were used as mirrors. The concept of in-well pumping opens the possibility to use compact high-power GaN-based laser diodes as pump sources in future applications. The in-well absorption allows pumping through the GaN substrate and, therefore, the possibility to mount a heat sink close to the active zone. Furthermore, the approach reduces the thermal energy dissipation due to the low quantum deficit between the pump and lasing emission energies. Finally, homogeneous carrier generation throughout the distributed MQW region can be achieved, which is essential for high-performance VECSEL operation. An all-optical measurement technique was developed to determine the thermal resistance of the prototype VECSEL devices. The non-optimized thermal management could be identified as the limiting factor toward CW operation. *The work was supported by the U.S. Defense Threat Reduction Agency (DTRA) under U.S. Army Cooperative Agreement No. W911NF-10-2-0008.