In-Well Pumped Blue GaN-Based Vertical-External-Cavity Surface-Emitting Lasers

Abstract

We describe the properties of in-well pumped blue InGaN/GaN vertical-external-cavity surface-emitting lasers. The laser hetero-structures were deposited on bulk GaN substrates by using metal–organic vapor phase epitaxy near atmospheric pressure. The active zones are comprised of up to 20 InGaN quantum wells distributed in a resonant periodic gain configuration. High-reflectivity dielectric distributed Bragg-reflectors were used as mirrors. Lasing was achieved at a wavelength of about 440–445 nm by exclusively exciting the quantum wells with the 384 nm emission line of a dye/N2 laser. The laser threshold was about 240 kW/cm2. The small pump spot diameter of about 20 µm and the usage of dielectric mirrors result in a rather high thermal resistance, which was experimentally determined by using an all optical measurement technique based on the temperature-dependent change of the refractive index of the device.