Lateral Lasing and ASE Reduction in VECSELs (Postprint)
Technical paper 1 Oct 2009-11 Jan 2011
AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH SENSORS DIR
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Vertical external cavity surface emitting lasers VECSELs are attractive for many applications due to their high-power, high-brightness outputs. In order to power scale the devices, the pump spot size should be increased. However, the large pump area greatly amplifies the guided spontaneous emission in the epitaxial plane. In order to efficiently power scale the devices, amplified spontaneous emission ASE and lateral lasing must be reduced. We begin by first reporting on the temperature dependence of the phenomena. Particularly, since the quantum well gain and bandgap are functions of temperature, ASE and lateral lasing are greatly dependent on the operating temperature as well as the pump power. The easiest method of quantifying the affect of ASE and lateral lasing is by removing the Fabry-Perot cavity formed by the chip edges. We have chosen two different methods Reducing the Fresnel reflections by patterning the edges of the sample, and depositing a layer of Ge on the edges of the VECSEL chip as the high index of refraction for Ge should reduce the Fresnel reflections and the absorption properties in the NIR regime should also act to prevent feedback into the pump area. Our research shows both of these methods have increased the performance and visibly decreased the amount of lateral lasing seen in the devices.
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