Focusing properties of high brightness gain tailored broad-area semiconductor lasers

We present a simple broad-area semiconductor laser using a current spreading layer to modify the transverse gain profile. The device exhibits excellent spatial coherence to total output powers of 2.5 W under pulsed operation. Devices have been focused down to a spot size of approximately 5 μm full-width at half-maximum at 2.5 W, with the beam profile and position remaining stable over the entire range of operation. Under continuous-wave operation, thermal effects reduce spatial coherence, leading to a significantly increased spot size and loss of beam stability. This work demonstrates the advantages of modifying the transverse gain profile, and how it can be used to produce high brightness devices required for single-mode fiber coupling.