Current profiling and transverse mode control in broad area lasers

High power, high brightness semiconductor lasers are required for applications such as pump sources for fiber amplifiers. The increase of the stripe width of lasers constitutes a method to overcome the limitation of narrow stripe lasers. However broad area semiconductor lasers have poor coherence properties due to the appearance of filamentation and higher order transverse modes. Here, we analyse the coherence properties of high power semiconductor lasers with a modified transverse current profile. Our experimental investigations are based on conventional stripe geometry high power edge emitting devices incorporating an extra p type spreading layer to smooth the carriers from the usual top hat injection profile. We also use a lithographic half tone technique to achieve the desired injection profile. Current profiling could also be implemented in vertical cavity lasers with proton implementation or inhomogeneous optical pumping