The objective of this project is to create a new class of high power, single frequency diode lasers in an integrated platform for emerging applications. We first focus on monolithic beam combining and use photonic crystal Bragg lasers as the building block to create monolithically coupled diode laser emitters and coherent arrays for high power, single frequency applications. This approach is innovative in that it simultaneously solves the most critical problems associated with beam control of high power diode laser arrays i.e., broad-area, single-transverse-mode emitters, single frequency operation, and monolithic beam combining. We then use hybrid photonic integration to realize coherent beam combing of diode lasers for high power, single frequency applications. In addition, we show that the proposed high power, single frequency sources are important for integrated nonlinear optics applications, such as microresonator based frequency comb generation.