BLACK Diodes

From 1985 to 1998, nearly $175M was invested in developing coherent semiconductor laser arrays in the Air Force PILOT program. However, the laser systems that were ultimately deployed from this program were either single-element lasers or incoherent laser arrays no viable coherent arrays were produced. The key remaining challenges to producing coherent semiconductor laser arrays are: (A) Both individual emitters and coherently combined arrays fall pray to spatial and dynamic instabilities due to inherent nonlinearities in the semiconductor medium. (B) The large number of laser elements required to reach Directed Energy Weapon (DEW) power levels dictate that active phase control of the diodes is required, impairing the overall system with a large and cumbersome overhead. We propose a qualitatively new approach to semiconductor laser beam combination that overcomes these obstacles. Specifically, we propose to develop a coherent semiconductor laser system that provides: (1) Mitigation of spatial and dynamic nonlinear instabilities (2) Strict diffraction-limited single-lobe emission (3) Inherent scalability with no complex controls, active feedback, or phase stabilization The new methodology is scalable both in parallel and concatenated serial application, and enables for the first time the use of broad-area semiconductor lasers with diffraction-limited beam quality.