High Brightness Beam-Coupler for High Power Diode Lasers

"High brightness lasers have been identified as a means of producing acceptably short and reliable munition ignition times in large caliber guns. For practical purposes, these lasers must be compact, low-cost, efficient and robust to withstand the harshshock environment. High power multiple emitter diode bars can meet these criteria, but poor beam quality (typical M2>1000 from a single 50W bar) and low spatial coherence are incompatible with the high brightness requirement for ignition. CTI proposes anovel, compact and efficient active beam-combining architecture, capable of dramatically enhancing the combined brightness of multiple diode bars to generate near diffraction-limited output. The beam-coupler has excellent heat dissipation, and aproprietary architecture that virtually eliminates thermo-optic beam distortions. In one possible configuration, up to twelve 50W diode bars are butt-coupled into, and combined in, a single 70mm long lightweight module. Modeling, anchored by our recentproof-of-concept demonstrations indicates a brightness enhancement of more than 300x with respect to the direct diode output. Modules may be stacked to scale power to multi-kW levels, as required, without loss of brightness. CTI's proven ability todesign and engineer rugged and compact electro-optic systems for demanding environments will ensure a successful overall development program. Anticipated applications include (1) ignition systems for