Advanced Cooling System for High Power Solid State Lasers

Through the Phase I SBIR process, Rini Technologies Inc. has demonstrated the feasibility of using evaporative spray cooling to reduce the temperature of high power laser diode stacks below the temperature at which they currently operate. This reductionin temperature, while operating at high power, results in increased laser efficiency, extended lifetime and reliability, as well as the ability to overdrive the output power above the rated power limit. The Phase II effort will focus on the development ofa prototype system that will cool a 1.4Kw diode laser source. The size of the stack will be 1cm x 7cm. During the development of the prototype, the following issues will be addressed; 1) scaling the spray technique from cooling 1cm2 to 7cm2, 2) designingand fabricating a compact nozzle array to spray the larger surface, 3) designing and fabricating a compact and efficient condenser unit to reduce the overall size of the system, and 4) selecting the optimum liquid pump to reduce cavitations, vibration andpower consumption. The prototype system will use a diode laser source provided by Decade Optical Systems, Inc. (DOS) DOS is a commercial and military solid state and diode laser manufacturer. They have partnered with RTI, and are providing matching funds($200k) for the Phase II development, and intend to purchase a spray-cooled system from RTI once the prototype development is complete. The first application of the spray cooled laser system is a 100kW solid-state laser (the Heat Capacity Laser) beingbuilt by the Army Space and Missile Defense Command (ASMDC). The Army intends to use RTI's evaporative spray cooling technology as the cooling source for the high power diode lasers that are the light source for the solid-state laser. ASMDC is likely toprovide matching funds to RTI as a level of $1.3M over the duration of the SBIR contract if this funding becomes available from the Joint Technology Office. The prototype cooling system will be developed at RTI's facility in Orlando, Fl, primarily by RTIpersonal. RTI will work with engineers from DOS to aid the design of the laser-to-cooler interface. The benefit of this prototype to high power diode lasers is a reduced operating temperature without increasing cooling costs. This is accomplished byimplementing a more efficient cooling mechanism. With reduced diode temperature, efficiency, lifetime and reliability are all increased. Potential markets include any high power diode application, such as, military weapons and countermeasures;industrial metal processing (welding, cutting, drilling); printing and surface marking.