High Efficiency kW-Class Semiconductor Laser Bars for Inertial Fusion Energy
Small Business Information
5408 NE 88th Street, Bldg E, Vancouver, WA, 98665-0990
AbstractTo realize laser-driven inertial fusion energy with economically viable efficiency and repetition rates, pumping the laser system with semiconductor diode lasers instead of the flashlamp will be essential. Diode laser prices are currently much too high for practical implementation of fusion energy. Novel technologies need to be pursued to scale up diode laser power while simultaneously reducing the costs, resulting in an order-of-magnitude improvement in costs/Watt. nLight proposes novel bipolar cascade diode laser architecture to address both the power and efficiency requirements, as well as the cost challenge placed upon diode laser technology. Power-scaling of semiconductor diode laser bars will be demonstrated by vertically stacked multiple laser diodes in one epitaxial growth, effectively reducing the cost of manufacturing laser diodes and high-power packaged assemblies. Under the Phase I program, nLight has successfully demonstrated the concept of epitaxially stacking two laser diodes on one substrate, resulting in two-fold increase in power without much sacrifice in efficiency. A maximum output power of 680 W with a peak overall efficiency of 63% was demonstrated for a 1-cm double-junction CS-mounted diode laser bar. Our diode laser models predict that not only can we further improve the efficiency but getting a three-fold increase in power is also feasible. During the proposed Phase II effort, nLight will optimize double-junction diode laser bars for higher efficiency, reproducibility and reliability. nLight will also explore further power scaling through design and development of triple-junction diode laser bars. Upon conclusion of the proposed program, a 10-bar stacked array with a rated power of 1.3 kW/bar will be fabricated and delivered. Commercial Applications and Other Benefits: Global energy demand is rapidly outpacing the world energy supply, and so the benefits that fusion energy could offer to society are obvious. The proposed development of high power, high efficiency and low cost diode lasers is essential in practical implementation of laser-driven inertial fusion energy. The proposed development would also have far-reaching impacts in current commercial applications that nLight is a leader in. For example, in the defense sector, high power, high efficiency QCW arrays are utilized in systems including rangefinders, target designators, 3D LIDAR imaging/surveillance cameras, illuminators and even as a fuse replacement for artillery ignition. In the industrial and aerospace sectors, QCW laser arrays are commonly used to pump solid state laser systems. One potential killer application which resides in the consumer sector is the direct use as a spark plug replacement in large engines which requires high peak power lasers
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