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High Average Power Diode Laser Illuminator. Phase 1/Phase 2.

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The Phase I effort was directed toward verification of cryogenic laser diode optic technology for optical throughputs of more than one watt average power per fiber. In the test model, 17 diode modulefiber units out of a complement of 28 were operated simultaneously the bundled fibers formed a 60 by 80 mil source which emitted 21 watts at 9 per cent duty factor through an f 1.6 optical system. The test model circular array configuration imposes disadvantages during fabrication which prevents successful operation of the full complement of modulefiber units. The Phase II task consisted of design studies and experiments to evolve a linear laser diode fiber optic array. An electrical analog model of the array thermal resistance path was constructed to experimentally solve the three-dimensional heat flow problem. A Gallium-Indium eutectic solder which is a liquid at room temperature was developed to provide a high conductivity interface material. Conceptual array designs were examined for modularity, ease of fabrication, and repairability. Sub-array tests using extruded optical quality fibers indicated potential fiber melting due to the insulating vacuum surrounding the array. A theoretical analysis of fiber cooling using a nitrogen gas filled array chamber showed a marked advantage for gas-cooled fibers. The proposed final design is a linear, modular array using equal length metallized fibers in a gas-filled chamber. The source size is 66 x 66 mils using 30 diodefiber units on 15 modules. Author

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Final rept. 2 Apr-16 Nov 73,



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