High Power Fiber Laser with Extremely Large Mode Area

The proposed project, in partnership with Nufern, will demonstrate the feasibility to scale high power fiber laser at the eyesafe wavelength of 2 microns up to 75-kW power level and beyond. This will be accomplished using an array of extremely large area core by means of a Self-Fourier cavity monolithically attached to the individual fiber laser. In this configuration, the Self-Fourier cavity performs spatial filtering on the operating laser mode of each individual fiber laser as well as that of the array and filters out the unwanted higher order modes of operation; allowing operation of the laser in a single diffraction limited beam and yielding high beam quality output. Demonstration of this technology will further enhance the power capabilities of high-power laser systems if used in conjunction with coherent beam combination currently being demonstrated using a Self-Fourier cavity The Phase I project will experimentally demonstrate the spatial filtering properties of the Self-Fourier cavity used with Tm doped active fibers fabricated by Nufern. The SF cavity will be monolithically attached to the fiber lasers using a proprietary technology recently developed by Corcoran Engineering for the Army SMDC. The results of the Phase I effort will be a demonstration of the performance capabilities of this spatial filtering mechanism, a good understanding of the scaling issues for high power operation, and a design for Phase II prototype. The Phase II effort will demonstrate a diffraction-limited laser source at a power level of more than 200W. Development of this technology will pave the way for high energy laser systems useful for many other military applications including high energy laser weapons as well as the pumps for these systems.