Optical fiber lasers are often used in commercial applications including remote sensing and materials processing. Because these applications can benefit from high-peak powers and pulse energies, there is a corresponding need to reduce nonlinearities caused by high-peak intensities.
Researchers have used a number of approaches to increase the effective area of the fibers in order to achieve large-mode area (LMA) high-power fiber lasers. However, with these techniques, the fibers are operated in the fundamental mode which creates a significant reduction in mode area when the fiber is coiled. The results are that it is difficult to scale the effective area of the fundamental mode beyond 1000 microns and peak powers are limited to a few hundred kilowatts. In this way, the robust and compact packaging benefits of high-power fiber lasers are often lost when LMA fiber designs are used.
In an article written for SPIE Newsroom, Dr. Jeff Nicholson of OFS Laboratories explains how his team overcame this problem using an OFS designed, bulk-optic mode converter that uses an axicon for the output of HOM (High Order Mode) fiber amplifiers.
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