NASA's Langley Research Center has developed a compact, highly efficient, multi-purpose laser rod. This system employs a modular laser design with highly efficient and compact components. The laser consists of distinct building blocks to achieve wavelengths of 1.0, 1.5, and 2.0 microns. Amplifier modules are based on a novel hybrid fiber rod concept. By confining the otherwise highly divergent pump radiation to a small channel via total internal reflection at a moderately high numerical aperture interface, the low-brightness diodes can pump with high power density over a moderately long absorption path, thereby achieving highly efficient pump absorption.
For the new laser concept, a relatively short but large core fiber doped by active lasing material is used in place of a conventional solid-state crystal as the amplifier gain media in a free-space configuration. The technology avoids the usual problems of low thresholds for catastrophic optical damage and other nonlinear loss processes in fiber lasers by increasing the fiber core diameter of a standard 9-micron, single-mode fiber to the order of 1 mm, thereby permitting peak powers to be increased by factors of 10,000. The usual degradation of single-mode propagation in large-diameter fibers is avoided by keeping fiber lengths short, thereby staying within a free-space, single-mode propagation regime.