Development of a Multiple Beam Combiner Using Stimulated Raman Scattering in Multimode Fiber

摘要

Beam combination was demonstrated by splitting the beam from a Q- switched Nd:YAG (Neodymium:yttrium- aluminum-garnet) laser and pumping a multiple input, single output fiber squid. Beam cleanup of the resulting output beam using stimulated Raman scattering was then demonstrated in both 100 micrometer fiber and 200 micrometer fiber. Energy conversion efficiency into the Stokes beam was measured as a function of input energy and found to be limited by the attenuation characteristics of the fiber. Beam quality was measured via the M(2) fit parameter as a function of input energy and was found to slightly degrade in both fibers as input energy increased. In addition, beam quality was measured as a function of 100 micrometer fiber length and determined to degrade slightly at fiber lengths less than 400 m. Additional fiber length beyond 400 m did not improve beam quality and reduced output energy, although the Stokes threshold was reduced. The performance of the 200 micrometer fiber was compared to that of the 100 micrometer fiber.