A conceptually simple, effective scheme for reliable, high-power pumping of neodymium:yttrium aluminum garnet (Nd:YAG) lasers (and perhaps also other solid-state lasers) has been devised. Heretofore, it has been common practice to pump a Nd:YAG crystal by use of a single diode laser. However, diode lasers are not reliable enough to support long-life, high-power operation. If multiple diode lasers could be used to pump a single Nd:YAG crystal, then laser operation would be less degraded by the deterioration or failure of a single diode laser.
One alternative scheme for coupling light from multiple laser-diode pumps into a single Nd:YAG crystal would involve the integration of multiple laser diodes, along with relatively complicated optics, onto a single chip. In such an arrangement, it would not be possible to change the number of pumps. Moreover, the pumps would not be isolated from each other, so that failure of one could adversely affect the operation of the others.
In contrast, the present scheme affords optical isolation of the pump lasers from each other, is amenable to addition or removal of pump lasers, and involves relatively simple optics. The output ends of the fibers of multiple independent fiber-coupled laser diodes are bundled together in a ferrule (see figure). A gradient-index-of-refraction (GRIN) lens in the ferrule combines the multiple pump beams into a single beam aimed into the Nd:YAG crystal. The failure of one laser diode does not affect the operation of the others, and the light from the others continues to pump the Nd:YAG crystal.
This work was done by Serge Dubovitsky, Jerry Mulder, and Duncan Liu of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Electronic Components and Systems category.
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