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The optimum power coupling from GaAs lasers into spherical-ended fibers

The optimum coupling efficiency from a GaAs laser into a spherical-ended fiber is theoretically computed by the Gaussian beam approximation for describing the laser source and by the ray-tracing method for calculating the maximum acceptance angle of the fiber. An improvement factor of 1.6 in the coupling efficiency is experimentally measured and 1.8 is expected from the theory. Neglecting reflection losses, the result of calculations indicate that a coupling efficiency near 100 percent can be achieved by the proper use of spherical lenses with low-divergence laser sources.