A method of improving the coupling efficiency of an elliptical light beam into an optical fiber is achieved with a novel cylindrical concave microlens. Coupling efficiencies of 87% from single transverse mode diode lasers into single-mode optical fiber have been achieved with this microlens when used in conjunction with a pair of bulk optic asphere lenses. The microlens is amenable to production processes, is effective for a wide range of beam aspect ratios and represents a significant improvement over the 60 - 65% coupling efficiency which is typical of volume fiber coupling techniques to date.
Tanya K. Oleskevich,
"High-efficiency coupling for high-aspect-ratio laser diodes", Proc. SPIE 2610, Laser Diode Chip and Packaging Technology, (15 January 1996); doi: 10.1117/12.230088; https://doi.org/10.1117/12.230088