IDEAL MICROLENSES FOR LASER TO FIBER COUPLING

We report the design and fabrication of ideal microlenses for semiconductor laser to fiber coupling. Properly coated for reflections, lenses of the new design can theoretically collect 100% of the radiated energy of a modal-symmetric laser source. The crucial feature is its hyperbolic shape. Microlenses fabricated directly on the end of the fiber by laser micromachining have demonstrated up to 90% coupling efficiency. This performance represents a major advance in microlens technology when compared to currently fabricated hemispherical microlenses which are at best 55% efficient. A theoretical comparison or the two lens shapes illuminates the advantages of the hyperbolic profile. The ability to couple all of the light from a semiconductor laser into a fiber has far-reaching implications for all optical communication systems.