Low-loss laser-to-fiber coupling with negligible optical feedback

A novel lens design for the coupling of single-frequency lasers to monomode fibers achieves both high coupling efficiency (> 40 percent, best value 70 percent) and extremely low optical power feedback (
\sim 10^{-7}
of the emitted power). The lens is formed out of a ∼ 1 mm length of a silica thread fused to the monomode fiber, with the open end of the silica thread modeled as an aspherical lens.