High coupling tapered hyperbolic fiber microlens

We propose a new scheme of a tapered hyperbolic-end fiber (THEF) microlens for efficient coupling between laser diode and single-mode fiber. The THEFs were fabricated by symmetrically tapering the fiber during the etching process and hyperbolically lensing the tip during the fusing process. The influence of tapering asymmetry on the coupling has also been investigated experimentally and theoretically. The axially symmetrical tapered microlenses of the THEFs showed far-field profiles well approximated by a Gaussian profile, while the asymmetric taper deviated significantly from a Gaussian profile. The high-coupling performance of hyperbolic microlens was due to the improved mode matching between laser and fiber. The hyperbolic microlenses of the THEFs have demonstrated up to 82% coupling efficiency for the laser with an aspect ratio of 1:1.5. To the best of authors' knowledge, this is the first report of hyperbolic mircrolens fabrication using unique etching and fusion techniques. Previously, the hyperbolic microlens was only available through laser micromachining techniques.