Abstract

A new scheme for lensed fibers with a high focusing power is proposed. The new lensed fiber has a high-index layer coated (HILC) on a convex-shaped endface of a single-mode fiber (SMF). Numerical investigation shows that, by coating a 10-$\mu$m-thick film with refractive index of 3.7, the lensed fiber can contract the beam diameter of the propagating mode from 10.4$\mu$m at the wavelength of 1.55 $\mu$m, to 1.2 $\mu$m. The enhanced focusing effect of the lensed fiber has been confirmed experimentally by coating an $a$-Si:H film on the lensed endface. The measured focused spot diameter was as small as 1.6 $\mu$m, much the same as the wavelength.

© 2009 IEEE

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