Improved Optical Coupling Based On A Concave Cavity Lens Fabricated By Optical Fiber Facet Etching

We report a low-fabrication-complexity and wideband fiber lens, which is formed by fiber facet etching and filling high refractive index UV adhesive. The optical field can be significantly shrunk by the facet lens so as to obtain improved optical coupling. Numerical simulations were carried out for different coupling conditions, on both fundamental mode and high-order mode, for a nine-mode fiber. The fundamental mode area can be reduced from 152.17 to 12.57 mu m(2), and the coupling loss between the fiber lens and a photonic waveguide can be reduced to -2.9 dB with over 1000 nm 3 dB bandwidth.