Subwavelength Silica-Based Optical Waveguide With a Multilayered Buffer for Sharp Bending

A subwavelength SiO₂-based optical waveguide with an air cladding and a multilayered buffer is presented. This multilayered buffer includes alternating low and high refractive index dielectric layers. The thicknesses of these dielectric layers are chosen optimally by using genetic algorithm so that the theoretical leakage loss of the present optical waveguide is minimized (<0.001 dB/mm at the central wavelength, e.g., 1550 nm). The modal analysis with a full-vectorial finite-difference method shows that the present SiO₂ optical waveguide has the ability of sharp bending with a very small bending radius (~ 10 mum).