Submicron-diameter silica taper with a Bragg multilayer structure: observation for TE 01 and HE 11 mode guidance

Abstract

ABSTRACT We demonstrate confinement of light in a submicron-diameter silica core by adding a Bragg multilayer cladding. Simulation results show that silica core Bragg fibers with Si/SiO 2 multilayer claddings exhibit stronger mode confinement than air cladding silica fiber. The optical properties of Bragg fiber taper can be fine tuned via controlling taper diameter and multilayer structures. In experiment, TE 01 mode-shaped spots with full-width at half-maximum (FWHM) of 1.2 Pm are observed for the first time to our knowledge in solid-core Bragg fibers. By adjusting the refractive index of high index layer, HE 11 mode-shaped spots with FWHM of 0.75 Pm are generated by 1.1 Pm-core Bragg fiber tapers. The proposed devices will be good candidates as polarization selection and mode conversion devices for nano-optical applications. Keywords: Bragg fiber, tapered waveguide 1. INTRODUCTION In Bragg fibers 1 , light is confined in the low-index core surrounded by a multilayer Bragg reflector. Their modal properties have been well studied and it has been found that TE modes in a small-core Bragg fiber tend to be better guided than other modes