Fabrication and optical characteristics of large-core radial-firing optical fiber tip comprised of conically shaped air-pocket

Abstract

We report a large-core radial-firing optical fiber tip comprised of conically shaped air-pocket, fabricated by deforming a hollow optical fiber fusion-spliced with the large-core optical fiber (LCF) (core/cladding diameters = 200 / 220 μm) using the arc-discharge method. The effect of the intaglio air-pocket angle and the numerical aperture (NA) of the LCF on the radial-firing characteristics of the fiber tip was investigated. The design of air-pocket of the fiber tip was optimized for an effective radial-firing by simulating the beam profile of the radial-firing optical fiber with the ray-tracing method. The 45 deg of the conical angle with the low NA (0.12) of the LCF has shown the maximum radial-firing angle of 81 deg by the simulation. The fabricated LCF tip with the intaglio conical air-pocket with the 45 deg angle has shown the radial-firing angle up to ±78 deg, which was in good agreement with the simulation results. The present LCF radial-firing tip can be an effective element of medical devices for treatment of tubular shape tissues with the high-power transmission and the ease of operation in vivo.