Fabrication and characterization of probes for near-field spectroscopy

Abstract

In this project, the light propagating characteristics in tapered fibers are investigated via experiments and simulations. The tapered fiber is fabricated based on the heating and pulling method, where the propagation of light waves through the optical fiber is detected by the photo-detector and the light intensity is monitored throughout the pulling process. The simulation is based on the finite-difference time-domain (FDTD) technique, which is used to simulate the optical fiber at each stage of the pulling process. The structure of the tapered fiber used in the simulations is equivalent to the actual tapered fiber dimension. The throughput at different taper diameters, taper lengths and fiber lengths are investigated. The experimental study is compared with the simulation results to quantify the throughput characteristics of the tapered fiber. The throughput is found to decrease with decreasing taper diameter and the throughput is independent of the fiber length. A tapered fiber with a sufficiently small taper diameter will experience extreme sensitivity, where large fluctuations will result when the fiber is on the verge of breaking.