Study Evanescent-field Penetration Depth in Tapered Nano-fiber Optics

The use of etching in the fabrication of nanofiber optic (NFO) can enable the creation of thinner, longer, bundled, and strong wires. The aim of this etching methodology is to control the reduction of the core diameter and to demonstrate two different reducing methods applied to fabricate NFO. A large penetration depth of an evanescent field (EF) is the explanation of achievement for increasing a fiber-optic evanescent-field sensor (FOEFS). In general, the penetration depth (dp) of an optical fiber, stripped of its cladding, was a relation to the wavelength of the incident light, the refractive index (RI) of the surrounding medium and the incident angle on the basis of the ray-tracing model. Ray tracing analysis of tapered nano fiber optics segments and of combination taper probes make evident that the increases along the length of the taper, creating a segmented sensor with increased excitation light available at the surface for stimulating of ray transmitting. In this work, to study an NFO based on a tapered sensing probe by using the numerical analysis. The light power transmission and ultimate sensitivity of the element sensor are influenced by the incident angle, the numerical aperture (NA), core diameter, and taper ratio (TR). The TR of 0.1 and 0.7 are yield higher dp in certain regions. Then, the optimal result and the maximum dp were obtained with dp =1140 nm in TR=0.1 and a tapering length (L) of position tapering Z=40 mm.