Study and simulation of the effects of geometry and materials on the detection potential of tapered fiber sensors

In this paper, we have proposed three types of taper structures called L.C.C (L : linear, C : concave and C : convex) that form at the end of the optical fibers in order to use them for detection in order to improve the formation of evanescence waves on the surface of the fiber We studied on these three types of structure four materials such as: silicon (Si), glass (SiO2), sapphire (Al2O3) and zircon (ZrSiO4) with refractive indices 1.45, 1.52, 1.77 and 1.92, respectively. First, three tapered shaped structures were designed with a length 'L' set at 50 & mu;m and a diameter 'D' equal to 10 & mu;m. Then, they shrink to 1 & mu;m in diameter 'from the end of their structures. We used an optical DC source with a power amplitude of 1 Vm(-1). We also simulated these 'L.C.C' structures with the OptiFDTD simulation software, which is based on the finite difference time domain (FDTD) method. The numerical results obtained are: the transverse electric (TE) distribution of the evanescent wave (EW) and the leakage wave (LW) from the left end of the tip for the proposed taper structures. Finally, we presented the transmission. The results obtained showed that the geometric shape (such as the shape of the taper structure) and the type of material (such as the refractive index 'n') are very important. These play a crucial role in creating the evanescent waves in the tapered region of the sensor for sensing, which can be used to demonstrate the application of the desired sensor.