A robust full-vectorial mode solver for metalized fiber taper

摘要

Conically tapered fibers with dielectric or metalized waists or tips of a sub-wavelength diameter have the potential of a range of applications, from optical probes for near-field detection to (bio)chemical sensing in extremely small volumes of analytes.rnFor successful design, a robust modeling tool is a prerequisite. In such structures, strongly lossy modes with complex propagation constants with large imaginary parts may be excited. In this paper, a reliable eigenmode solver for cylindrical structures containing metal layers is described. An analytical function whose roots correspond to propagation constants of waveguide eigenmodes is formulated. Its roots are found with a help of Argument Principal Method. Due to the analyticity limitation, the waveguide structure has to be of a finite diameter with either electrically or magnetically conductive walls. The approach is implemented within the well-known modeling tool CAMFR. The feasibility of the method is demonstrated using the example of light propagation in the metalized fiber taper dipped in the surrounding medium.