Electromagnetic fields and transmission properties in tapered hollow metallic waveguides

Abstract

Abstract:We analyze the electromagnetic spatital distributions and address an important issue of the transmission properties of spherical transverseelectric (TE) and transverse-magnetic (TM) eigenmodes within a tapered hollow metallic waveguide in detail. Explicit analytical expressions for the spatital distributions of electromagnetic field components, attenuation constant, phase constant and wave impedance are derived. Accurate eigenvalues obtained numerically are used to study the dependences of the transmission properties on the taper angle, the mode as well as the length of the waveguide. It is shown that all modes run continuously from a propagating through a transition to an evanescent region and the value of the attenuation increases as the distance from the cone vertex and the cone angle decrease. A strict distinction between pure propagating and pure evanescent modes cannot be achieved. One mode after the other reaches cutoff in the tapered hollow metallic waveguide as the distance from the cone vertex desreases.

Numerical simulations of laser light guiding and focusing using an open hollow cone

“…Together with the cone angle, the tip size determines the laser intensification at the cone tip. This is because all propagating modes have a cutoff radius [19]. When the tip size is less than the cutoff radius, the corresponding mode cannot propagate, causing energy loss.…”

Characteristics and geometry optimization of a hollow cone for guiding and focusing laser light

“…It should be noted that the cone tip size can neither become too large nor too small. This is because all propagating modes have a cutoff radius [22]. When the tip size is less than the cutoff radius, the corresponding mode cannot propagate causing energy loss.…”

Fabrication of corrugated Ge-doped silica fibers

“…This transformation leads to miniaturization of information channels. Light concentrators have different forms from tapered fibers [1], either all-dielectric with a large core-cladding index contrast or metal coated ones [2], through tapered plasmonic waveguides with photon-plasmon couplers [3,4] ending at metamaterial nanotips [5]. Applications of light concentrators are numerous.…”