Hollow-core photonic band gap fibers for particle acceleration

Abstract

Photonic band gap (PBG) dielectric fibers with hollow cores are being studied both theoretically and experimentally for use as laser driven accelerator structures. The hollow core functions as both a longitudinal waveguide for the transverse-magnetic (TM) accelerating fields and a channel for the charged particles. The dielectric surrounding the core is permeated by a periodic array of smaller holes to confine the mode, forming a photonic crystal fiber in which modes exist in frequency passbands, separated by band gaps. The hollow core acts as a defect which breaks the crystal symmetry, and so-called defect, or trapped modes having frequencies in the band gap will only propagate near the defect. We describe the design of 2D hollow-core PBG fibers to support TM defect modes with high longitudinal fields and high characteristic impedance. Using as-built dimensions of industrially made fibers, we perform a simulation analysis of prototype PBG fibers with dimensions appropriate for speed-of-light TM modes.

Dielectric laser accelerators

“…A rainbow color scheme (the legend) is used to represent linear magnitude of the relative field intensity with the red and blue colors being the maximum (1) and minimum (0), respectively. From Noble et al (2011). possibly even laser power amplifiers.…”

Dielectric Laser Accelerators: Designs, Experiments, and Applications

“…An alternative means of confining an accelerating field mode spatially is found through the use of photonic band gap (PBG) crystals, such as the hexagonal rod lattice shown in Fig. 2 [65]. A defect is introduced to the lattice in the form of a large hole in its center, in which a transverse magnetic (TM) accelerating mode along which electrons travel is excited [66][67][68].…”

Lorenz–Mie theory for 2D scattering and resonance calculations

“…where R nn is the center-to-center distance between scatterers n and n and φ nn is the angular position of scatterer n in the frame of reference of scatterer n. Substituting (42) in (38) yields…”

“…In this "extended" formulation, the complex eigenfrequency k QB of QB states described by equation (12) can be interpreted as a "transverse" propagation constant which can be used to compute a "longitudinal" propagation constant β using β 2 = k 2 0 − k 2 QB , where k 0 is the free-space wavevector. The modelling of MOFs constitute an important research topic, since these fibres can be used to accelerate charged particles using TMpolarized photonic bandgap defect modes analogous to those computed in section IV B. TM modes in hollowcore fibres are particularly appealing for electron acceleration since they exhibit only a longitudinal electric field parallel to the fibre axis [38].…”