FIMMWAVE

Modes of an ARROW Waveguide

Simulation of ARROW and hollow-core waveguide with FIMMWAVE software

Hollow waveguides allow to guide light in gaseous or liquid media, and offer a large range of potential applications in molecular sensing, thermometry and high-power laser delivery. The low refractive index of most gases and liquids rule out conventional index guiding for integrated optics. Optical guiding can nevertheless be obtained for periodic structures such as photonic crystals fibres or Bragg waveguides.

ARROW waveguides (short for Anti-Resonant Reflecting Optical Waveguides) offer an alternative to design hollow-core integrated waveguides in non-periodic structures.

Two designs of hollow-core ARROW waveguides were simulated with FIMMWAVE at 633nm, one based on an arch-shaped cross-section and the other one with a rectangular geometry. The results are reported in [1].

Modes of the arch-shaped ARROW waveguide
Modes of the rectangular ARROW waveguide

Images of hollow-core ARROWs with rectangular and arch-shaped cross sections
obtained by scanning-electron microscopy [1]

ARROW waveguides designed in FIMMWAVE

Modes of the arch-shaped ARROW waveguide

The FEM Solver, thanks to its highly optimised triangular mesh, is ideal for finding the modes of curved geometries such as the one of this arch-shaped cross-section.

Mesh of the FEM Solver for the arch-shaped waveguide;
the mesh only needs to describe half the cross-section thanks to the symmetry

The FEM Solver found the guided modes of the hollow waveguide within a minute. The simulation took advantage of the symmetry of the structure to gain in speed and accuracy. PMLs were used to calculate the optical leakage and associated mode losses.

FIMMWAVE allows you to check the accuracy of the modes by calculating the mode orthogonality, which in this case was found to be very good (mode overlap below 1e-5%). The mode profiles for the fundamental TE-like mode and first order TM-like mode are given below.

Arch-shaped ARROW waveguide: fundamental TE-like mode (Ex field)


Arch-shaped ARROW waveguide: first order TM-like mode (Ey field)

Modes of the rectangular ARROW waveguide

The FDM Solver was used to find the modes of the rectangular waveguide, with PMLs on each boundary condition to measure optical leakage.

The mode profiles of the fundamental TE-like mode and vertical first-order TM-like mode are given below. For the TM-like mode, you can observe the field profile corresponding to optical leakage in the cladding.

Rectangular ARROW waveguide: fundamental TE-like mode (Ex field contour plot)


Rectangular ARROW waveguide: vertical first order TM-like mode (Ey field)

Reference 

[1] Dongliang Yin, Holger Schmidt, John P. Barber, Evan J. Lunt, and Aaron R. Hawkins, "Optical characterization of arch-shaped ARROW waveguides with liquid cores," Opt. Express 13, 10564-10570 (2005) (PDF)

More publications 

Click here to find publications that include FIMMWAVE simulations of ARROW waveguides on Google Scholar.