FIMMWAVE

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‣ Stress Solver
‣ Electro-Optic Solver
‣ Thermo-Optic Solver
‣ Feature/Option Table

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Electro-Optic Module

for FIMMWAVE

This module is designed to model the electro-optic effects in a FIMMWAVE waveguide. Typically two or more metallic contacts are placed on or in the waveguide and a voltage applied to each. The module will determine the electric field distribution through the device and then generate a refractive index profile, taking into account the electro-optic effect. The algorithm takes full account of a varying material permitivity. Both the permitivity profile and the contact arrangements can be of virtually any geometry.

FIMMWAVE includes an anisotropic optical solver, which uses an optical refractive index tensor (currently with two non-zero coefficients ne_xx, ne_yy) – the Module is designed to determine the changes in these coefficients as a function of electro-static field vector E = (E_x, E_y, E_z), as well as calculating the field profile E(x,y). The altered refractive index profiles may then be used in optical propagation calculations.

Input Specification

The user may specify one or more contacts, each contact is assumed to be horizontal, but can be on top of or buried within the waveguide. The contact is an equipotential, with the voltage defined by the user. The Module uses the Material Database to determine the zero-field. The figure below illustrates some of the features of the model:

Output Results

• Potential distribution

• E_x, E_y and E_tot field distribution

• Modified waveguide (“RWG”) - refractive index altered according to electro-optic effect. This waveguide can then be used directly by the mode solvers, so that the user can investigate its optical properties.

• Estimated change in effective index of modes of the unperturbed (zero field) waveguide. If modes have been found for the unperturbed waveguide, then the Module will make an estimate of the change in effective index of the mode due to the electro-optic effect, using overlap integrals.

• Optical moment – this is an indication of how strongly the electro-static field is “pushing” the mode to the side and is very useful for optimising an electro-optic switch.

Calculation

The calculation is based on a 2D Poisson solver, to determine the electrostatic potential profile in the two transverse directions (X/Y). The algorithm takes into account a spatially varying permitivity and also electro-optic coefficient. The algorithm uses a rectangular grid but the grid spacing is varied so that for example thin layers are discretised precisely.

Materials are assigned a frequency dependent refractive index for DC to microwave range, independent of the optical index. The Poisson Equation Solver uses an anisotropic dc refractive index tensor with two non-zero coefficients: ne_dc,xx, ne_dc,yy.

Design Curve Generator

The Generator will calculate the variation of the estimated change in mode effective index as the dimensions and voltages on the contacts are varied.

Electro-Optic Module with FIMMPROP: Electro-Optic Switch Design

If you also have FIMMPROP, the Electro-Optic Module will allow you to model the propagation in a electro-optic switch – typically a Y junction with electrodes placed to induce the light to travel preferably on one branch or the other. The Module and FIMMPROP will work closely together to permit one to study the effects of the electro-optic effect on the optical propagation.