Wave Optics Module Updates

For users of the Wave Optics Module, COMSOL Multiphysics® version 5.6 brings a new study step for faster port sweeps, a Polarization plot type, and several new tutorial models. Read more about the news below.

Polarization Plot Type

The Polarization plot type depicts the polarization state for the different diffraction orders seen in a periodic structure, such as a frequency-selective surface or metamaterial. It is used for default plots when periodic ports are included in the simulation, and can be added manually when postprocessing. You can see this new plot type used in the Hexagonal Grating (Wave Optics) model.

Polarization states plotted for three diffraction orders where the phases are shown in rainbow radians.
Polarization states for three diffraction orders in the Hexagonal Grating model.

Time-to-Frequency FFT Study for the Electromagnetic Waves, Transient Interface

Use the Time to Frequency FFT study type to first make a broadband transient study. The time-domain data is then transformed to the frequency domain, using a fast Fourier transform (FFT). This study type is now available for the Electromagnetic Waves, Transient interface in the Wave Optics Module. You can see this new feature in the Time to Frequency FFT Analysis of a Distributed Bragg Reflector model.

A 1D plot of transmittance comparing results for a time-to-frequency FFT study and a regular frequency sweep, where the two lines are nearly identical.
The transmittance of a distributed Bragg reflector (DBR) using a time-to-frequency FFT study (blue) and a regular frequency sweep (green).

Oblique Angle of Incidence for Scattering Boundary Condition in Mode Analysis

For mode analysis, the Scattering boundary condition can now use an oblique angle of incidence. That is, it can efficiently absorb waves with a wave vector composed of the mode's propagation constant directed tangentially to the boundary and a remaining normal component. This improves loss calculation in mode analyses for lossy waveguides. You can see this new feature in the Leaky Modes in a Microstructured Optical Fiber model.

Four 2D models of a microstructured optical fiber, visualizing different patterns in a rainbow color table for tangential electric field, tangential magnetic field, longitudinal electric field, and longitudinal magnetic field.
This graph shows the norm of the tangential and longitudinal electric and magnetic fields for one of the two degenerate HE11-like modes in a microstructured optical fiber.

Input Power to Control Gaussian Beam Amplitude

For Gaussian beam background fields and input fields to the Scattering and Matched boundary conditions, the amplitude of the beam can be specified by providing the input power. You can view this in the Self-Focusing model.

The electric field of a Gaussian beam modeled in a rainbow color table
The normalized electric field for a Gaussian beam propagation through a medium with an intensity-dependent refractive index. The higher intensity, the larger the refractive index becomes, and the tighter the beam is focused.

Reference Point Defined by a General Expression

The Reference Point subfeature to the Scattering and Matched boundary conditions can now be specified from a general vector expression. This makes it simpler to parameterize the propagation direction of input Gaussian beams for these boundary conditions.

A Gaussian beam propagating in an arbitrary direction toward the focal plane at the center of the circle.

Synchronization of Material Parameters Between Related Material Property Groups

The relative permittivity, refractive index, loss tangent, and dielectric loss material properties can synchronize the material parameters between groups. Thus, if a material is added and specified by the refractive index material property group, the Electric Displacement Field setting in the Wave Equation, Electric node can be any of the mentioned material models. If the required parameters are not directly available in the material, the parameters are created using a synchronization rule.

New Curl Shape Function

The Nédélec finite element of the second kind is now available. This element type, or shape function, has full polynomial orders in all directions for each field component. This can give a solution to certain finite element problems for lower shape orders, or with coarser meshes, and it can also make the resulting fields look smoother in postprocessing. You can see this new functionality in the Orbital Angular Momentum Beam model.

A rainbow phase plot of an orbital angular momentum beam.
An orbital angular momentum beam. The use of the new curl shape function makes the phase plot look smoother.

Solving for Fast Port Sweep

Use the new study step, Frequency Domain Source Sweep, to run a frequency domain study that is sweeping among ports and lumped ports calculating a full S-parameter matrix. The settings for this study step are similar to those for the Frequency Domain study step, and much simpler than the traditional port sweep, which requires a parametric sweep step. You can see this new feature in the H-Bend Waveguide 3D model.

Enhanced Usability of Eigenfrequency Study

The eigenfrequency study has been updated to reduce the number of modeling steps and enhance usability. After the eigenfrequency simulation, the eigenfrequencies and Q-factors are automatically evaluated and presented in a table.

New Tutorial Models

COMSOL Multiphysics® version 5.6 brings several new tutorial models to the Wave Optics Module.