Wsf : Electromagnetic field simulator by FDTD

Calculation principle

Wsf uses the calculation principle of FDTD (Finite Difference Time Domain), which sequentially solves the difference equations of Maxwell's equations in the time domain based on the arrangement of electromagnetic field vectors in the Yee grid.
 Maxwell's equations


 Yee grid and electromagnetic field vector


 difference formulas


 Calculation flow

Types of boundary conditions

 In the case of a periodic boundary condition (PBC).


 In the case of a perfectly matched layer (PML).

Types of oscillating direction

 In the case of unidirectional oscillation.


 In the case of bidirectional oscillation.


 In the case of laterally unidirectional oscillation.

Types of oscillating waveforms

 Example of pulse oscillation.


 Example of CW oscillation.

Calculation for a far field

 Inclined CW light is oscillated from the middle surface to the bottom surface.


 The far field pattern in the downward direction is calculated for the model shown above.

Dispersive material calculations

In many dispersive materials such as Al, the decay coefficient is larger than the refractive index, and the FDTD algorithm runs out of control.
 Wsf has applied the PLRC methodology, including in the PLM domain, to achieve stable calculations even for dispersible materials.

Measurement of light amount

 The amount of light inflowing and outflowing to materials and the amount of light absorbed by each material can be measured individually.


 Measurement result for each material region.

Calculation for a scattering field

 The scattered field can be calculated separately from the total electromagnetic field.


 The 360-degree far field pattern is calculated for the model shown above.

Calculation of a frequency spectrum

 Example of frequency response calculation for BPF using pulse oscillation.


 The wavelength dependence of reflectance and transmittance appear in the frequency spectrum.

Examples of cross-section for various structures

 In the case of internal definition.


 In the case of external definition using sub.dat.
The isolated structure can be defined by the four points (x1,y1), (x2,y2), (x3,y3), and (x4,y4) described in sub.dat.


The structure defined by the piled data of four points. A periodic pattern for these structures can be defined easily.

Calculation for lens focusing

 The lens shape is expressed by stacking the internally defined circular structure.


 The lens shape is expressed by stacking the externally defined circular structure.

Displaying the calculation results

At runtime, the calculation results are displayed in real time by Wsmnt and Wscnt.
 Displayed by Wsmnt.


 Displayed by Wscnt.