<> Material fitting

The blue line is FDT Fit line of . The green dot is the test data .
Material You can choose the material to fit in , This includes the materials you added .

fit Tolerance Fitting coefficient , Represents the error of the fit .

max coefficients In the multi coefficient material model , The maximum coefficient that can be used .( Generally, the value does not exceed 12)
imaginary weight Weight of imaginary part .

RMS error Actual fitting mean square error .

Adjustment method :
1. The real part doesn't fit well ( You can also watch it RMS error Actual fitting mean square error and fit Tolerance Fitting coefficient )
 RMS error<fit Tolerance, Increase appropriately max coefficients, reduce fit Tolerance.
If after fitting RMS error>fit Tolerance, Then the real part fitting is better .

The real part and the imaginary part imaginary weight handle
How about increasing it ( At least greater than 1)
Don't reduce it properly ( At least less than 1)
Fit and plot controls——specify fitrange When the light source is incident ( use bloch Boundary condition or scanning wavelength ) We set the wavelength here .

For other simulation cases , stay Simulation bandwidth settings Set the wavelength in , This setting matches that of the light source .
Material properties

standard view Standard type —— Wavelength range for light source
extended view range Extended —— Specifies all the recorded wavelength ranges of the material for the material library
specify view range Designated type —— For non-linear materials or to find the reason of material divergence
index—— Refractive index
permittivity—— Dielectric constant ( Use this term to fit more accurately )

<>FDTD region advanced setting

Simulation badwidth Set the wavelength range of time monitor and light source ( Not most of the time , Leave it alone ).
After point selection, the grid in this direction is forced to be symmetrical with the center of the simulation area .

stay pec Choose this material , Nothing else .

auto shutoff min And auto shutoff max The equivalent intensity of the light source in the simulation area is greater than / Less than the specified value , We'll launch the simulation .
auto shutoff max Parameter modification is often used in nonlinear simulation , Gain medium simulation .
Use in other situations auto shutoff min.

This option is for oblique incidence equal simulation , The software will automatically check the options , We don't have to operate .

You can separate files into blocks , In different countries cpu Run on , Improve operation speed and efficiency .

<> Simulation time and memory

3D and 2D
Memory requirement is the third power of the average grid density and the second power of the average grid density
Time demand average grid density fourth power average grid density third power
When the simulation confirms whether it is feasible , You can lower most of the precision parameters first , After getting the results quickly and looking at the trend, the simulation accuracy can be further improved .

<> Advanced lighting settings

<>Plane wave( plane wave )

source shape( Type of light source ): Optional Gaussian Gaussian beam ;Plane wave plane wave ; Large numerical aperture light source ;

amplitude Amplitude of light source : Strictly speaking , Plane waves don't have the concept of power , Because its area is infinite , So the power is infinite . But in order to inject light , We usually give one “ power ”( The amplitude is 1 In this case ), Then, the light source intensity is calculated according to the plane wave area in the anti seismic region .( the measure of area × strength = power )

phase(degrees) phase angle
injection axis( Direction of incidence ): along x,y,z axis .
direction direction : just , negative direction .
angle theta(degrees): Pitch angle x And z Angle between faces .
angle phi(degrees): azimuth y And z Angle between faces .
polariration angle(degrees): Polarization angle .
The direction of light propagation is determined by angle theta(degrees) and angle phi(degrees) decision , The polarization direction is determined by the polarization angle . The plane of polarization is perpendicular to the direction of light propagation .

Plane wave region , Generally larger than the simulation area .
there x,y,z The setting method is applicable to most light sources ( Except dipole light source ), Both represent the central position of the injection surface of the light source .span Represents the span .

set frequency/wavelength Set frequency / wavelength

set time domain Set time domain ( It is usually used when the pulse shape needs to be changed .)

bean options, Some options for drawing .

<>GaussianSource Gaussian beam

Some settings are common to plane waves , Because Gaussian light can be understood as plane wave under periodic condition . Additional consideration should be given only in aperiodic conditions .
use scalar approxination in
 waist radius w0:
 distance from waist:distance from waist>0, The light source injection surface is located on the right side of the beam waist , Grey line , The beam always diverges ;distance
from waist=0 It shows that the light source injection surface is located above the beam waist ;distance from waist<0, The light source injection surface is located on the left side of the beam waist , red thread , The beam first converges on the waist , And then diverge .

In the picture d namely distance from waist.

<>dipole source

In general ORED, Use in photonic crystal simulation .
use Electric dipole perhaps Magnetic dipole It depends on whether you want to see an electric field or a magnetic field .

The other options are almost the same .

<>TFSF Full field scattering light source

It is similar to plane wave , But for some scattering simulation .

<>Mode Source Mode light source

mode selection In TE,TM It's only meaningful in two-dimensional simulation . For waveguides , Use of optical fiber .