This section describes how to import experimental material data into the Material database, and how to check the material fit with the Material Explorer. The Sampled 2D Data or Sampled 3D Data material type should be used when creating materials from measured data.
Alternative video source in Mandarin, click here
Adding a new material from a .txt data file
1. Create wavelength/frequency vs index/permittivity text file.
Save the experimental data in a 3 column text file, as shown below, and in the text file below.
420 5.08894 0.237724
440 4.78731 0.169323
460 4.57592 0.130235
480 4.4202 0.0933521
500 4.29748 0.0728287
520 4.19996 0.0568346
540 4.11973 0.0472312
560 4.05256 0.0362285
580 3.99543 0.027335
600 3.94724 0.0256523
620 3.90579 0.022
640 3.86838 0.0178648
660 3.83622 0.0159291
680 3.80661 0.013161
700 3.78304 0.0125603
The first column of the material files should contain the wavelength or frequency, and the second and third columns should contain the corresponding real and imaginary parts of the refractive index (n,k) or permittivity when specifying a Sampled 3D Data type material. When specifying a Sampled 2D Data type material, the second and third columns should contain the corresponding real and imaginary parts of the conductivity or resistivity. In this example, we will illustrate a Sampled 3D Data material with refractive index data over wavelength.
2. Open the Material Database and click the Add button.
Select the Sampled 3D Data option. This will create a new entry in the Material list. Set the material name and color by clicking on those fields.
3. Click on the Import Data button to import the material data from the text file.
Select the File to import, and the units of the data. Click Next.
4. Specify the column ordering
If the columns in the text file are not in the standard order of Wavelength - Real index - Imaginary index, use the following form to specify the order of the columns.
5.Automated error checking
If there are no errors, click Finish.
Adding a new material from a .yml data file
1. Identify material of interest from database.
Once you found the material of interest from the database, you can download the .yml file from Full database record option. From the list of available YAML files, tabulated n (example 2) and tabulated nk (example 3 and example 5) are the only types that can be imported. An example of tabulated nk is shown below:
# this file is part of refractiveindex.info database
# refractiveindex.info database is in the public domain
# copyright and related rights waived via CC0 1.0
REFERENCES: "G. M. Hale and M. R. Querry. Optical constants of water in the 200-nm to 200-µm
wavelength region, <a href=\"https://doi.org/10.1364/AO.12.000555\"><i>Appl. Opt.</i> <b>12</b>,
555-563 (1973)</a><br>See also <a href=\"https://refractiveindex.info/?shelf=main&book=H2O&page=Segelstein\"><i>
Segelstein 1981</i></a> for more recent data from the same group."
COMMENTS: "Liquid water (H<sub>2</sub>O) at 25 °C"
DATA:
- type: tabulated nk
data: |
0.200 1.396 1.10E-7
0.225 1.373 4.90E-8
0.250 1.362 3.35E-8
0.275 1.354 2.35E-8
0.300 1.349 1.60E-8
0.325 1.346 1.08E-8
0.350 1.343 6.50E-9
0.375 1.341 3.50E-9
0.400 1.339 1.86E-9
0.425 1.338 1.30E-9
0.450 1.337 1.02E-9
0.475 1.336 9.35E-10
0.500 1.335 1.00E-9
The first column of the material files is wavelength, and the second and third columns should contain the corresponding real and imaginary parts of the refractive index (n,k) when specifying a Sampled 3D Data type material.
2. Open the Material Database and click the Add button.
Select the Sampled 3D Data option. This will create a new entry in the Material list. Set the material name and color by clicking on those fields.
3. Import Data button to import the material data from the .yml file.
Select the File to import, and the units of the data will be automatically updated to index and wavelength (μm). Click Next.
4. If there are no errors, click Finish.
Adding a new material with a script
Use the addmaterial and setmaterial script commands to automatically create new materials. See the setmaterial script command documentation page for details, or this page for an example Importing arbitrary dispersive models.
Check the material fit
FDTD will fit the experimental data to a generalized multi-coefficient model supported in the FDTD simulation. The fitting routine only uses data within the frequency range of the source, it is best to setup the source frequency/wavelength settings before using the Material Explorer.
Once the source is setup, click the Material Explorer button to view the material fits. Select the material name and set the vertical axis to either index or permittivity. Click the Fit and Plot button.
The RMS error of this fit in the 400-700nm range of the source is quite small. This is not surprising, since these numbers are based on Silicon, which tends to fit very nicely. See the Modify material fits section for information about how to modify the material fits.
Anisotropic materials
It is also possible to create anisotropic sampled data materials if we set the 'anisotropy' property to 'diagonal'. The data import process is the same as above, except for the text file format. The file usr_sampled_data_anistropic.txt shows the required format for anisotropic data
400 5.57 0.387 2.785 0.1935 1.85667 0.129
420 5.08894 0.237724 2.54447 0.118862 1.69631 0.0792415
440 4.78731 0.169323 2.39366 0.0846613 1.59577 0.0564409
460 4.57592 0.130235 2.28796 0.0651175 1.52531 0.0434116
480 4.4202 0.0933521 2.2101 0.0466761 1.4734 0.0311174
500 4.29748 0.0728287 2.14874 0.0364144 1.43249 0.0242762
520 4.19996 0.0568346 2.09998 0.0284173 1.39999 0.0189449
540 4.11973 0.0472312 2.05986 0.0236156 1.37324 0.0157437
560 4.05256 0.0362285 2.02628 0.0181143 1.35085 0.0120762
580 3.99543 0.027335 1.99772 0.0136675 1.33181 0.00911168
600 3.94724 0.0256523 1.97362 0.0128262 1.31575 0.00855078
620 3.90579 0.022 1.9529 0.011 1.30193 0.00733333
640 3.86838 0.0178648 1.93419 0.0089324 1.28946 0.00595494
660 3.83622 0.0159291 1.91811 0.00796453 1.27874 0.00530969
680 3.80661 0.013161 1.9033 0.00658052 1.26887 0.00438701
700 3.78304 0.0125603 1.89152 0.00628013 1.26101 0.00418676
The first column is wavelength (or frequency). The second and third columns are the real and imaginary parts of the refractive index (or permittivity) in the X direction. Columns 4 and 5 are the real and imaginary parts of the index (or permittivity) in the Y direction, and columns 6 and 7 are the real and imaginary parts of the index (or permittivity) in the Z direction.
When using the Material Explorer to check the material fits, use the Axis drop down to view the material properties for each direction.
III-V Semiconductor Optical Materials
Optical material data for certain ternary and quaternary III-V semiconductor can be generated from theoretical models using the tool provided on the III-V Semiconductor Optical Material Data Tool page.
See also
Getting material data from the database, Creating lossless materials, Importing arbitrary dispersive models, Modify material fits, setmaterial, Creating 2D conductivity from permittivity data