Technical Issues - Importing Index Tables and Functions

RefractiveIndex.INFO

Dr. Mikhail Polyanskiy laudably maintains RefractiveIndex.INFO, a web compendium of n,k data for a number of materials. Data is presented in two formats: tables and dispersive formulas. Users should verify data and realize that film properties are different from bulk properties.

1. Tabulated tables have the following format (CSV). Note that lambda is in microns

lambda,n,k
6.199E-4,0.999512,7.50E-5
6.351E-4,0.999486,8.16E-5
6.508E-4,0.999459,8.87E-5
6.665E-4,0.999432,9.63E-5
...

CSV files can be automatically imported with FilmStar INDEX macro RefractiveIndexInfo.bas, included in the FilmStar installer or in basic32.zip. The program removes duplicate wavelength entries, so that the number of wavelengths may be slightly less than given by Polyanskiy. Data is also available in tab separated TXT files, handy for copying and pasting into Excel or into FilmStar INDEX. If pasting data, however, be sure to open INDEX's Index Table dialog to check for and remove duplicate wavelength entries. Some of the index tables have very wide wavelength range. We have consequently modified INDEX's auto-scale function to use log wavelength axis when the max/min wavelength ratio is >=20.

2. A variety of Sellmeier-type relations are utilized for glasses and similar materials. These can be imported into DESIGN and INDEX by clicking 'Expressions for n' and copying the Visual Basic code to the clipboard and pasting into the User Index Function Formula dialog as shown below. Be sure to leave out 'n ='.

Dy2O3 website original: SQR( 1 + x^2/(0.3653*x^2-73e-4) )

Dy2O3 DESIGN/INDEX: SQR( 1 + x^2/(0.3653*x^2-.0073) )

Since DESIGN 2.61.0103 and INDEX 2.51.0102, most formulas can be used directly because x now substitutes for WM (wavelength in microns). A few formulas utilize scientific number notation which causes difficulties for FilmStar's equation parser. For this reason we replaced 73e-4 with .0073 (73*10^-4 works equally well.)


 

Luxpop.com

Another source for refractive index data is Guillaume Boisset's Luxpop.com. Click here for a direct link to the list of n,k files. While these have the same extension (NK) as Sopra files, formats are different. Users should verify data and realize that film properties are different from bulk properties.

Luxpop NK files can be imported with FilmStar INDEX macro LuxpopNK.bas, included in the FilmStar installer or in basic32.zip. Some of the tables have very wide wavelength range. INDEX's auto-scale function uses log wavelength axis when the max/min wavelength ratio is >=20.

INDEX 2.51.0120 adds Sub Display so that users may review the file header before proceeding. Users of older versions should comment out the following lines:

Display s$, "File Viewer - click <Close> to proceed", _ 
    9000, 4500, "Verdana", 10, 0
If MsgBox("Continue to import file?", vbQuestion + _ 
    vbYesNo, "Luxpop n,k") = vbNo Then End

Wavelengths are in Angstroms as indicated by the string '(A)'. If '(A)' is not found, a 'Wavelength multiplier' prompt is provided for nm and µm. (If you discover files in other units, please let us know.) NK files will open in Excel; use 'Text to Column' to convert column A into three columns A-C.

As displayed below, files may include hard X-ray to FIR wavelength ranges. The graph below includes 1175 data points.

In the graph below, wavelength range was reduced to VIS-NIR (52 points) by deleting lines in the Index Table. Hold down the <Ctrl+D> key to rapidly delete lines.