2.3 Dispersion Formula
The refractive indices for wavelengths other than those listed in this catalogue can be computed from a dispersion formula. As a practical dispersion formula, we have adopted the use of the Sellmeier formula shown below.
The constants A1, A2, A3, B1, B2, B3 were computed by the method of least squares on the basis of refractive indices at standard wavelengths, which were measured accurately from several melt samples.
By using this formula, refractive indices for any wavelength between 365 nm and 2325 nm can be calculated to have an accuracy of approximately ±5·10-6. These constants A1, A2, A3, B1, B2, B3 are listed on the left side of the individual catalogue pages. However, for some glass types, not all refractive indices in the standard spectral range are listed on the data sheet.
In such cases, the applicable scope of this dispersion formula is limited to the given refractive indices.
When calculating a respective refractive index, please bear in mind that each wavelength is expressed in µm units.