Dear Andrea Cordone ,

you should google by yourself:

So you will find for example:

The wavelength depencene of the refractive index described by the Sellmeyer equation:

https://www.rp-photonics.com/sellmeier_formula.html

https://en.wikipedia.org/wiki/Sellmeier_equation

You will find there the following link on dispersion coefficients for a lot of glasses:

https://refractiveindex.info/.

For SiO2 and GeO2 see for example Table 1.2 of:

https://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwichZe76LbsAhVCDewKHX4LCkIQFjAQegQICxAC&url=http%3A%2F%2Fcatalogimages.wiley.com%2Fimages%2Fdb%2Fpdf%2F9780470021927.excerpt.pdf&usg=AOvVaw2kah81O8qyyRKlxWEZ5QLy

I also found your homework exercise...

https://www.chegg.com/homework-help/using-sellmeier-equation-coefficients-table-92-calculate-ref-chapter-9-problem-4qp-solution-9780073104645-exc

Good luck

non absorbing films follow the cauchy dispersion model while semiconducting films typically follow the tauc-lorentz dispersion model.

Dear Andrea,

perhaps help the following data.

Yours

R. Mitdank