Dear Asim,

one solution to this problem is to use the data of the refractive index n and calculate from it the relative dielectric constant epsilonr,

It is so that epsilonr= n^2, For such material we have further mur=1 as the material in nonmagnetic.

We have further mu= mu0 . mur and epsilon= epsilonr epsilon0.

Then you can calculate the terms in your equation if you know the refractive index n.

For the refractive index n you can get it from the link:https://en.wikipedia.org/wiki/Barium_borate

One has to pay attention that this relation is valid in the optical frequencies where n is measured.

Best wishes

thenks ' Abdelhalim Zekry ' for the response.

i am trying to electro optically tune the BBO crystal , in which my refractive index is a variable quantity, and as per the relation quoted " epsilonr= n^2 " , the epsilonr will be a variable quantity . so is it so that the permeability will change when the refractive index for the material changes.