Please refer my attached paper for mathematical relation between dielectric constant and the refractive index.

Please refer my attached paper for mathematical relation between dielectric constant and the refractive index.

thank you but i know that the real part of dielectric constant  is equal at n², for ZnO that have a small thickness. for multiple layers thin film how we calculate the constant dielectric and how we can calculate the refractive index.

For dielectric constant measurements, you have to sandwich your film between two evaporated electrodes, i.e., M I M structure. Use any standard Capacitance bridge to measure dielectric parameters.

thank you Mr Gupta and Mr Kumar for your collaboration,