Reflection delay expression of light wave reflected by multilayer dielectric coatings

Recursion formula of the reflection coefficient of a multilayer dielectric coating has been deduced by employing the equivalent cavity model, based on the principle of multibeam interference. Using this formula, the paper shows that, around the central frequency of the coating, the complex reflection coefficient can be expressed as the product of the reflection coefficient for the central frequency and a phase factor. Further, the expressions for the phase and reflection delays have also been derived.