The Berry Phase of a Slowly Varying Waveguide

Jeroen Tromp, F. A. Dahlen

Abstract

A wavetrain in a slowly varying waveguide has, apart from the familiar dynamical phase or eikonal, an additional variation in phase which fixes the location of crests and troughs. This additional slow variation in phase is a multidimensional analogue of the Berry phase of an adiabatic quantum system. Both the quantum geometric phase and the additional variation in phase in a classical waveguide can be obtained from a variational principle based upon a slowly varying lagrangian.