Abstract

A waveguide problem with a balance between loss and gain has been defined by one of the authors (H.-P. N.) in the COST 240, Working Group 2, to study the mode behaviour in the case of complex refractive index and to compare different approaches. This problem is many-layered in both senses of the word. We will not discuss the numerical aspects of finding all roots¹ of the dispersion equation, we will give a quasi-analytic solution for the branching point of the dispersion diagram, define a new BPM benchmark test, and discuss the peculiar wave behaviour of this waveguide.

© 1996 Optical Society of America