Remarks on Variational Bounds for Waveguide Scattering

Utilization of variational techniques has facilitated the solution of scattering problems. A variational principle which gives a bound on the scattering elements in waveguide problems is presented. The formalism is applicable to scalar and tensor type problems for single and multimode scattering. A variation-iteration method can be used to avoid the need for explicitly evaluating a Green´s function that appears in the formalism. Also, an alternative variational bound principle is outlined.