We present an application of simple closed-form expressions based on a vari
ational approach for field parameters and effective indices for a closed-fo
rm analysis of diffused planar single-mode optical waveguides to obtain the
characteristics of diffused channel waveguides by a combination of the var
iational and effective-index methods. (C) 1999 Optical Society of America [
S0740-3232(99)00511-6].