Lakshminarayanan, VasudevanCalvo Padilla, María Luisa2023-06-202023-06-201987-060740-323210.1364/JOSAA.4.001037https://hdl.handle.net/20.500.14352/59093© 1987 Optical Society of America. This work was supported in part by grant EY03674 from the National Eye Institute, National Institutes of Health, Bethesda, Md. M. L. Calvo was supported by a grant from the U.S.- Spain Joint Committee for Scientific and Technological Cooperation Program. We thank J. M. Enoch for support and encouragement.An exact formulation of the electromagnetic field striking an optical waveguide is presented and compared with the decomposition relationship used in the literature. The expression for the critical angle is derived as a natural consequence of this formulation. Equations for the total fraction of power confined within a waveguide are derived and analyzed for the special case of absorbing waveguides. An explicit expression is derived for the fraction of energy confined within a waveguide supporting two sets of modes.engjournal articlehttp://dx.doi.org/10.1364/JOSAA.4.001037http://www.opticsinfobase.orgopen access535OpticsÓptica (Física)2209.19 Óptica Física