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A rigorous modal cutoff analysis of plastic‐clad parabolic cylindrical waveguides: Maxwell's field approach

Using Maxwell's field equation, an analytical treatment is presented of a step‐index parabolic cylindrical waveguide. The waveguide materials are chosen such that there remains an appreciable difference between the refractive‐index values of the guiding and nonguiding regions, and a strong guidance of electromagnetic waves can perform. Moreover, the chosen materials are in use in the fabrication of low‐cost optical waveguides. The cutoff eigenvalue equation for the waveguide modes is derived under this rigorous condition. Further, no approximations for fields are used in the analysis. A comparison of the results is made with that published earlier on this problem. The analysis shows that the guide supports a fewer number of modes, which is an indication of the possible applications of these guides in optical communications and other related areas. Due to the waveguide geometry, the guide loses its well‐defined discreteness, and a kind of mode bunching is attained; the bunching tendency of modes is found to be much more prominent in this rigorous approach. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 151–156, 2001.