Parabolic cylindrical waveguides: revisited

An analytical investigation is presented of a waveguide with parabolic cyli ndrical guiding section. It is assumed that the waveguide has a step-index profile. and the refractive index of the guiding region is slightly higher than that of the two non-guiding regions so that the scalar field approxima tion in optical waveguides can be employed for the analysis. The eigenvalue equation for the cutoff modes is derived, and it is solved without using a ny field approximations. The plots represent a bunching tendency of modes i nstead of well-defined discreteness. which is because the distance of separ ation between the two laver interfaces does not remain constant, but contin ues to increase instead as one moves away from the region near the vertices of the parabolas. It is also found that by making the analysis more exact. the guide supports less number of modes, which is of advantage in the poin t of view of applications of such guides in optical communications or other related fields.