Effect of inner cladding thickness on the modal dispersion characteristics of annular-circular helical waveguides

Abstract

In the present communication, we have done an analytical study of inner cladded annular step-index waveguide with the different thickness of the inner cladding. With the help of the sheath-helix boundary condition on the inner core-cladding boundary and simple step-index boundary conditions on the outer core-cladding boundary, a general characteristics equation of the waveguide has been obtained. We have seen the effect of the inner cladding thickness on the modal dispersion characteristics of the helical waveguide. Presence of the negative dispersion curves and its dependence on the thickness of the inner cladding seems to be important findings. The dependence of the inner thickness on the modal dispersion property at the pitch angle of 0° has been studied. We have found out that the lowest cutoff value of the usual dispersion curve decreases on increasing the inner thickness of the helical waveguide and the forbidden region between the negative and positive dispersion curves called the Photonic Band Gap (PBG) also decreases. But the length of the negative dispersion curves increases slightly on increasing the inner cladding thickness. © Journal of Electromagnetic Waves and Applications. All rights reserved.