Simplified study of guided modes in plasma cladded step-index optical fiber

In this paper, the effect of plasma cladding on the modal dispersion characteristics of guided modes is explored. The dispersion relation of guided modes which is derived employing the usual boundary conditions, show a strong dependency on the operating frequency. The numerical aperture of plasma cladded light guide decreases on increasing the operating frequency which is quite contrary to conventional dielectric optical fibers. Our study further revealed that this decrease in numerical aperture is more prompt at lower frequency and hence, an unusual dispersion characteristic is displayed by hybrid modes. The transverse modes display the usual dispersion characteristics with only exceptions that these modes occur in pairs with approximately equal cutoff frequency. We hope that the study will be quite useful to investigate the behavior of high power laser beam propagating through air core or hollow fibers.