A. K. Ghatak

Analysis of rectangular-core dielectric waveguides: an accurate perturbation approach

We report the exact solution of the scalar-wave equation for a rectangular-core waveguide structure and develop a perturbation analysis for evaluating accurately the propagation characteristics of practical integrated-optical structures. We show that the present method gives results that are more accurate than other analytical methods reported earlier.

A novel design of a dispersion compensating fiber

We propose a novel dispersion compensating fiber design consisting of two highly asymmetric concentric cores. We show that the fundamental mode of the proposed fiber can have very large negative dispersion values [/spl sim/-5100 ps/(nm.km)] with larger mode field diameter (/spl sim/8-9 /spl mu/m) relative to the existing dispersion compensating fibers.

Bent planar waveguides and whispering gallery modes: a new method of analysis

A matrix method for analyzing bent planar optical waveguides is discussed. The method is a modification of an earlier method which yields bend loss directly, inasmuch as a nonuniform refractive index is approximated by a series of linear profiles rather than a series of uniform profiles. The method can be used with absorbing or leaky structures. The effect of whispering gallery modes has also been studied. It appears that a whispering gallery explanation given by H.J. Harris and P.F. Castle (1986) may not be adequate. >

Simple numerical technique for the analysis of cylindrically symmetric refractive-index profile optical fibers

We extend an earlier proposed matrix method for the analysis of cylindrically symmetric arbitrary refractive-index profile optical fibers to calculate the propagation constant and leakage/absorption loss of modes. This method involves only straightforward multiplications of 2 x 2 matrices and is highly attractive, since no complex plane iterations are performed even to obtain leakage or absorption losses. Thus the method is ideally suited for implementation on desktop computers. The applicability of the method has been shown through calculations of propagation constants and leakage loss of the LP(01) mode in depressed inner clad fibers.

A variational analysis of single mode graded-index fibers

A variational method is presented to obtain the transverse electric field and the propagation constant of the fundamental mode of weakly guiding graded-index fibers. A comparison has also been made with results obtained by using other approximate methods and it has been shown that the present method gives extremely accurate results (in comparison to other methods) in the practical region of single mode operation and does not involve much computational effort.

Prediction of coupling length in a rectangular-core directional coupler: an accurate analysis

It is shown that, for rectangular-core directional couplers, Marcatilis widely used analysis [Bell Syst. Tech. J. 48, 2071 (1969)] predicts almost the same value of coupling length as that obtained by the simple slab-waveguide approximation. A more accurate analysis, which takes the effect of corner regions into account through first-order perturbation theory, shows that Marcatilis analysis may lead to inaccurate results for small values of depths of channel waveguides, which are the most practical directional couplers involving single-mode channel waveguides.

Numerical analysis of optical fibers using matrix approach

The authors conduct a numerical analysis of optical fibers characterized by arbitrarily graded, cylindrically symmetric refractive index profiles by transforming them into equivalent planar profiles and using a matrix approach developed earlier for the analysis of planar optical waveguides (see ibid., vol.5, p.660-7, 1987). The method, which involves only straightforward multiplication of 2*2 matrices, can be used to calculate the propagation constant, modal field profiles, leakage/absorption loss, etc. of fibres with arbitrarily graded profiles. The applicability of the method has been shown through calculations of propagation constant and modal fields of single-clad and coaxial step-index fibers. Calculations of leakage loss of LP/sub 01/ and LP/sub 11/ modes in depressed inner clad fibers have also been presented. The method was also used to determine the coupling length in a coaxial optical-fiber coupler, which has potential applications in optical-fiber sensing. >

Waveguide polarizer based on resonant tunneling

A novel and highly efficient waveguide polarizer which is based on the phenomenon of resonant tunneling is proposed. Designs for both transverse-electric (TE) and transverse-magnetic (TM) pass polarizers based on this principle are suggested, and it is shown that with such a device it is possible to achieve TM mode loss greater than 80 dB/mm and TE mode loss less than 0.5 dB/mm for the TE pass polarizer, and TE mode loss of 24 dB/mm with a TM mode loss less than 0.8 dB/mm for the TM pass polarizer. >

A matrix approach to study the propagation characteristics of a general nonlinear planar waveguide

A simple matrix approach, which involves multiplication of 2*2 transfer matrices, is developed to study the propagation characteristics of a nonlinear planar waveguide. Numerical results for some nonlinear structures are presented and compared with the exact and previously published numerical results. It is shown that results obtained by the present approach are very accurate. In addition, the present method can be applied to arbitrary refractive index profiles with arbitrary nonlinear dependence. >

Beam propagation under frustrated total reflection

Abstract We report a study of the beam propagation problem with reference to the phenomenon of frustrated total reflection, and obtain analytical expressions for the reflected and transmitted fields and their lateral shifts as a function of the frustrating layer thickness. We consider an incident gaussian beam and discuss its propagation through a lossless dielectric layered structure.