Cladding Medium Research Articles

Calculation of nonlinear waves guided by optical fibers with saturable nonlinear core and cladding: a resonance-technique approach

A recently developed, simple and easily programmable method based on the resonance technique for the analysis of nonlinear guided modes for fiber geometry is extended to include more complicated configurations. As an example of the proposed methodology, the following configuration is treated: a circular optical fiber consisting of a nonlinear core bounded by a nonlinear cladding medium. The calculation of the nonlinear modes in this case has some peculiarities and is presented in detail. The nonlinearity considered is of the more general type, including the saturable mode, which is of current significant importance. The numerical results obtained by this method correspond to the weak-guidance approximation and include both field distributions and power calculations. Some useful conclusions are deduced.

Fibre mode expansion for 2-D waveguide calculations

A numerical method is introduced which is devised to calculate the lower-order modes of optical waveguides with two-dimensional transverse index profiles embedded in a homogeneous cladding medium. We propose a method based on a series expansion using guided modes of an optical fibre. To test the method, it is applied to a three-layer optical-fibre and the results are compared with the exact analytical solutions. The error in the calculation of the modal effective indices is found to be less than 10−6. This method allows the modelling of symmetric 2 × 2 completely fused fibre couplers. Effective indices and polarization corrections are compared with results obtained by the field correction method. The adiabaticity criterion is calculated for these couplers.

Calculation of Nonlinear Waves Guided by Optical Fibres Using the Resonance Technique

Abstract A recently developed, simple, and easily programmable method based on a resonance technique for the analysis of nonlinear guided modes for planar geometry has been extended to include fibre configurations. We consider here nonlinear media of the general type (non-Kerr media) including the more complicated but realistic case of saturable media. In the present paper, as an example of the proposed methodology, the following configuration is treated: a circular optical fibre consisting of a linear core bounded by a nonlinear cladding medium. The numerical results obtained by the method, correspond to the ‘weak guidance’ approximation, including both field distribution and power calculations.

Evolution of nonlinear guided waves along a bent planar waveguide

AbstractOptical field propagation in a nonlinear bent slab waveguide with a Kerr‐like nonlinear cladding medium is presented. With increasing input power, the self‐focusing effect significantly disturbs the original waveguide configuration, and a nonstationary evolution behavior is found. It is shown that the onset and the direction of soliton emission are sensitive to the guiding capability of the initial waveguide. In particular, a novel result is observed when the waveguide supports more than one mode. © 1993 John Wiley & sons, Inc.

Propagation phenomena of nonlinear guided waves in graded-index planar waveguides

The dispersion relations, stability to propagation, absorption effects and Gaussian beam excitation of nonlinear TE waves guided by graded-index planar waveguides with both Kerrlaw and saturable nonlinear cladding media are discussed numerically. The spatial soliton emission and the effects of linear absorption on spatial soliton emission in graded-index planar waveguides with Kerr-like nonlinear cover media are investigated by numerical techniques. The stationary field distribution and the guided wave power flow-effective mode index relationship are obtained using the finite element method. The propagation down the waveguide of nonlinear TE waves excited by a specific input beam is investigated numerically using the Crank-Nicolson finite-difference scheme combined with the Newton-Picard method for solving the corresponding system of nonlinear equations.

Emission of spatial solitons from nonlinear waveguides

One of the unique features of nonlinear planar waveguides is that spatial solitons can be emitted into a self-focussing cladding medium. In this paper we discuss this phenomenon for a variety of models for the nonlinear medium, and show that soliton emission persists even when nonideal media are employed. We discuss the conditions for the emission and trapping of such solitons.

Uniform theory of inhomogeneous waveguide modes near cut-off

A uniform asymptotic method is used to calculate the modal eigenvalues for an inhomogeneous dielectric waveguide for modes near cut-off, thus extending previous work (ibid., vol.13, p.347 (1980)) on uniform methods. The existence of a finite homogeneous cladding medium is properly accounted for, with arbitrary variations of core refractive index.

Propagation of inhomogeneous waves in cladded optical fibres†

This paper describes the propagation of waves in cladded optical fibres consisting of a graded core medium in addition to a uniform cladding medium. The influence of cladding on propagation characteristics is discussed by means of modal ray optics. The present theory is developed for a general class of cladded inhomogeneous optical fibres.

Theory of Bragg fiber*

The possibility of using Bragg reflection in a cylindrical fiber to obtain lossless confined propagation in a core with a lower refractive index than that of the cladding medium is proposed and analyzed.

Light-wave coupling to optical waveguides by a tapered cladding medium

A transition from a symmetric to an asymmetric waveguide can serve as a mode- and polarization-dependent light-wave coupler. Coupling experiments with an efficiency up to 70% are reported. Furthermore, total reflection occurs at the transition if the angle of incidence of the guided wave exceeds a critical value. Coupling and total reflection are explained, using the concept of the effective refractive index.