U. Trutschel

TM-polarized nonlinear guided waves in multilayer systems

The ability of various multilayer systems to support TM-polarized nonlinear guided waves is studied. A flexible numerical technique which includes the proper consideration of the nonlinear crossing conditions is used to calculate the field profiles and derive the dispersion relations. The fundamentals of the model are described, and the algorithm is applied to several nonlinear film configurations. For the sake of comparison with the finite-element method, a single linear film, embedded between two nonlinear materials, is treated. A three-film unit cell, consisting of a high-index linear film, sandwiched between two low-index nonlinear, ones is considered. This is the elementary unit cell of a composite geometry, a ten-unit-cell superlattice, which is then studied. It is found that unlike TE-polarized nonlinear guided waves in multilayer systems, the TM waves reveal a distinct power maximum. The inclusion of saturation effects in the analysis is straightforward. >

Dispersion relations for nonlinear guided waves

Abstract The dispersion relations for TE-polarized nonlinear slab-guided waves are investigated numerically. The relation between the effective dielectric constants, the dependence of the propagation constants on an effective slab thickness together with some characteristic field patterns are indicated in diagrams. The whole arrangement is expected to be higly multistable.

Nonlinear transmission resonances at stratified dielectric media

Abstract For an oblique s-polarized incident wave, we study the optical response behaviour of dielectric multifilm systems containing an arbitrary number of film components with dielectric coefficients that have a self-focusing Kerr nonlinearity. The optical field propagation is rigorously described in the framework of Maxwells theory, permitting the determination of such properties as transmittance/reflectivity and the dispersion relations for guided wave solutions by means of a straightforward matrix calculus reminiscent of linear thin film optics. We discuss the angular transmittance characteristics of various geometries and monitor the evolution of selected transmission resonances with the incident power flux as the tuning parameter. Under conditions where transmission resonances compete with distinct reflection mechanisms, such as total internal reflection or Bragg reflection, the angular transmittance peaks show steep slopes, which tend strongly towards backbending, thus connecting the excitation of these transmission resonances with all-optical switching effects. Transmission resonances without linear limit, mediated by the excitation of specific nonlinear guided wave fields, have been identified too.

Cross trapping of two counterpropagating nonlinear guided waves

A model describing the mutual sustaining of two counterpropagating nonlinear guided waves is presented. Dispersion relations and field profiles are calculated for spatially stationary waves, revealing an invariable transverse field pattern down the waveguide. Particular emphasis is laid on the discussion of cross-trapping effects that diminish the necessary power for nonlinear waveguiding. Proposals concerning the potential exploitation of the resulting effects are given.

Optical bistability in three-wave-mixing processes with guided waves

In this paper the response curves of an integrated Optical three-wave-mixing configuration are investigated. In contrast to degenerate four-wave-mixing (DFWM) configurations the shape of the response curves can be dynamically tuned by one of the input intensities and frequency switching is possible. For contradirectional input wave launching, optical bistability can occur. The versatility of the operational principle should permit the implementation of an opto-optical modulator, switch, limiter, or a logical device respectively within a fixed configuration.

Analysis of the dispersion relation of nonlinear slab-guided waves

The dispersion relations of TE-polarized nonlinear guided waves (NGWs) in a symmetrical slab configuration (linear slab embedded between two identical media with a Kerr nonlinearity) are investigated in detail. Among even and odd NGWs the waveguide can support also NGWs, revealing an asymmetrical field pattern. The excitation of these NGWs requires a minimum guided power flux indicating a bifurcation of the corresponding dispersion curves.

Phase-controlled switching in nonlinear multiport fiber couplers

The background of the phase-controlled switching behavior of nonlinear multiport couplers is investigated. For the two-core device a direct correlation between the concept of nonlinear eigenmodes and the spatial dynamics can be found. In aligned and triangular three-core geometries the interpretation of the dispersion relations of the nonlinear eigenmodes, as well as the introduction of power portraits, turns out to be useful in identification of those initial states that prepare the system for sensitive switching operations. Some opportunities for optimizing the input–output characteristics are discussed.

Nonlinear ellipsometry: a first approach

We present, for what is to our knowledge the first time, the theoretical calculations of the ellipsometric parameters of a single nonlinear layer–substrate system (Fabry–Perot cavity) and of a nonlinear attenuated total internal reflection configuration. Using an analytical solution of the nonlinear wave equation in a medium with a weak third-order nonlinearity of thermal origin, we can determine theoretically the ellipsometric parameters for an incident linearly polarized monochromatic plane wave. We show that the sensitivity of the ellipsometric parameters with respect to the input flux and to changes of the nonlinear coefficient depends strongly on the sharpness of the linear resonances of the system. We propose ellipsometric experiments that permit the determination of small nonlinear coefficients.

Polarization-induced optical switching in a single nonlinear Fabry–Perot resonator

The transmission characteristic of a single nonlinear Fabry–Perot resonator, illuminated by arbitrary polarized and obliquely incident stationary plane waves, is presented. Using an analytical solution of the nonlinear wave equation, we show that the response characteristic depends strongly on the state of polarization of the input field. This effect is exploited for polarization-induced switching.

An effective medium model for TM-polarized nonlinear guided waves in multilayer systems

An effective medium model for TM-polarized nonlinear guided waves is derived. It is shown that a periodic multifilm configuration can be described as a single film with effective dielectric tensor components. Unlike in the TE-case these tensor components depend on the local fields and hence cannot be defined globally. Numerical investigations indicate that the effective medium model can be applied for most situations. >