The four vector equations, appropriate to a mixed type I-type II second-harmonic generation in a thin planar waveguide made from a second-order nonlinear material are solved both approximately and exactly. The solutions offer a richer set of possibilities than just Type II and always involve for both the harmonic and the fundamental. A new kind of polarisation control is shown to be possible, through which CW shut down, of one component of the second harmonic is achieved. The extinction angle is shown to depend strongly upon the phase mismatch parameter. In a second application, for solitary waves, an aperture is placed at the output and it is shown that if approximate stationary states are used as an input then varying the angle of incidence of two input beams produces an excellent output control. It is shown that a switch from 80% of the input energy arriving at the output port to less than 3% is possible.

Nonlinear waves in the form of solitons in magnetic films are attracting attention because of the interesting possibility of making novel spatial, and temporal, soliton devices that will operate in the technologically important microwave (GHz) frequency window. Some fascinating pioneering experimental work has been performed in this area and there is now every possibility that manipulation of solitonlike microwave pulses will be the basis of an entirely new range of devices. Both theory and experiment show that solitons are extremely robust and behave rather like particles. Magnetic films look set to become as successful as optical fibers in supporting bright envelope solitons; yet soliton behavior can often seem hard to comprehend. While they are subtle in their behavior they can be understood from many points of view that are physically, or mathematically, based. This presentation will explain what bright microwave envelope solitons are, drawing upon as much physical insight and analogy as possible. The necessary and sufficient conditions for soliton existence will be carefully set out, especially with respect to their relationship to the input conditions of a device. A substantial number of numerical examples will be used and the prospects for major expansion in the experimental area will be assessed. In the latter part of the presentation some important applications for solitons will be addressed. These will include the analysis of a switching device but logic devices, and various forms of pump–probe arrangements, will also be retrieved. Finally, the optimistic view that solitons in magnetic materials are now realistic tools will be expressed and the opportunities provided by dark and higher-dimensional solitons will be discussed.

Self-channeling and nonlinear beam shaping of magnetostatic waves in thin in-plane magnetized yttrium-iron-garnet films have been observed. Different power levels of a cw signal were launched into a magnetic film using a short microstrip antenna. A Brillouin light scattering system was used to observe the profile of the beams. Self-channeling of the magnetostatic wave beam occurred because of the interplay between the diffraction of the beam and nonlinearity, which leads to self-focusing. This was observed as the input power reached a threshold value equal to a few hundred milliwatts. A discussion of the observations is presented, together with estimates of the parameter ranges.

To date, relatively few papers have been published on the subject of WDM (Wavelength Division Multiplexing) as applied to a soliton communication system[1-8]. However, with the advent of TDM, (Time Division Multiplexing) and considering the effects of Gordon-Haus jitter, the bit repetition rate limit can be reached even for short pulse widths and it is now natural to look for methods of increasing the information throughput with different frequency bit-streams.

Thermal magnetic excitations in epitaxial Co films deposited on GaAs(001) surfaces have been studied at room temperature using Brillouin light scattering. The films have thicknesses in the range 3 to 20 nm. The variations of MSSW frequency with applied field at constant wavevector and the variation of MSSW frequency with wavevector at constant field have enabled the magnetizations and anisotropy fields to be determined. The variation of MSSW frequency as the films were rotated about the incident light axis enabled the form of the anisotropy to be determined. >

It is well known that in linear theory, surface spin waves (SW) do not exist in a pure exchange-coupled ferromagnet for the case of free spins at the surface. However, in these approximations of the linear theory the plane volume spin waves (VW), propagating along the surface of a ferromagnet, satisfies not only the Landau–Lifshitz equation for the magnetization motion, but the boundary conditions for the free surface spins. Such VW can be unstable and can be transformed into SW under small changes of a magnetic medium, e.g., if the surface spins are partly pinned. In the present work a new type of self-localized SW in the ferromagnet has been considered. The existence of such waves is conditioned entirely by the nonlinear properties of a ferromagnet. The penetration length of such SW is proportional to 1/A, where A is a maximum of the magnetization amplitude on the surface of the crystal. The dispersion equations have been obtained for pure exchange and dipole-exchange nonlinear SW. In the latter case the influence of the second harmonic generation on the wave propagation at the fundamental frequency was studied. The conditions when the SW excites the VW, carrying the energy into the volume of the crystal, are derived. The nonlinear Schrödinger equation for the SW envelope amplitude was derived and its solitonic solutions are obtained. The estimations of threshold values for the wave numbers of the propagating waves are provided.

A type of self-localized, surface, dipole-exchange spin wave on a ferromagnet is predicted, the existence of which is controlled entirely by the nonlinear properties of the ferromagnetic medium. Dispersion equations have been obtained for dipole-exchange nonlinear spin waves and the influence of second-harmonic generation on the wave, propagating at the fundamental frequency, is investigated. The nonlinear Schr\"odinger equation, for the spin-wave envelope amplitude, is derived and its solitonic solutions are discussed. Estimates of the threshold values of the wave numbers of the propagating waves are obtained.

This paper develops and applies a new quadrature method for TM waves that is capable of dealing with any kind of nonlinearity. Explicit solutions of the nonlinear equations are not required and power-effective index curves can be developed in terms of relatively straightforward integrations (quadrature) over one of the field components. The integration limits may be a function of frequency and/or magnetic field. The basic theory necessary for a study of nonlinear magneto-optic or magnetoplasma devices is created. Strongly nonlinear effects will require matched indices and a magnetic field can provide an extra tuning element that can enhance this matching. The theory has the potential to lead to novel coupler configurations.

It is now becoming accepted that recent discoveries of new nonlinear magnetic excitations are stimulating a new growth area that will lead to a new range of microwave and millimetre wave devices1. The literature already contains elegant experimental work on magnetostatic surface wave (MSSW) solitons on YIG films2,3 and a study of chaotic spin waves. This presentation contains the first theoretical derivation of the existence criteria for MSSW solitons. Third-order nonlinearity is accounted for in the magnetisation equation and it is proved that envelope solitons occur for propagation oblique to the applied field. Finally, nonlinear diffraction of light from the MSSW will be considered by taking into account both Faraday and Cotton-Mouton effects in a new nonlinear permittivity tensor.

The propagation of nonlinear monochromatic surface magnetostatic waves in thin ferromagnetic films is investigated. It is shown that these waves are unstable above a certain threshold intensity causing satellite waves to be excited through magnon decay processes. It is shown that the small value of the threshold intensity is consistent with first-order (three-magnon) effects. In the regime where these effects are forbidden, another higher threshold intensity exists that is due to second-order (four-magnon) effects. Analytical forms for the threshold intensities, together with numerical estimates, are also presented.

TE guiding structures consisting of an optically linear dielectric film embedded in dissimilar optically nonlinear unbounded media, are investigated for hysteresis properties. It is shown that many important features can be determined without a knowledge of the electric fields in the nonlinear media and that the eigenvalue equation yields a relation between the guided-wave vector and the field amplitude at the boundary. The power in the system is the important physical quantity and is carried by asymmetric modes that, in the linear limit, are neither odd nor even. This paper explores some of the limitations of such asymmetrically loaded linear dielectric films and shows that they can exhibit optical hysteresis.