Nonlinear dispersive surface acoustic waves propagating on LiNbO3 single-crystal plates were studied. In order to control the dispersion, a thin SiO2 overlay was applied. Harmonic generation measurements in the crystals without SiO2 overlay show that the second-harmonic amplitude exceeds that of the fundamental wave when the initial wave amplitude exceeds 40 Å, and the spatial periodicity length of harmonic generation varies depending on power. In the samples with 500-Å-thick SiO2 coatings, no significant change of the periodicity length with power has been detected. In both cases we observed an increase of phase velocity with acoustic power. Comparison of the experimental data with the spectrum of Korteweg-de Vries solitons suggests the presence of surface acoustic wave solitons.

Absarrd--Mognetic perpendicular anisotropy constants of RF-sputtered amorphous TbFe thin films were measured by VSM and mngnetwptic techniques. Anisotropy depended heady 011 fUm thickness. We have found that the spontaneous magnetization changed with thickness in the same fashion as in the presence of a very thin (1 mu) highly magnetized interface layer. Msotropy measured from the top and bottom Alm surfaces revealed very different dependence on the deposition panmeten Because the magnetization reversal is incoherent due to the different anisotropy fields in the surface layers and in the bulk, it is necessary to account for the reversal mechanism to evaluate the true value of intrinsic anisotropy of the amorphous alloy.

A new type of laser probe for observation of surface-acoustic waves (SAWs) is presented. The probe operation is based on the knife-edge technique combined with an optical sampling method that employs a pulsed laser beam. The spatial resolution of the probe is 1.3 μm and its bandwidth is greater than 1 GHz. A highly nonlinear SAW involving 10 harmonics on single-crystal lithium-niobate (LiNbO3) plates has been studied at the input frequency 200 MHz. It is shown that the initially sinusoidal wave breaks into a train of pulses up to four per period with the evolution of time. The spectrum data were related to SAW harmonic generation studied previously under similar conditions. Head-to-head collision of two SAW wave packets of 500 ns duration has been studied. It was confirmed that the wave forms are preserved in the collision. In addition, the effect of nonlinear diffraction of a SAW driven by high input power levels was observed. The present probe is found to be a powerful tool for elucidation of SAW solitons.

The interference optics of analytical ultracentrifuges can be greatly improved by the installation of a laser. This will not only give a short exposure time and quite a few clearly discernible fringes in the interference pattern, but will also offer the possibility of achieving stroboscopic behaviour through the modulation of the emission by a multiplexer.In this paper we deal with the Beckman Model E, since it is the ultracentrifuge most widely used. Should it not already be equipped with a multiplexer, it can easily be retrofitted and utilised to modulate the laser. Special care, however, has then to be taken to suppress the contrastreducing background illumination that comes from two satellite orientations of the rotor at each passage of a cell. Suitable electro-optical devices are described.

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