Two dimensional image scanning of movies using surface acousto-optic interaction

The scanning of two-dimensional black and white movies is described by using the interaction of light with surface acoustic waves. The modulation transfer function for the image scanner is derived. Further, it is shown that the spatial resolution is limited by the surface acoustic wave transducer bandwidth rather than the physical size of the exit pupil of the scanner.     

Prolonged acousto-optic interaction with Lamb waves in crystalline plates

The propagation and acousto-optic interaction of Lamb modes in an anisotropic plate of tellurium dioxide (TeO2) are studied numerically and analytically. In the case of a Y-cut X-propagating TeO2 plate, the very high elastic anisotropy of the crystal greatly modifies the dispersion curves, giving rise to their multiple oscillations. The existence ranges of backward Lamb modes increase with the mode order contrary to the case of isotropic plates. The quasi-collinear light scattering by Lamb waves is considered. Owing to the structure of Lamb wave field, a simultaneous light diffraction at two different optical frequencies can take place while Lamb waves are excited only at the single frequency. It is demonstrated with the Z-cut (110)-propagating plate that a small change in the acoustic frequency can result in a significant shift in the frequency of the scattered light.     

Detection of surface acoustic waves by scanning tunneling microscopy

A new method for the investigation of ultrasonic waves on surfaces of solids based on scanning tunneling microscopy is presented. A sinusoidal high frequency signal is added to the tip voltage. Hence the tunneling current contains a component whose frequency is the difference of the frequencies of the acoustic wave field and the ac tip voltage. Amplitude and phase of this component carry the full information about the wave field.     

Wide-aperture acousto-optic interaction in birefringent crystals

Regularities of the wide-aperture mode of light diffraction by acoustic waves in crystals with different values of birefringence are considered. The diffraction has been investigated theoretically and experimentally with the aim of applying it in acousto-optic filters used in processing uncollimated optical beams and images. It is proved that the main filtration parameters depend on the birefringence of crystals used in processing luminous fluxes. By the example of wide-aperture filters based on paratellurite, magnesium fluoride, and potassium dihydrogen phosphate crystals, it is shown that the choice of crystals with high birefringence may increase the maximum attainable angular aperture and throughput of devices. It is also proved that application of crystalline compounds of mercury and tellurium (characterized by high optical anisotropy) in filters increases spectral resolution and improves the quality of filtered images.     

Polarization effects at collinear acousto-optic interaction

Collinear acousto-optic diffraction of an arbitrarily polarized optical radiation is studied theoretically and experimentally. It is shown that in the general case the diffracted light spectrum at the acousto-optic cell output consists of four components with different frequencies and polarizations. Beatings of these components lead to intensity modulation of the light passed through an output analyzer. Dependences of output intensity components on ultrasound frequency and acoustic power are examined for different orientations of the polarizer and the analyzer. Experimental investigations are carried out with a collinear acousto-optic cell fabricated with calcium molybdate single crystal.     

Optimal conditions of the acousto-optic interaction in crystals with gyrotropy

The conditions of the acousto-optic interaction in the crystals with gyrotropy are considered. The optimal length of the acousto-optic interaction and the diffraction efficiency in the gyrotropic direction are calculated. The diffraction efficiency is determined by the coupled wave method which allows calculation of the field interaction in the gyrotropic crystal [1]. It is theoretically shown and experimentally confirmed that the diffraction efficiency in the gyrotropic direction is independent of incident light polarization, when the polarization plane rotates by 45° along the interaction length.     

Bragg interaction of surface magnetostatic waves with a periodic granular HTSC structure

The Bragg interaction of surface magnetostatic waves with periodic granular HTSC structure has been investigated. The dispersion equation for the coupled waves has been obtained. Resonant absorption of waves near the critical temperature involving the granular structure of the superconductor has been found. The possibility of using the observed effect for making frequency-selective structures and high-speed bolometric photodetectors is shown. Tomsk University. Radio Electronic and Control Systems. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 94–98, October, 1997.     

Acousto-optic interaction with leaky surface acoustic waves in Y-cut LiTaO3 crystals

The acousto-optic interaction with leaky surface acoustic wave radiation into the bulk of YX-cut LiTaO₃ crystals has been investigated. The light incidence and diffraction angles corresponding to the strongest acousto-optic interaction were calculated and measured as functions of the acoustic wave frequency. The dependencies of the diffracted light intensity on the amplitude of radio-frequency voltage applied to the interdigital transducer (IDT) were studied. Our acousto-optic measurements revealed generation, by the IDTs, of slow shear bulk acoustic waves propagating at different angles depending on their frequency. A secondary acousto-optic interaction from the bulk waves radiated by the receiving IDT has been studied.     

A computer model of the interaction of acoustic surface waves with discontinuities

Surface acoustic waves are under active investigation in three fields of study: geophysics, electronics and non-destructive testing. While the mathematical features are the same for all three fields, the wavelengths, as well as the dimensions of the features, range over at least ten orders of magnitude.In this paper a brief review of available numerical techniques is presented and this is followed by discussion of a series of models which use finite difference methods to predict the reflected and transmitted signals from wide band pulses of ultrasonic Rayleigh waves incident on various surface-breaking features. The paper concludes with a comparison of analytical, numerical and experimental results.     

Effect of parametric refraction upon acousto-optic interaction

The interaction of optical and acoustic beams is studied for the case of a violated Bragg matching condition. The optical beam experiences self-action due to a cascade nonlinearity. Acousto-optic interaction can result in total reflection of the optical rays from the ultrasound beam.     

Sound generation due to the interaction of surface waves

Two opposite gravity-capillary waves of equal frequency give rise to the formation of a standing wave on the ocean surface and, thus, in the nonlinear approximation, generate a sound wave of twofold frequency with an amplitude proportional to the squared height of the surface wave [1]. This effect, being caused by the nonlinear interaction of opposite surface waves, can give rise to the radiation of sound waves in both ocean and atmosphere [2]. Opposite waves can appear in the ocean as a result of different ocean-atmosphere interactions and, in particular, as a result of the blocking of capillary waves on the slope of a gravity wave.     

Application of ultrasonic surface waves in the detection of microcracks using the scanning heating laser source technique

This letter reports the application of the scanning heating laser source technique to detect microcracks that may be undetected by conventional methods.In the proposed approach,we monitor changes in the transmitted surface acoustic waves(SAWs) as a heating source is scanned over the crack.The experimental system for microcrack detection by a scanning heating laser source is obtained by exploiting the strong dependence of the transmission efficiency of acoustic pulses on the state of the contacts,whether open or closed,between the crack faces.Microcracks can be detected successfully by confirming the heating position at the point of maximal improvement of the transmission efficiency of the SAWs.     

Stern-Gerlach spin filter using surface acoustic waves

We propose the ambipolar carrier transport by surface acoustic waves (SAWs) in a semiconductor quantum well (QW) for the realization of the Stern-Gerlach (SG) experiment in the solid phase. The well-defined and very low carrier velocity in the moving SAW field leads to a large deflection angle and thus to efficient spin separation, even for the weak field gradients and short (μm-long) interaction lengths that can be produced by micromagnets. The feasibility of a SG spin filter is discussed for different QW materials.     

Nanoscale self-organization using standing surface acoustic waves

The diffusion of an adatom on a substrate submitted to a standing surface acoustic wave is theoretically studied. By performing large scale molecular dynamic simulations, we show that the wave dynamically structures the substrate by encouraging the presence of the adatom in the vicinity of the maximum displacements of the substrate. Using an analytical model, we explain this feature introducing an effective potential induced by the wave. Applied in an atomic deposition experiment, this dynamic structuring process should govern the nucleation sites distribution opening the route to accurately control the self-organization process at the nanoscale.