Surface Acoustic Wave Beam Research Articles

Single-electron acoustic charge transport by two counterpropagating surface acoustic wave beams

Single-electron acoustic charge transport by two counterpropagating surface acoustic wave beams

Characterization and imaging of SAW grooved transducer acoustic field by SLAM

Quantitative characterization of the surface acoustic field radiated forward, backward, and in orthogonal directions by the grooved transducer, implemented onto a glass substrate, is accomplished by a scanning laser acoustic microscope (SLAM) operating at 31 MHz. The surface acoustic wave (SAW) amplitude is measured as a function of the number of grooves and the position of the bulk acoustic wave (BAW) transducer. The number of the operating grooves efficiently contributing to the SAW response is estimated. Remarkable reflection of the SAW beam between two identical gratings is observed.

Propagation of laser-generated surface acoustic waves visualized by shake-off of fine particles

Shake-off of micron-sized alumina particles by nanosecond laser-generated surface acoustic wave (SAW) pulses is used to visualize SAW beam propagation on surfaces of semiconductor crystals. Various phenomena in SAW propagation such as reflection from a sample edge, anisotropic diffraction, and beam steering are demonstrated.

Electro-optic beam deflectors for magneto-optic recording heads (abstract)

To make magneto-optic recording more competitive for data storage, the access times for the magneto-optic head must be reduced. By incorporating nonmechanical beam deflection into a split head architecture, fine access times can be reduced considerably and tracking robustness can be improved. Track switching times of ∼10 μs have been reported by Arimoto et al. using a surface acoustic wave beam deflector.1 In the present work, the use of electro-optic deflection techniques is discussed and demonstrated. Potential advantages of electro-optic scanners include lower power consumption and higher optical throughput. To demonstrate the use of an electro-optic beam deflector, an optical system using a commercially manufactured electro-optic deflector has been assembled to detect a signal from a magneto-optic sample. In this system, a 488 nm laser beam is sent through the deflector into a microscope which is used to focus the beam onto the medium. As the beam deflector scans a focused spot across a magnetic stripe domain on a thin film medium, the reflected beam is sent through a differential detection system which detects the change in polarization due to the Kerr effect. In this way, the presence of the domain is detected without mechanical motion. Experimental detection of 0.6 μm wide stripes has been demonstrated using this system. We believe similar beam deflectors in thin film form could significantly impact the performance of magneto-optic recording heads.

Multiple quantum well optical modulator structures using surface acoustic wave induced Stark effect

Multiple-quantum-well (MQW) optical modulator structures using the quantum-confined Stark effect (QCSE) manifested by the application of an electric field induced by a propagating surface acoustic wave (SAW) are proposed. The magnitudes of the parallel E/sub /// and perpendicular E/sub perpendicular to / electric-field components are computed to determine the electroabsorption and change of index of refraction for the AlGaAs-GaAs system. The proposed structures are shown to be less cumbersome than conventional p-i-n configurations used to impress E. In addition, an enhanced performance Bragg modulator/switch which utilizes the QCSE as well as the acoustic phase grating produced by the SAW beam is described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Diffraction effects in surface acoustic wave harmonic generation

Fourier analysis method has been applied to model the diffraction integral of the second harmonic field nonlinearly generated by a surface acoustic wave beam. Cross‐section profiles of the second harmonic field have been calculated at different longitudinal positions along an acoustic beam propagating on a yz‐LINbO3 crystal. Theoretical curves are reported together with experimental results relative to the case of a fundamental wave emitted by a 24‐wavelengths‐wide transducer at the frequency of 35 MHz. A theoretical determination of the energy loss produced by diffraction effects in second harmonic generation is performed by evaluating the acoustic energy of the second harmonic wave over cross sections of the acoustic beam and by normalizing these quantities to the ones relative to plane wave propagation. Diffraction loss in isotropic and anisotropic materials has been calculated as a function of the longitudinal position along the beam axis for different directivities of the source. A generalized diffra...

Nonlinear interaction of surface acoustic waves in waveguide

AbstractA theoretical and experimental study has been conducted on the nonlinear interaction of a surface acoustic wave (SAW) on a surface acoustic waveguide. It is shown theoretically and experimentally that from the parametric mixing phenomenon of two SAW's traveling in the opposite directions, a SAW with the sum frequency is generated which propagates with a certain angle from the waveguide. By changing the frequency difference, the propagation direction of the sum frequency SAW can be controlled freely. the excitation efficiency is such that: (1) it is higher for a narrow waveguide and for a larger velocity variation; and (2) it is periodic with respect to the waveguide width and the period is one wavelength of the sum frequency SAW. Such a generation of the sum frequency SAW and the SAW beam scanning in a plane are possible only with the SAW guided mode. Since the control of the SAW propagation direction in a plane is possible, an application to a two‐dimensional signal processing is conceivable.

A new type of laser probe

A new technique to measure surface acoustic wave beam profiles is described. A measurement is made of the average phase change of the acoustic wave resulting from periodic heating of the sample surface by an incident modulated laser beam. Scanning of the laser beam across the acoustic wave results in a profile of the energy density in the acoustic beam. To measure the phase change, a surface acoustic wave oscillator configuration is used. Possible application of the technique to the measurement of applied and residual surface stress is discussed.

Second-harmonic diffraction field in nonlinear propagation of transversely limited surface acoustic wave beams

The study of the Fresnel field of the second harmonic of a finite width surface acoustic wave, parametrically generated through the nonlinear interaction on a LiNbO3 substrate, is performed both theoretically and experimentally. Theoretically, a model has been developed which computes the acoustic field at each point as given by the sum of all the second-harmonic plane wave fronts nonlinearly generated by the interaction of any two plane wave fronts present in the fundamental wave angular spectrum. Experimentally, a phase contrast optical probing technique has been used, which permits separating the contributions of the second-harmonic field from that of the fundamental wave. Theoretical and experimental transversal amplitude profiles of the surface acoustic wave second-harmonic field are presented, relative to the case of an acoustic beam launched from a 24-wavelength-wide transducer on the free surface of a LiNbO2 sample, at the fundamental frequency of 34.5 MHz.

Efficient three-wavelength-output SAW multistrip beam compressor for convolver applications

The problem of obtaining very narrow surface acoustic wave beams from multistrip compressors is examined experimentally, and a modified geometry is described which allows an extension of previous design methods to narrower output beam compressors, such as required, for example, for direct feeding of a 3λ-wide acoustic waveguide in a monolithic convolver.