Acoustic interferometer

About: Acoustic interferometer is a research topic. Over the lifetime, 1493 publications have been published within this topic receiving 19355 citations.

Diffraction divergence of SH 0 wave in thin piezoelectric plate of lithium niobate

Abstract: By present time the profiles of aperture of Rayleigh surface acoustic wave (SAW) launching by interdigital transducers (IDTs) set on the surface of the wave-guide have been investigated in details. It has been shown that the SAW profile strongly depends on geometry of IDT and when moving off transducer the beam profile changes its shape. Recently the great interest of researchers was caused by acoustic waves in piezoelectric plates due to some advantages compared to surface acoustic waves. It has been also found that these waves are characterized by more values of angle between phase and group velocities (PFA). Plate waves may be effectively launched and received by IDTs. But the profiles of these waves along aperture were not investigated. This paper is devoted to experimental study of profiles of acoustic SH0 waves with shear-horizontal polarization, which propagates in piezoelectric plate of Y-X+220 lithium niobate. The profiles were studied by electrical probe set on the special precision mechanism, which allowed moving the probe in two directions. Because the wave was piezoactive it accompanied by alternating in time electrical field, which was detected by measuring probe. As a result the distribution of amplitude of electric field at different distances from launching IDT was measured. The measurement has shown that the profiles of SH0 wave significantly differ from ones of SAW. These profiles practically keep their shape at different distances from transducer but their amplitude and width change. The comparison with theoretical results showed their satisfactory compliance.

Resonant interaction of standing acoustic waves with a spin system

Abstract: A theory is developed of the reaction of a spin system to a resonant action of an acoustic field and an electromagnetic field. It is shown that it is important to allow for the coherent properties of the acoustic field that excites the spin system both for the calculation of the line profile of direct acoustic absorption and for the line profile of saturation of paramagnetic resonance by sound. By studying the influence of the acoustic field on the profile of the absorption line of rf power it becomes possible to determine the magnitude and sign of the spin-phonon interaction constant.

Interior vs. Exterior Creeping Waves in Acoustic Resonance Scattering

Abstract: In acoustic scattering from elastic objects, resonance features occur in the returned echo at frequencies where the object's eigenfrequencies are located, which are explained by the excitation of interior creeping waves. Correspond- ing resonance terms may be split off from the total scattering amplitude, leaving behind an apparently nonresonant background amplitude. This is demon- strated for spheres, and also for scatterers of arbitrary geometry, using the T-matrix approach. It is shown sub- sequently that the background amplitude can be split further into specularly reflected and geometrically transmitted contributions, plus highly attentuated resonance terms which are explained by the excitation of exterior (Franz-type) creeping waves.

Multichannel interferometry

Abstract: waveslinch gives 90% of the response of an ideally flat mirror. To isolate the laser from the interferometer, and to provide means for varying the beam balance in the two legs, a polarizing beam splitter (PBS) with a quarter wave plate in each leg of the interferometer is used. The polarization angle of the incident beam is varied to change the beam balance. A second PBS is used to analyze the interference. By using both outputs from this second PBS, which has a 180” relative phase shift, the response is doubled and common mode noise is minimized. This system, with associated electronics and display circuitry, has been used to measure and display ultrasonic waves, and some examples are given. It is being used to measure ultrasonic transducer response, to measure and display the interaction between biologic tissue and ultrasound, and as an aid in the design of ultrasonic lenses. In this paper we want to stress the optical design of the system and discuss other applications in the measurement of small motions of mechanical objects.