Acoustic interferometer

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

Surface wave convolver apparatus

Abstract: Apparatus for convolving acoustic surface waves without dispersion comprising a piezoelectric substrate having surface acoustic waves generated at opposite ends thereof and directed towards an interaction region formed from a semiconductor film deposited thereon. The film is deposited on the substrate at such an angle with respect to the direction of propagation of each of the two acoustic surface waves so that the dispersive components of the wave vectors associated with the surface acoustic waves refracted in the interaction region substantially cancel. Apparatus is also disclosed for substantially eliminating undesired wave reflections in a convolver operating in the degenerate mode wherein a conductive array of electrode fingers is disposed at an angle with respect to the direction of propagation of the acoustic surface waves such that the reflections therefrom are directed away from the paths traversed by said acoustic surface waves.

Fixed Path, Variable Frequency Acoustic Interferometer

Abstract: A fixed path, variable frequency acoustic interferometer is described that is particularly suited for measuring ultrasonic velocities in liquids as a continuous function of temperature and pressure of the medium. The interferometer contains two clamped crystals: one, a low intensity ultrasonic source; and the other, a fixed, parallel reflector. The frequency of excitation, supplied from a frequency generator, is varied, and cyclic changes in input impedance are detected in an impedance bridge circuit. Crystal resonance is avoided. The interferometer, addition to the usual advantages of a fixed path system over a variable path one, operates at very low power levels; hence, it avoids problems occasioned by high intensity pressure waves. Frequency, the measured variable, is one that can be precisely measured with comparative ease.The complete equivalent network for either the fixed or variable path interferometer is presented, from which the operation of the fixed path, variable frequency system is derived. The effect of crystal backing impedance is discussed, and the characteristics of the interferometer are shown to be those of a double crystal interferometer having infinite backing impedance.The velocity of sound in water is measured between 25 and 53°C in the frequency range of 600 to 800 kc. At 25.0°C the measured velocity is 1496.8±0.3 meters/second, and the temperature coefficient is +2.7 meters/second °C.

Measurement of Absorption-Line Profiles with a Fabry–Perot Interferometer*

Abstract: We have calculated the line profiles to be expected when a Fabry–Perot interferometer is used to measure absorption lines. We have shown that large errors may be introduced in the measurement of the integrated absorption, even when an interferometer of high finesse is used. Curves and tables are given for finding the true absorption width and the true peak absorption from the apparent values observed under different operating conditions of the emission light source and the interferometer. We show qualitatively that the distortions are partially due to the presence of nonzero wings in the instrument-bandpass function. Finally, we show a Fourier series expansion of the integral giving the transmittance of the Fabry-Perot interferometer when absorbing atoms are in the light path.