Optical measurements of the self-demodulated displacement and its interpretation in terms of radiation pressure

Abstract

Using a sensitive optical interferometer, the low frequency displacement nonlinearly generated by an ultrasonic tone burst propagating in a liquid is studied. Close to the source, the low frequency displacement contains a quasi-static component, which is affected by diffraction effects farther from the transducer. The experimental setup provides quantitative results, which allow the determination of the nonlinearity parameter of the liquid with a good accuracy. Such measurements are carried out in water and ethanol. Finally, the pressure associated with the low frequency displacement is discussed. Introducing the temporal mean value of the displacement, as already done in lossless solids, the noncumulative part of this second order pressure is associated with the static part of the low frequency displacement. This interpretation leads to extend the definition of the Rayleigh radiation pressure usually introduced for a continuous plane wave radiated in a confined fluid.

Finite-size effects on the quasistatic displacement pulse in a solid specimen with quadratic nonlinearity

“…9(b) are similar to the experimental waveforms observed by R enier et al in water. 6 Until similar measurements are conducted in solids, this good qualitative agreement can be considered as initial experimental proof of the described diffraction effects on the quasistatic displacement pulse.…”

“…Jacob et al 5 conducted displacement measurements with an optical interferometer in fused silica and aluminum alloy samples and found that the quasistatic displacement pulse produced by a longitudinal acoustic wave exhibited a flat-top shape with amplitude independent of the duration of the tone burst, but proportional to the propagation distance. R enier et al 6 also found that the amplitude of the quasistatic displacement generated by an ultrasonic tone burst propagating through water was linearly proportional to the propagation distance. Narasimha et al 7 conducted similar experiments in Al7175-T7351 alloy using a piezoelectric receiver and confirmed that the detected quasistatic pulse exhibited a flat-top shape and its amplitude was independent of the duration of the tone burst.…”

Self-demodulation of high-frequency ultrasound

“…26͒ and 10 MHz. 30 In an accompanying study, for which preliminary results are reported in Ref. 31, the current writers have found that a short ͑ϳ2 cycles͒ ultrasound pulse with a carrier frequency of 10 MHz can excite bubbles having a resonance frequency of about 1 MHz by repeating the pulse at a repetition frequency of 1 MHz.…”