Probing of Acoustic Surface Perturbations by Coherent Light

Abstract

The need for sensitive methods of detection and visualization of acoustic surface perturbations has grown with the increasing interest in such fields as acoustic holography, ultrasonic surface wave devices, and acoustic trapped energy resonators. One very sensitive detection method utilizes a coherent light beam as a probe for locally measuring phase and amplitude of the acoustic field. Several variants of this technique are possible, based on measuring phase, deflection, wave front curvature, and spatial frequency content of the reflected beam. Each one of these variants may be combined with a scanning motion of the beam in order to visualize the entire sound field. This paper will attempt to survey the present state of the art and compare the different techniques on the basis of their sensitivity and applicability to specific requirements.

Measurement of evanescent wave properties of a bulk acoustic wave resonator [Letters]

“…Interferometers have gained popularity as the optical detection method of choice and several setups have been published [21][22][23][24][25][26][27][28][29][30][31][32][33].…”

“…Because the history of optical probing of surface vibrations dates back to the 1960s and beyond, there exist several excellent review articles [22,[66][67][68], books [69][70][71][72][73] and book chapters [74][75][76][77][78] on the various optical detection methods.…”

“…This corresponds to a measurement sensitivity of ∼ 2 × 10 −4 nm/ √ Hz. The theoretical detection limit for a heterodyne interferometer (perfect interference, shot noise limited detection) is given by [22,84] By increasing the available laser power incident on the photodetector, the system was improved such that the smallest detectable surface vibration amplitude is now ∼ 0.3 pm, as measured from an actual sample (measurement results reported in Publication IV), with a detection bandwidth of 100 Hz. For these measurements, the scanning speed was ∼ 270 000 pnt/h.…”

Scanning heterodyne laser interferometer for phase-sensitive absolute-amplitude measurements of surface vibrations

“…This corresponds to a measurement sensitivity of ϳ2 ϫ 10 −4 nm/ ͱ Hz. The theoretical detection limit for a heterodyne interferometer ͑perfect interference, shot noise limited detection͒ is given by 10,11 A min = ͱ 2eB…”

Laser Installation for the Measurement of the Acoustic Fields Parameters on the Surface of Acoustic Wave Guides

“…It is one of the best methods for the solutions of many research tasks in the development of the new elements and acousto-electronic devices using SAW. The basics of the heterodyne method are described in [3,4], also it was discussed in review work [5]. Practical realization in different electronic and optical schemes was described in [6][7][8][9][10].…”