Available online at www.sciencedirect.com ScienceDirect Physics Procedia 70 (2015) 253 – 257 2015 International Congress on Ultrasonics, 2015 ICU Metz Acousto-Optics as an Efficient Method for Physical Measurements Sergei V Kulakova*, Olga L Balyshevaa, Arcenii Yu Zhdanovb, Victor V Kludzina, Oleg V Shakina a St Petersburg State University of Aerospace Instumentation 67, B Morskaya Str 190000 St Petersburg, Russian Federation b University of South Florida, 4202 E Fowler Ave, Tampa, FL 33620, United States Abstract In addition to acousto-optic information processing and manufacturing of such devices, the interaction between optical and acoustic waves are an efficient method for physical measurements The paper analyses the potential of the acousto-optic method for measurement and investigation of crystal properties It also presents some examples of this method applied to such measurements and investigations The acousto-optic implementation of the pulse-phase method is used for acoustic velocity measurements Velocities in an arbitrary directions can be measured using the Shaefer-Bergman method (the visualization of the angular distribution of the inverse phase velocities) together with the pulse-phase method The matrices of crystal elastic coefficients can be evaluated using the Shaefer-Bergman patterns, using the minimum number of tested samples The Schlieren (shadow) image method can give information both on the characteristics of acoustic and optical fields The acousto-optic interaction is Efficient Method for determination of elastic material nonlinearity parameters © Published by Elsevier B.V.B.V This is an open access article under the CC BY-NC-ND license © 2015 2015The TheAuthors Authors Published by Elsevier (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-reviewunder under responsibility of Scientific the Scientific Committee 2015 ICU Metz Peer-review responsibility of the Committee of ICUof2015 Keywords: acousto-optics; Shaefer-Bergman method; Schlierens images; measurements * Corresponding author Tel.: +79219492098; fax: +78127084204 E-mail address: SVK25@mail.ru 1875-3892 © 2015 The Authors Published by Elsevier B.V This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the Scientific Committee of ICU 2015 doi:10.1016/j.phpro.2015.08.148 254 Sergei V Kulakov et al / Physics Procedia 70 (2015) 253 – 257 Introduction Mechanical perturbations in media are visualized using optical components since early XIX century in works of Scottish physicist D Brewster Later, a new area of acousto optics was created based on that It describes and utilizes optical and acoustic waves’ interaction in different media Since the beginning of the XX century nature and technology excitation and transmission of sound waves through the material, as well as the interaction of sound waves with light have become an important area of research with many practical applications In 1921 Brillouin predicted that the ultrasonic waves in ideal fluid behave like a diffraction grating for light [1] His result was confirmed by Debay and Sears in 1934 [2] In the future, Schaefer and Bergmann [3,4] demonstrated the diffraction of light by acoustic waves in crystals This interaction may be used as an affective mean for different measurements It allows measurement of the following physical fields’ properties: electromagnetic nature (of optical) and mechanical nature (of acoustic), interaction media properties, orientation parameters of experimental device structure and complex radiosignal parameters Possibilities and features of acousto optic measurements are defined by the diffraction ratio sin θ = λf V , where ș – angle between direction of incident and diffracted light rays, Ȝ – wavelength of interactive fragment of input optical signal, f – frequency of acoustic modulation signal, V – velocity of acoustic wave propagation (media property) Each of these ratio parameters can be fixed and measured if other parameters are determined: (Ȝ) – changing spectral components of optical radiation using acousto optic spectrometers based on different constructions, including unique collinear and quasi-collinear forms of acousto optic interactions in crystal; (f) – classical variant of measurement instantaneous spectra of a succession of radio signals in chosen range using acousto optic spectra analyzers in parallel (panoramic) mode; (V) – an extensive set of methods and devices for visualization and measurement of the acoustic properties of the environment and the interaction of acoustic waves of different types, some of these methods are most effective, if not the only; (ș) – measuring the orientation, for example, determining (bearing) of the angle of arrival of the coherent optical signal (of known wavelength) in a predetermined plane Apparently, this includes high-precision deflection of laser beams through the acousto-optic deflectors, including XY Acousto-optic interaction in crystals is an efficient, reliable and accurate tool for the study and measurement of the elastic characteristics and parameters of the investigated materials Specific properties of crystals determine the characteristic requirements for consistent procedures research The level of diffraction orders arising during the diffraction process, determines the sensitivity and the possibility of measurement processes For the acoustic fields, the following measurements are possible: acoustic mode velocities for selected propagation directions and crystal planes, conditions for acoustic mode attenuation, reflection, refraction, and transformation, their diffractional effects The acousto-optic implementation of the pulse-phase method is used for acoustic velocity measurements Velocities in an arbitrary directions can be measured using the Shaeffer-Bergman method (the visualization of the angular distribution of the inverse phase velocities) together with the pulse-phase method.The matrices of crystal elastic coefficients can be evaluated using the Shaeffer-Bergman patterns, using the minimum number of tested samples The Schlieren (shadow) image method can give information both on the characteristics of acoustic and optical fields An accurate estimation of sample optical homogeneity can be performed using those images This estimation is very important when investigating the quality and growth features for multi-component crystal samples The parameters and characteristics of optical fields can be determined using the acousto-optic spectrometry bases on a dynamic diffraction grid For the interaction medium, this method can show the anisotropy of its properties, qualitatively and quantitatively estimate its collimation properties, measure the angle between the power transfer and wave front directions, characteristics and parameters of elastic non-linearity Using the Shaeffer-Bergman patterns, complex crystallographic cuts can be correctly oriented Sergei V Kulakov et al / Physics Procedia 70 (2015) 253 – 257 Acousto-optical methods for measuring the phase velocity of acoustic waves in crystals Acousto-optical method allows the measurement of the velocity of propagation of acoustic modes in the selected areas and even planes of the crystal The most accurate method for measuring the velocity of acoustic modes (pulse phase) can be implemented in the acousto-optical version under certain conditions In addition, the possibility of optical imaging of acoustic modes reverse speeds angular distributions for the selected observation planes, which makes it possible to obtain a complete set of elastic moduli of the crystal using the minimum number of samples Acousto-optical implementation of pulse-phase method for measuring the delay is the most accurate of all existing and involves the use of a sample with plane faces In the diffraction order a sequence of pulses corresponding to the successive reflections of the acoustic signal from the faces of the sample is formed Angular velocity distribution in crystals (Schaeffer-Bergman images) Acousto-optical imaging technique of the angular distribution of the slowness in selected planes of the crystal (the so-called method of Schaeffer-Bergman images) [5-7] is very informative Schaeffer and Bergman in [3] proposed and developed in a number of subsequent studies [8-12] method for the determination of the elastic constants of transparent crystals, diffraction of light by ultrasound In [3] for the first time shown the twodimensional diffraction patterns for quartz crystals The method is based on optical visualization of crystals existing in the acoustic mode and in such directions that are possible for a given crystal lattice It is known, that methods for measuring the elastic constants are divided into static and dynamic (mainly for monocrystals [13] Among the second group of techniques is Schafer - Bergman method which is substantially optical, since measurements performed by an optical diffraction pattern It can also be considered as an acoustooptic, because it uses the interaction of acoustic and optical waves Note that pulse measurement method is considered to radio communications [13,14] Using the Schafer - Bergman method wavelength of ultrasonic waves propagating in the light-transmitting solids and liquids can be measured from the diffraction pattern of monochromatic light on standing or propagating wave For measuring the elastic constants of single crystals, the sample is required to be a cube to one of the faces of which attached a quartz crystal with a high resonant frequency Schaeffer and Bergman were researching diffraction pattern in liquids and glasses In the case of an isotropic medium, the transmitted light forms a diffraction pattern as two concentric rings formed by individual points of light (spots) Radially inner ring is determined by the wavelength of the longitudinal waves; radius of the external - by the wavelength of the lateral For anisotropic media diffraction pattern consists of three closed curves, which determines the type of symmetry of the lattice along the direction of light propagation The values of the elastic constants can be determined by the radius of the curves at a known frequency, density, dimensions and orientation of the test sample [13] The resulting diffraction pattern is not dependent on the shape of the oscillating body (in the form of a cube, parallelepiped, cylinder or prism), since the wavelength is negligible in comparison with the size of the sample Each light spot in the diffraction pattern is associated with a particular mode and its own direction] Measuring the elastic constants by Schaeffer and Bergman method requires one sample in the form of a cube whose faces are oriented along the crystallographic axes of the crystal Light beam perpendicular to the face of the cube forms a diffraction pattern upon which all the elastic constants [4] The sample crystal formed and manufactured in such a way as to ensure the maximum possible number of acoustic reflections oriented in random directions in a plane normal to the direction of the incident light beam In this case, there may be a two-dimensional diffraction pattern corresponding to the angular distribution of the slowness of the acoustic mode in the selected plane As an example, the presented Schaeffer-Bergman image for selected sections of KRS-5, PbMoO4, TeO2 fig.1,2,3 Figure shows the multiplicative Schaeffer-Bergman image to the main plane of the crystal KRS-5, having a high coefficient of acousto-optic Q-factor (M2) Figure shows a similar pattern to the crystal PbMoO4, and crystals of symmetry (4/m) distribution reverse speeds to determine the direction of extreme speed "clean" modes, respectively, and sign the elastic constant C14 Figure represents the angular velocity distribution for the shear mode in the (001) plane of the crystal prospective tellurium dioxide (TeO2) Characteristic luminosity filling pattern for almost all destinations in the (001) plane of the crystal is caused by a large diffraction-limited for the acoustic mode 255 256 Sergei V Kulakov et al / Physics Procedia 70 (2015) 253 – 257 Fig.1 The angular distributions of the slowness of the longitudinal and transverse acoustic modes in the (001) plane of the crystal KRS-5 (TlBr-TlI) Fig.3 Distribution of velocities of shear inverse modes of (001) plane of the crystal of tellurium dioxide (TeO2) Fig.2 Angular distribution of inverse velocities of longitudinal and transverse acoustic modes in the (001) plane of the lead molybdate crystal (PbMoO4) Fig.4 The structure of the longitudinal mode in the crystal of bismuth germanate Now, if you use the speed reference to the principal axes of the crystal, which were measured by pulse-phase method, it is possible to determine the speed in any direction in a given plane This method allows us to calculate all the components of the matrix of the elastic moduli of the crystal using the minimum number of samples (for the crystal symmetry is not too low, usually samples is enough) The optical structure of acoustic fields’ visualization Acousto-optic interaction allows visually detect features of the propagation of acoustic waves and structure The method of “shadow images” (Schlieren images) has a high sensitivity, allows the accumulation of optical signal and post detector processing In this case the following can be visually and quantitatively determined by the attenuation of the acoustic wave - the effects of diffraction divergence (a measure of the energy divergence), the conditions of reflection, refraction and transformation of acoustic modes, as well as vector deflection parameters of energy transfer from the wave normal The same method can be used for qualitative evaluation of the optical homogeneity of the samples of multi-component crystals Figure shows the "shadow" image visualizing the structure of the longitudinal acoustic wave propagation in the [111] direction of a cubic crystal of bismuth germanate (Bi12GeO20), and the aperture of the acoustic source was ~ 10Ȝɚ Sergei V Kulakov et al / Physics Procedia 70 (2015) 253 – 257 Conclusion Optical and acoustic sources together with a medium of efficient interaction are required to use the acoustooptic method Acousto-optical method allows the measurement of the velocity of propagation of acoustic modes in the selected areas and even planes of the crystal The most accurate method for measuring the velocity of acoustic modes (pulse phase) can be implemented in the acousto-optical version under certain conditions In addition, the possibility of optical imaging of acoustic modes reverse speeds angular distributions for the selected observation planes, which makes it possible to obtain a complete set of elastic moduli of the crystal using the minimum number of samples Unique visual method is an acousto-optic imaging technique based on Schlierens images method In this case, the recorded acoustic waves spatial inhomogeneity effects of divergence and deflection propagation direction of the wave normal Using the properties of elastic anisotropy of crystals can be found direction in which the acoustic wave will have a small divergence (collimating direction) Testing and evaluation of the quality of collimation selected events is most effective by using Schlierens images Generally, such advantages as technically simple implementation, reliability, clearness, self-descriptiveness, and non-destructive nature of the acousto-optic method prevail over some limitations as to applicability to transparent crystals and some preliminary auxiliary measurements The work was financially supported by RFBR grants ʋ13-07-00225Ⱥ, ʋ15-07-04612Ⱥ References Brillouin L Ann de Physique, 1921, v 17, 102 Debay P and Sears F.W Scattering of light by supersonic waves Proc Nat Acad Sci Wash., 1932 V 18, 409 Schaefer C., and Bergmann L., New diffraction effect with oscillating crystals, Naturwissenschaften 22, 685-690 (1934) (In Germany) Bergman L Ultrasound and its use in science and engineering (Moscow) 1957 P 647 Gusev O.B., Kludzin V.V, Acousto optic measurements, Len Univer (In Russia) 1987 Design and fabrication of acousto-optic devices Ed by A.P.Goudzolis, D.R.Pape, S.V.Kulakov NY, Marcel Dekker, 1994 Balakshy V.I., Parygin V.N, Cirkov L.E Physical basics of acousto optics, Radio and communication.(In Russia) 1985 Schaefer, C., and Bergmann, L., Zur Frage der optischen Beugungserscheinungen an schwingenden Glaskorpern Naturwissenschaften 23, 799-800 (1935) (In Germany) Schaefer CI., Bergmann L., Un nuovo metodo ottico per la determinazione delle costanti elastische dei cristalli, Rend Ace Naz Lincei (6), 21, 701 1935 10 Schaefer CI., Bergmann L., Optische Beugungserscheinungen an schwingenden Kristallen im reflektierten Licht, Experimenteller Teil, Sitz.-Ber Berl Akad Wiss Phys math Kl XX, 245, 1936 11 Sɫhaefer C., Bergmann L., Goeh1iɫhH J Die Bestimmung der elastischen Konstanten optischer Glaser mittels der Lichtbeugung an Ultraschallwellen, Glastechn Ber., 1937 12 Schaefer C., Bergmann L., Die Bestimmung der elastischen Konstanten optischer Glaser aus der Lichtbeugung an hochfrequent schwingen- den Glaswiirfeln, Ann d Phys (6), 1948 13 G Hantington Elastic contants of crystals (In Russia) Advances in physical Sciences Ɍ.LXXIV, 1961, pp 303-352 14 Andreev I.A Anisotropy and dispersion of velocity and attenuation of elastic waves in piezoelectric crystals (In Russia) 2006, pp 27-43 257 ... collinear and quasi-collinear forms of acousto optic interactions in crystal; (f) – classical variant of measurement instantaneous spectra of a succession of radio signals in chosen range using acousto. .. techniques is Schafer - Bergman method which is substantially optical, since measurements performed by an optical diffraction pattern It can also be considered as an acoustooptic, because it uses... interaction may be used as an affective mean for different measurements It allows measurement of the following physical fields’ properties: electromagnetic nature (of optical) and mechanical nature (of