Isotropic media which become anisotropic in the presence of an acoustic wave are demonstrated to act as optical polarizors. In contrast to traditional polarizing plates or rotators, the final state of polarization of light passing through a crystal with ultrasonically induced anisotropy, can smoothly be controlled by varying the acoustic parameters. The main diffraction and polarization effects are visualized in the case of fused quartz and dense flint.

The acousto-optic methods have given valuable insight to the complicated structure of the near field of ultrasonic transducers. Although the image formed is the result of the change of optical path integrated over essentially a thick grating, the results show interesting details. From the early schlieren photographs made with white light to the signals produced by pulses, surprising results are seen.

In recent years there has been a great deal of interest in the use of wavelets to supplement or replace conventional Fourier transform signal processing. This paper provides a review of wavelet transforms for signal processing applications, and discusses several emerging applications which benefit from the advantages of wavelets. The wavelet transform can be implemented as an acousto-optic correlator; perfect reconstruction of digital signals may also be achieved using acousto-optic finite impulse response filter banks. Acousto-optic image correlators are discussed as a potential implementation of the wavelet transform, since a 1D wavelet filter bank may be encoded as a 2D image. We discuss applications of the wavelet transform including nondestructive testing of materials, biomedical applications in the analysis of EEG signals, and interference excision in spread spectrum communication systems. Computer simulations and experimental results for these applications are also provided.

After recalling the pioneers of acousto-optics, the basis of the phase-vector analysis is considered as an introduction to explain the videocassette, which shows, as an animation, some sequences of the graphical integrations of the formula written for an easy calculation of the light-diffraction by more than one beam of progressive ultrasonic waves. The light amplitude of a given diffraction fringe is calculated by integrating the vectorial contributions carried to a given point of the screen by the elementary light blades into which the entering rectangular light beam can be divided. The resulting vector, in addition to the relative light intensity of a fringe gives, by its phase angle, the phase shift of the light amplitude due to the ultrasonic waves, allowing to determine, e.g., the frequency modulation or the frequency shift. Some reported curves show the graphical integrating curves and the animations evidence their evolution in time for some different diffracting arrangements and the eventual amplitude modulation. A symbol is proposed to summarize the physical parameters of the experimental diffracting arrangement when the symbolism of the Bessel functions cannot be applied.

Some equations that couple the amplitudes of transmitted and diffracted light beams interacting in an anisotropic medium with slightly divergent acoustic beam are derived. The acoustic beam is generated in the medium by means of a piezotransducer whose transverse dimensions are bigger in comparison with a sound wavelength. The acoustic beam parameters are defined by the transducer dimensions under the conditions of parabolic equations of sound propagation satisfaction. In the interaction area the incident light beam has a determined polarization and directed parallel to the acoustic beam. The anisotropic diffraction of this beam on sound is accompanied by the appearance of diffracted beam that has the same direction of propagation as the incident one, but polarized orthogonally to the direction of polarization of incident beam. If both light beams satisfy the parabolic equation of propagation, then two first-order equations can be formulated that bound Fourier spectra of transmitted and diffracted light beams and acoustic beam in their interaction region. By solving these two equations at the proper boundary conditions one can acquire the diffracted light beam longitudinal and transversal amplitude distribution. some particular cases of transversal distribution of acoustic and light beams are analyzed. It is shown that the diminishing of cross section of acoustic beam is accompanied by a bandwidth broadening of a transmission of an acousto-optic cell and by a shift of the center of this band relative to the point corresponding to the optimal interaction of the plane acoustic and light waves.

Light-diffraction tomography is a noninvasive measurement technique for mapping ultrasound fields and provides a high spatial resolution. In the range of the Raman-Nath approach, this technique can be successfully applied to frequencies of approximately 5 MHz to ultrasound fields of any geometry. Beyond this frequency range, however, light diffraction implies peculiarities that strongly affect data acquisition. It is the aim of this review to outline the capability of the method, including its range of applicability, and to discuss new steps for its extension.

The basic topic of this work is the theoretical analysis of external stress field influence on the geometry and effectiveness of acousto-optic interaction in isotropic solids. An external field causes changes of medium's optical properties, that is, changes of dielectric permeability tensor components. Because of such changes, an isotropic medium becomes a uniaxial on.e Detailed calculations have been carried out for a BK7 glass in the 10⁴-10⁹ Hz frequency range, for stress of values of 10³-10⁷ N/m. The results of calculations are presented in the form of graphs.

A new method of analysis of light interaction with phase lattices limited in space is offered. The method is based on expansion of fields in spectra on the Kotelnikov-Shannon sampling function. this base system of the functions does not have information redundancy and permits one to define directly the power-generating characteristics of a diffracting light, instead of its complex amplitudes. The scattering field appears quantized. The signal is defined simply by the sum of powers of elementary beams in the received aperture. The absence of redundant information about a phase rather simplifies the solution. The possibilities of the method are illustrated by examples of Bragg's diffraction on coherent sound, transition in scattering with decreased degree of coherency, transition in Raman-Nath regime at decreased thickness of the volume of interaction.

Polarization effects that arise during diffraction of an arbitrarily polarized light by an acoustic wave in an anisotropic medium are studies both theoretically and experimentally. Peculiarities of these effects in the cases of isotropic and anisotropic scattering of the light are considered in detail. Results of polarization state measurements performed with a paratellurite acousto-optic cell in the zeroth order of diffraction are presented as well.

The heterodyne detection of two laser beams offset in frequency is considered. The paper includes all optimization procedures to maximize beat signal in herterodyne experiments of two laser beams shifted in frequency by acousto-optic Bragg cell.

In the ultrasonic light diffraction phenomena in an isotropic medium in the intermediate range (between Raman-Nath and Bragg) variations in polarization state of diffracted light have been predicted and experimentally observed. In the paper some experimental and numerical results for 0 order of light diffracted by ultrasonic wave of 50 MHz frequency are presented. A possibility of continuous control of the polarization state from linear to elliptical or circular against the Raman-Nath parameter has been confirmed in good agreement between theoretical and experimental values.

Light diffraction by ultrasonic waves has been studied for many years, however we still can not say that the phenomenon has been examined completely. During the last decade the near field investigations received a particular attention. The new results obtained, both in the near field and in the far field of ultrasonically difracted light, forced us not only to change our point of view concerning this phenomenon but also to modify the formulas describing it. A brief review is given of some of the results which have been obtained up until now, both theoretical and experimental ones. Some new theoretical suggestions, based on the N-th order approximation (NOA) method are presented.

Some formulas are derived, based on the 1OA (1st order approximation method), which describes the intensity distribution of light diffracted by two spatially separated ultrasonic beams. The anlaytical results obtained for the case v << Q are not only in a good agreement with the previous ones, given by Leroy, Blomme, or Kwiek but, what is more important, they are considerably easier to be interpreted physically. The presence of symmetry and asymmetry in diffraction orders (+ 1st and - 1st) is shown. Explanation is given of the rediffraction effect, discovered by Kwiek and Reibold.

After analyzing the combination of the acousto- and electro-optic effects, two applications are presented. The first is the use of that combination to reduce the tilt sensibility of the acousto- optic devices. The second is related to an interaction configuration that is appropriated to wideband spectrometers.

The experimental results of research of the acousto-electronic interaction are in essence different from prediction of the theory. Instead of the laminarity amplified of the seen noise is formed the moving domain with abnormal properties: its intensity increases superexponentially in the range of 2nd order in nonlinear region, and frequency of maximum of spectrum is smoothly displaced into the region of subharmonic as far as advancement along the sample. It testifies to the absence of essential mechanism from the theory. The experiments have shown, that this mechanism is connected with three-dimensionality of the process of interaction. The critical cross-section of the interaction volume is the radius of coherency of the noise flux. It is shown that amplification of the injected signal with large gain, with dynamic range not less than 50 dB, is possible in the thin channel.

The method of finding Mandelshtam-Brillouin components on observed data is suggested. It is proved a convergence of an algorithm of a minimization is functional. Solutions found are discussed.

We first report an optical image processing technique using acousto-optic Bragg diffraction. Instead of using frequency-plane filters, we demonstrate experimentally the programmable filter characteristic of the acousto-optic cell by changing the peak phase delay (alpha) . High- pass and low-pass filtering can exist simultaneously in different diffracted orders. Furthermore, we demonstrate the use of an acousto-optic device in modeling controllable partically incoherent illumination of phase gratings, or the propagation of images through a random medium with a given power density spectrum.

The history of acoustical imaging is outlined by reference to seven topics. These topics relate in rough chronological order to the developement of various imaging systems and the development and application of optical theory to them. Some commentary is made on the influence of technological developments in other fields and their influence on acoustical imaging. The treatment is not exhaustive because of space limitations; there are more than 20,000 pages of literature on the subject and this is to be summarized in eight. An attempt has been made to present some of the major activity in the field over the last sixty yeras.

The paper presents the results of works on a planar optical amplitude refractometer. On the basis of ion exchange Ag⁺ - Na⁺ in glass, channel lightguide sensors are produced. Further on, they will be masked by an appropriate dielectric layer except for a window, where the sample interacts with the waveguide. A planar structure prepared in this way constitutes the basic element of the planar refractometer. Technological and geometric parameters of structures produced influence refractometer transmission characteristics. In the range of lower values of refractive indexes, sensitivity of the refractometer can be increased if the channel waveguide has the shape of a slowly changing sinusoid.

Acousto-optical parameters in the mixture of the polyvinyl alcohol (PVA) polymers with the modified polyvinyl alcohol (MPA) were investigated as the functions of the MPA content, time of exposure, and temperature. The maximal value of the acousto-optical quality coefficients was reached at the contents of the MPA above 70%. It was proposed to use the PVA photopolymers as the acousto-optical modulators and deflectors. It was unambiguously shown an essential role of the alcohol modifications on the change of the acousto-optical parameters. Simultaneously it was revealed a critical dependence of the acousto-optical coefficients from the thickensses of the samples. The data on the acousto-optical quality correlate with the data obtained by the sound losses in the external electrical field.

Some results of investigation of acousto-optical tunable filtration system base on on calcium molybdate single crystal for arbitray polarized non-collimated optical beams are presented. Design principles of the double channel acousto-optical system to ensure spectral filtration of nonpolarized optical beams are also considered. The device uses the collinear light diffaction on a shear acoustic wave propagating along axis of calcium molybdate single crustal. A passive calcite prism arrangement is used to provide spatial separation of orthogonally polarized parts of an incident optical beam. The transmission function of the collinear acousto- optical cell is not sensitive to divergency of the analyzed radiation. The experimental data of the polarized radiation spectral filtration are also presented.

In this paper recent advances in guided-wave acousto-optic interaction and modeling of SAW devices for high signal processing are presented. SAW devices are extremely attractive for reducing hardware complexity problems and power consumption and improve resolution and efficiency in signal processing operations, involving both acoustical and optical field interaction, or only surface acoustic field propagation.

We demonstrated in this work the possibility of application of the effect of resonant acousto- optical (AO) interaction for the creation of wide band and high efficiency Bragg cells on gigahertz frequencies. The main principle of this effect consists in heat there exists the optimum photon energy (very close to the band gap of semiconductor sample) where the optical absorption is still not big enough but the figure of merit already several times higher in comparison with one when the photon energy is fat from the band gap. We have shown theoretically that the optimization of multilayer thin film piezoelectric transducers allows to create AO Bragg cells (deflectors and modulators) working in resonant conditions and having very high diffraction efficiency (more than 10%) and very wide frequency band (up to 2 GHz). This optimization based on the use of the acoustical matching scheme-asynchronous transform, analogous to one in electrotechnics. Experimental devices represent the cells with crystal plates of GaAs and InP of (100) and (110) cut having the multilayer thin film transducer on the butt-end that has been matched with microstrip transmission line. Characteristics of created AO cells reach: 10% per 1 Watt of electrical power; 2 GHz frequency band with 8 MHz frequency resolution. The obtained experimental results show a good agreement with theoretical predictions.

The paper presents the technology of obtaining planar symmetrical Mach-Zehnder interferometer basing on K⁺ - Na⁺ ion exchange in glass. The influence of technogoical process parameters and interferometer geometry on the optical characteristics has been examined.

Knowledge about optical and thermal properties of tooth tissue is necessary for application and use of new laser techniques in dentistry. Experiments have been carried out with tooth tissue from human and some species of animals at wavelengths reaching from ultraviolet to visible regions, using different spectroscopic methods which give complementary information about the samples. Photothermal spectroscopy, remittance spectroscopy, and fluorescence spectroscopy provide the possibility for differentiation between tooth constituents.

The parallel processing of the information in real time is very important in the field of computing, pattern recognition, and signal processing. Acousto-optical techniques are particularly interesting from these applications point of view, due to the high degree of parallel processing and broad bandwidth inherent in optical systems. The Bragg cell is the extremely versatile device and may act in combination as a variable pitch diffraction grating, optically taped delay line, single side band mixer, light amplitude modulator and sometimes as an optical polarization switch. This gamut of application possibilities has allowed to develop numerous optical architectures and multifunctional acousto-optic facilities.

Nonlinear acoustics have witnessed a tremendous amount of work in the last 40 years. Finite amplitude wave propagation lead to the evaluation of important material parameters, e.g. B/A for liquids and third order elastic constants for solid materials. These quantities are related to nonlinearity of materials. More recent works have utilized the concepts that material inhomogeneities which clearly reduce the strength of materials on the microscopic scale are insensitive to measurements of linear acoustic parameters e.g. velocity, attenuation, or reflection coeffecient etc., but quite sensitive to variation of nonlinearity parameters. Recent work on nonlinear acoustic measurement related to nondestructive evaluation problems and a newly developed acousto-optic technique to measure nonlinearity parameters will be discussed.

The dispersion of surface acoustic waves and the colinear diffration of guided optical modes by the SAW have been studied in proton-exchanged Z-cut lithium noibate. The diffraction of guided modes by the Love waves was observed for the first time in PE:LiNbO₃ optical waveguides. The possibility to measure the waveguide depths and guided mode effective refractive indices using acoustic waves is demonstrated.

For optically resonant systems, the intermodulation amplitudes of the 2nd and 3rd orders in approximation of small diffraction efficiency for the two main AO interaction regimes: 'thin' and 'thick' gratings are for the first time calculated. It is shown, that the photoelastic nonlinearity causes in general case the complexity of intermodulations. However, under certain conditions, the effect of compensated intermodulation can take place. It yields to the possibility of remarkable growth of the dynamic ragne value which is a great importance parameter for many AO devices.

Optical, acoustical, and near-resonance acousto-optical properties of GaAs and InP are investigated and several high performance devices are achieved using these crystals. It is shown that this study can be extended to other direct-gap semiconductors of III-V and II-VI elements to match the optical sources in a large range of available light wavelengths.

This report briefly reviews recent progress in the use of sensors to monitor critical parameters during material processing. The techniques focus on the use of waveguides providing an ultrasonic link between the detector and the part in the furnace.

Peculiarities of light diffraction on ultrasonic waves in glasses and birefringent crystals are examined thoeretically and experimentally. Isotropic dense flint glass material DF-7 and optically anisotropic crystal of tellurium dioxide were chosen for the investigation. The diffraction was observed in intermediate and Bragg regimes of aocusto-optical interaction. From five to seven diffractional maxima in a diffractional pattern were considered in the theoretical research. Intensitites of zero, forst, second, and third diffractional orders were measured during the experiments. Special attention was devoted to analysis of the diffraction in the second diffractional order. Intensities in the second maximum up to 60% in the glass and up to 80% in the crystal were obtained. Applications of the investigated phenomena in acousto-optical devices for scanning and frequency shifting of light are discussed in the paper as well.

We investigated the changes of acousto-optical quality coefficients in olygoethermethacrylate photopolymers of the different chemical contents from temperature. It was revealed that increasing of the aromatic's rings leads to increasing of the acousto-optical quality coefficients M, and only after we have observed the influence of the distances between the C equals O chemical bonds. We also found an increasing of M with the decrease of the temperature below the 80...100 K. The maximal value of the M reaches its value at 4.2 K. The data obtained are in good agreement with previous investigations of the optical second harmonic generation. An essential influence of external electric field on the acousto-optical properties of the mentioned photopolymers was revealed. In our opinion it reflects an essential role of the acentrical quasicrystallines, which give contributions into the piezo-optical constants.

Basing on a 1D model of heat propagation in gas-sample-gas structure, a method for determining thermal properties of plat-like samples is proposed. The method assumes photodeflection detection of photothermal signal. In the method, a signal frequency dependence is measured. It is shown that in high frequency limit, the signal depends only on thermal properties of gas. Excluding the gas contribution to the measured dependence a signal part connected with the sample can be calculated. Fitting theoretical curves to obtained data, one can estimate thermal diffusivity of the sample. Methods for determining thermal diffusivity of gas and distance between a probe beam and the sample surface are also proposed. A good agreemnt between theory and experiment is obtained.

Knowledge about optical and thermal properties of tooth tissue is necessary for application and use of new laser techniques in dentistry. Experiments have been carried out with tooth tissue from human and some species of animals at wavelengths reaching from ultraviolet to visible regions, using different spectroscopic methods which give complementary information about the samples. Photothermal spectroscopy, remittance spectroscopy, and fluorescence spectroscopy provide the possibility for differentiation between tooth constituents.

CdS polycrystalline samples, doped by diffusion with Cu, were examined by photoacoustic spectroscopy. The relatively low dopant solubility Nd equals 2 X 10¹⁸ cm^-3. This supports the suggestion that the well-known problem with the achievement of good conductivity in wide-band-gap semiconductors should be associated with the lack of good dopant solubility in the material.

This paper presents results of the initial stage of investigations concerning the application of photoacoustic spectroscopy technique as a tool for evaluation of lubricating oil degradation degree during its use. Absorbance spectra in 200 divided by 800 nm range and photoacoustic signal spectra in visible range have been determined for two oil samples: the new one and after oxidation during specified time interval (oil wear simulation). Both analysis methods led to similar results indicating the most tangible difference between samples to be found in the exicting light wavelength range below 450 nm.

In this paper some groups of intensity fiber optic temperature sensors are presented. The physical idea and construction of bending, semiconductor, and luminescence sensors are described. The sensor on the base of thermal radiation effect is presented, too. In the sensors the multimode fiber optics were applied. Potential applications of this type of sensors in power engineering and chemical industry are discussed.

The microstructure of bone is described and formulas are presented, which give us opportunities to assess the mechanical properties in this range. The scanning acoustic microscope is used to image the mechanical structure and to measure the averaged sound velocity of in vitro samples of human bone. It is possible to assess the attenuation of sound waves. The confocal laser scanning microscope use similar principles. By both microscopes the confocal scanning procedure is applied and an example of specimen is imaged. The pictures are shown and their content is discussed and compared. The information about the object structure shows differences depending on the method used.

Bonding of silicon wafers is a method that is widely used in microsystem technology. To quantify the quality of the bond only IR interference techniques which are restricted to vertical sizes of voids <EQ 250 nm have been applied up to now. The new idea is to use acoustic microscopy for the examination of these bonds. In order to be able to evaluate the possibilities and limitations of such a method we worked out a preparation technique to investigate bonded silicon wafers with defined etched structures. Etched wafers were bonded to nonetched wafers, chips of 10 X 15 mm² size were sawed out of the wafer pair followed by grinding and polishing these structures under small angles of 34 feet to 3 degrees. With working frequencies of 200 MHz and 400 MHz we obtained good results with structures that have a height of 50 nm and a horizontal size of some micrometers. It was possible to show structures that were covered with a silicon layer that is 70 micrometers thick. Additionally wafer pairs with metallic interlayers were investigated. The results are compared with images taken with an IR transmission optical microscope.

Usually the acoustic field at the back side of a sapphire lens in a scanning acoustic microscope is calculated considering a transducer that is not shifted relative to the optical axis. In a simple model these calculations were modified by taking a parallel shift of the circular transducer into account. With this modified acoustic field at the back side of the lens the V(z) curve for an ideal reflector and for a material which properties are similar to those of aluminium is calculated. These simulations are used for a qualitative analysis of the influence of a transducer shift on V(z) measurement.

The fluorocarbons liquids are studied by acoustical method and Brillouin scattering in temperature range from 273 to 313 K and pressure from 0.1 to 50 MPa. Acoustical relaxation in liquid C₈F₁₆ with relaxation time of order 10^-10 s is discovered. This acoustical relaxation has been analyzed under an assumption of a single vibration relaxation. The measurement of hypersonic velocity by means of Mandelshtam-Brillouin light scattering under high pressure was conducted within two angles of light scattering.

By means of acoustic spectroscopy technique there was investigated acoustic relaxation of vibrational type in liquid diiodemethane and methyliodide within the range of pressures 0.1 to 100 MPa and under temperature T equals 293 K.

Aqueous solutions of the salts of alkylphosphoric acid are studied by acoustic method. The measuerments of the ultrasound's velocity V and density (rho) in aqueous solutions of CINTAF-108H at temperature ranges from 283 to 313 K and concentration intervals 0.15 to 0.3 kg/m³ were carried out. The data of critical micelle concentration and thermodynamic parameters are determined.

Ultrasonic velocity and density in water solutions of lauril sodium sulphate at frequency 36 MHz, within the range of pressures from 0.1 to 105 MPa at temperature T equals 293 K were measured. According to data of ultrasonic velocity and density under high pressures there was calculated adiabatic compressibility in objects studied from pressure. It was found out that the region of critical concentration of micelle formation has been shifted to the zone of much more low concentrations.

The kinetics of micelle formation of the binary mixture of the ionic and nonionic surfactants-- carboxymethylated neonol AF₉-6CM (72,7%) and neonol AF₉-6 (18,1%)--in aqueous solutions have been investigated using the ultrasonic relaxation technique. The dependence of the reciprocal relaxational time against total concentration of surfactant shows that minimum exists. And this minimum corresponds to the critical micelle concentration (CMC). The thermodynamic parameters of micelle formation have been estimated using the kinetic data. The minimum at the temperature dependence of CMC have been observed and it has been explained by the changes of the thermodynamic functions of micelle formation.

The study of the pressure dependence of the velosity and coefficient absorption of ultrasonic waves at two complex polyethers and mineral oil is reviewed. Acoustical parameters were measured in the frequency range 3-27 MHz and interval of temperatures from 223 to 313 K and at pressure from 0, 1 to 150 MPa. It was found that pressure dependence of velosity is nonlinear and reduces at low temperature. The value increases with pressure and attains the maximum with cooling of liquids. The temperature of maximum attenuation of longitudinal waves increases with increasing pressure at a rate of dT/dP equals 0,0103-0,019 K/bar. By comparison temperature dependence acoustic parameters obtained for different regimes of isobar cooling with following throw off pressure in the glassy state effect have been discovered, which gets the name of temperature-pressure hysteresis.

Propagation of acoustic waves in turbulent media has been studied within the approximation of optical geometry. The standard deviation (sigma) _R of fluctuations in the horizontal shift of a wave ray relative to the observation point has been estimated in dependence on the distance r_o between the source of a wave and the point of observation, the angle $qq of the ray emission by the source, the mean square fluctuations in the acoustic refractive index of turbulent medium and on the autocorrelation function of refractive index fluctuations. The calculations have been performed for the Gaussian correlation function, the simple exponential one and the von Karman correlation function. It has been stated that in the case of simple exponential correlation function (sigma) _R is larger than for the Gaussian one if r_o/l >= 4. In the case of von Karman medium inhomogeneities correlation function, values of (sigma) _R increase with increasing in values of parameter v of the von Karman function.

Extensive measurements of the velocity C and absorption coefficient (alpha) of the longitudinal waves have been made at temperatures in the range 243 to 363 K and frequency from 10 to 90 MHz in five samples of mineral oils with a different percentage concentration of nonwear additive MKPh-18Y: MG-8A, containing 0.3% additive; MG-8A, containing 2% additive; I- 20; I-20, containing 1% additive. The tribologic properties (anti-friction and anti-wear) these samples have been studied on a four-ball pilot friction unit. The adding the anti-wear additive have changed the viscoelastic properties of mineral oil essentially. The generalized estimation of the influence of the additive on lubricant property showed that the samples with greater values of bulk viscosity and width of relaxation times distribution had the better anti-wear characteristic, but worse anti-friction properties.

Ultrasonic investigations are carried out in aqueous solutions of organic dyes, methyl violet, and methlene blue to study the behavior of these dyes in aqueous binary mixtures formed with methanol, formamide, and dimethyl formamide as solutes in a water-rich region. The sound velocities are evaluated using a single crystal variable path interferometer working at 1 MHz with an accuracy of +/- 0.003%. The densities are measured using a Pycnometer and velocities with an Ostwald's viscometer. The various acoustical and thermodynamic parameters are evaluated using experimental solutions. An attempt has also been made to evaluate the excess thermodynamic functions like excess molar volume and excess compressibility in the binary mixtures and hence study the nature of molecular interactions of the dye compounds with different interactions the dye compounds on water structure in presence of different solutes in a water-rich region.