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Basing on dilatometric and optical anisotropy studies, we have obtained (x, T)-phase diagram for TlIn(S1–xSex)2 solid solutions in the range 0 ≤ × ≤ 0.25 of selenium concentrations. It has been fou...

We determine full matrices of piezo-optic and elasto-optic coefficients for lead germanate crystals

Based on experimental studies of acoustic wave velocities in TlInSe2 crystals, all components of their elastic stiffness and compliance tensors are determined. TlInSe2 has three acoustic ax...

We analyse anisotropy of acousto–optic figure of merit (AOFM) for Li2B4O7 crystals in order to estimate the prospects of these crystals in acousto–optics. We find that the maximal AOFM, 3.44 × 10−1...

In the present work, we analyze acousto-optic (AO) interactions between acoustic waves (AW) and circularly polarized optical eigenwaves in gyrotropic crystals. We find that the AO diffraction of circularly polarized eigenwaves can be divided into six different interaction types. Contrary to the AO interactions analyzed earlier for the case of linearly polarized optical eigenwaves, we distinguish three isotropic interaction types and three anisotropic ones. Moreover, unlike the isotropic AO interactions of linearly polarized eigenwaves of n o - n o and n e - n e interaction types, the effective elasto-optic coefficient (EEC) in the case of interactions between circularly polarized eigenwaves does not depend on the sign of an incident circular optical wave. The anisotropy of the EEC and AO figure of merit is analyzed for a particular case of lead germanate crystals, P b 5 G e 3 O 11 . We demonstrate that the maximal AO figures of merit are achieved for type I isotropic diffraction at the quasi-longitudinal AW. Our calculations are confirmed by the experimental data obtained for the EEC using the Dixon–Cohen method. The experiment is concerned with the AO interactions of circular eigenwaves in P b 5 G e 3 O 11 .

We determine full matrices of piezo-optic and elasto-optic coefficients for lead germanate crystals, P b 5 G e 3 O 11 , using Dixon–Cohen and interferometric methods. Two different types of samples are studied, single- and multi-domain. We show that the correct data for the P b 5 G e 3 O 11 crystals can be obtained only with single-domain samples, since the domain structure induces a number of features that make the final results unreliable. We demonstrate that the acousto-optic figures of merit reach high-enough values at the isotropic acousto-optic interactions with longitudinal acoustic waves propagating along the principal x and z axes ( 63 × 10 − 15 and 37 × 10 − 15 s 3 / k g ), respectively. At the same time, the efficiency of the acousto-optic interactions with transverse acoustic waves is low. The same is true concerning anisotropic acousto-optic diffraction, since the appropriate elasto-optic coefficients are small enough.

We analyze the effect of acoustic wave (AW) polarization states deviation from purely longitudinal and transverse on the anisotropy of the acousto-optic (AO) figure of merit for the case of AO interactions occurring in the principal crystallographic planes. In particular, we obtain phenomenological relations that describe the effective elasto-optic coefficient for the six types of AO interactions, which exhaust all of the possible isotropic AO diffractions. These relations are compared for the alternative cases when the deviations of polarization of the AWs from purely longitudinal and transverse ones are either taken into consideration or completely neglected. Our analysis carried out on the example of

Complete matrices of piezo-optic and elasto-optic tensors are experimentally determined for Tl

We report the results of comprehensive studies of the piezo-optic and elasto-optic effects in lithium tetraborate crystals, Li2B4O7. The full matrices of piezo-optic and elasto-optic coefficients are obtained using a recently developed method based on four-point bending. On this basis, we have estimated the acousto-optic figure of merit for Li2B4O7.

We develop a technique for analyzing the anisotropy of an acousto-optic figure of merit for crystals belonging to tetragonal symmetry groups 4/m, 4, and 4¯. The technique is based on phenomenological relations that describe anisotropies of the effective elasto-optic coefficients and the acoustic wave velocities. Our approach is verified on the example of NaBi(MoO

We have developed a method for the analysis of anisotropy of an acousto-optic figure of merit (AOFM), which is valid for the case of anisotropic diffraction in the trigonal crystals of the point symmetries 3m, 32, and 3¯m. The method is verified via the example of LiNbO

We report on the studies for temperature dependences of elastic stiffness coefficients in Sn 2 P 2 S 6 crystals. Basing on the construction of acoustic velocity surfaces, we have determined the parameters of the slowest acoustic wave that propagates in Sn 2 P 2 S 6 crystals. The acoustooptic figure of merit for the case of acoustooptic interaction with this wave is estimated as ∼0.8 × 10 −12 s 3 /kg. We have shown that Sn 2 P 2 S 6 is very close to the conditions of tricritical point on the ( x , T )- and ( p , T )-phase diagrams of the solid solutions Sn 2 P 2 (Se x S 1− x ) 6 . The critical exponent α of the heat capacity for the Sn 2 P 2 S 6 crystals is equal to 0.42 ± 0.03.

On the basis of combined studies of the acoustic and optical properties of Sn2P2(Se x S1– x )6 solid solutions with x = 0 and 0.28 it is shown that two special points exist on the x,T-phase diagram of these ferroelectric crystals, a tricritical point and a triple one. With increasing Se concentration, the phase transition changes its character at x ≈ 0.28 from second-order to first-order. The phase transition becomes split at x ≈ 0.4, with the appearance of an intermediate incommensurate phase.

Using studies of the temperature dependence of the acoustic wave velocity at high hydrostatic pressures, a tricritical point where second-order phase transitions change to first-order ones was experimentally revealed on the pressure–temperature phase diagram of Sn2P2S6 crystals. The behavior of the acoustic wave velocity is explained in the framework of mean-field theory.

Based on the results for temperature dependences of optical birefringence and optical indicatrix rotation derived for Sn2P2S6 crystals, we show that at the atmospheric pressure, those crystals are under the conditions of tricritical point, with the critical exponent of the order parameter . At the same time, we have found that the temperature behaviour of the rotation angle of spontaneous electric polarization obeys the law . The action of hydrostatic pressure leads to only small changes in the critical exponent β, thus suggesting that the tricritical point on the P, T-diagram of Sn2P2S6 should occur in the pressure range .

A phase transition in Sn2P2(Se0.28S0.72)6 crystals is studied by an optical polarimetric technique. It is proved that this transition is of a second order. The results are discussed with taking into account a possibility for existence of a Lifshitz point in the x, T phase diagram of Sn2P2(SexS1-x)6 solid solutions. It is shown that the temperature-induced rotation of spontaneous electric polarization vector affects essentially the accuracy for the critical exponent of the order parameter determined for the monoclinic Sn2P2(Se0.28S0.72)6 crystals basing on the optical birefringence and thermal expansion studies.

An experimental study and analysis is presented of the acoustic properties of Sn2P2(Se0.28S0.72)6 ferroelectric crystals. Complete matrices of elastic stiffness and compliance as well as characteristic acoustic slowness surfaces have been obtained. The directions of propagation and polarisation of the slowest acoustic waves were determined. It was found that the elastic properties and the acoustic wave velocities for Sn2P2(Se0.28S0.72)6 and Sn2P2S6 crystals are almost the same at room temperature.

We analyze the effect of acoustic wave (AW) polarization states deviation from purely longitudinal and transverse on the anisotropy of the acousto-optic (AO) figure of merit for the case of AO interactions occurring in the principal crystallographic planes. In particular, we obtain phenomenological relations that describe the effective elasto-optic coefficient for the six types of AO interactions, which exhaust all of the possible isotropic AO diffractions. These relations are compared for the alternative cases when the deviations of polarization of the AWs from purely longitudinal and transverse ones are either taken into consideration or completely neglected. Our analysis carried out on the example of Tl3AsS4 crystals reveals that the deviation of AW polarization from its pure states influences the anisotropy of the AO figure of merit only when the AO interactions with quasi-transverse AWs are dealt with. This fact is caused by the peculiar acoustic and elasto-optic properties of Tl3AsS4. On the other hand, the situation can become different for other crystalline materials, where the angular dependences of the AO figure of merit can differ significantly in cases in which the deviation angle increases. This holds true for the AO interactions with both quasi-transverse and quasi-longitudinal AWs. Under these conditions, non-orthogonality of the AWs (or deviation from their longitudinal polarization states) affects essentially the AO characteristics. Finally, we determine the geometries of AO interactions for which the highest AO figures of merit are reached for the Tl3AsS4 crystals.

In the present work, we have experimentally studied and analysed the dilatometric properties of Sn2P2(Se0.28S0.72)6 crystals during ferroelectric phase transition. A complete matrix of thermal expansion tensors as well as the characteristic surface of the thermal expansion tensor has been obtained. The critical exponent for the volume thermal expansion coefficient in Sn2P2(Se0.28S0.72)6 crystals has been determined to be equal to 0.50 ± 0.06, which is peculiar to tricritical behaviour. Non-agreement in the values of the critical exponents evaluated from the temperature dependencies of relative elongation (0.17 ± 0.01) and volume thermal expansion coefficient (0.50 ± 0.06) is shown to be due to the possible temperature rotation of the spontaneous polarisation vector.

Complete matrices of piezo-optic and elasto-optic tensors are experimentally determined for Tl3AsS4 crystals. It is revealed that the piezo-optic coefficients are very high, ∼10-11 N/m2 in the order of magnitude. This implies that Tl3AsS4 can be referred to the best piezo-optic materials. The same concerns the elasto-optic coefficients, of which absolute values are in the interval 0.28-0.54. It is also found that, at the anisotropic and isotropic interactions with the slowest transverse and longitudinal acoustic waves, the acousto-optic figure of merit reaches extremely high values (1.99×10-12 s3/kg and 9.45×10-13 s3/kg, respectively). In other words, the Tl3AsS4 crystals can be referred to as one of the best acousto-optic materials for the visible and infrared spectral ranges.

Dilatometric, birefringent, electrooptic and gyrotropic properties of semiconductor-ferroelectric Sn2P2S6 have been experimentally studied and theoretically analysed. It has been shown that the spontaneous mechanical strains, optical birefringence increment and optical activity are governed by different critical exponents due to the temperature-dependent rotation of spontaneous polarisation vector permitted by the symmetry of low-temperature phase in Sn2P2S6 crystals. The critical exponent for the order parameter is estimated to be close to , thus corresponding to the vicinity of the tricritical point. Based on the results obtained for the temperature dependences of birefringence under different hydrostatic pressures, it has been demonstrated that the ferroelectric phase transition in Sn2P2S6 becomes of the first order under high pressures.

We present the results for thermal expansion coefficients of Sn2P2S6 crystals determined both in the crystallographic system and the system based on eigenvectors of thermal expansion tensor. Peculiarities of temperature evolution of the indicative surface of thermal expansion tensor for Sn2P2S6 are discussed, including the region of their ferroelectric phase transition.

In this paper the acoustic, elastic, piezooptic, photoelastic and acoustooptic properties of SrB 4 O 7 and PbB 4 O 7 crystals have been studied and thoroughly analyzed. The complete matrices of the corresponding coefficients have been obtained. The acoustooptic diffraction in PbB 4 O 7 crystals has been observed.

The results of studies for the refractive indices dispersion, optical activity, electro- and piezooptic effects, electrogyration effect, thermal expansion and ultrasonic wave velocities in organic-inorganic [(CH 2 OH) 3 CNH 3 )]H 2 PO 4 crystals are presented. The coefficients describing those effects are determined. It is found that [(CH 2 OH) 3 CNH 3 )]H 2 PO 4 crystals are characterized by a high electrooptic figure of merit.

The piezooptical (PO) parameters of the ferroelectric crystal Sn 2 P 2 S 6 with monoclinic symmetry are measured by an interferometric technique for the mechanical stress applied parallel to the three main crystallographic axes at light wavelength λ = 632.8 nm and room temperature (T = 293 K). Nine independent PO coefficients are determined experimentally. They exhibit quite large values: the largest measured component is π 11 = 15.6 pm N. The high PO coefficients presume potential applications of Sn 2 P 2 S 6 as high-efficient acousto-optic material.

We have developed an approach for analyzing the anisotropy of the acousto-optic figure of merit (AOFM) for lithium niobate crystals in the case of isotropic acousto-optic (AO) diffraction. The working relations for the effective elasto-optic coefficients and the AOFM have been derived. We have found that, under the conditions of isotropic AO diffraction, the maximum AOFM value for LiNbO3 is equal to 11.62×10(-15) s(3)/kg. This is peculiar for the geometry of AO interaction of the shear acoustic wave propagating in the Y-Z plane (the velocity 3994 m/s) with the optical wave polarized in the same plane. We have demonstrated that the maximum AOFM values are achieved mainly due to the essential anisotropy and high values of the elasto-optic coefficient of LiNbO3.

We have developed the approach for analyzing of anisotropy of acoustooptic figure of merit (AOFM) for lithium niobate crystals in the case of isotropic acoustooptic (AO) diffraction. The working relations for the effective elastooptic coefficients and the AOFM have been derived. We have found that, under the conditions of isotropic AO diffraction, the maximum AOFM value for LiNbO3 is equal tp 11.62x10-15s3/kg. It is peculiar for the geometry of AO interaction of the shear acoustic wave propagating in the YZ plane (the velocity 3994 m/s) with the optical wave polarized in the same plane. We have demonstrated that the maximum AOFM values are achieved mainly due to essential anisotropy and high values of the elastooptic coefficients of LiNbO3., 21 pages, 3 figures

We present comprehensive experimental measurements and analysis of anisotropy of the acoustic wave velocities for TI(3)AsS(4) crystals, including the obliquity and nonorthogonality of the acoustic waves, and the deviations from purely longitudinal and transverse polarization types. We have found that the crystals under analysis are characterized by rather low transverse wave velocities v(23) and v(32), which are both equal to 630 m/s. It is shown that the efficiency of acoustooptic (AO) interactions in TI(3)AsS(4) can be notably increased when providing anisotropic interaction with the slowest transverse acoustic wave. Under the previously mentioned conditions, the AO figure-of-merit can be estimated to be extremely high, i.e., approximately 3×10(-12) s(3)/kg.

The results of study of piezoelectrooptic (PEO) effect in the course of ferroelectric (Pb5Ge3O11) and ferroelectric-ferroelastic (Rochelle salt crystals) phase transitions are presented. It is shown that the temperature dependence of the combined PEO coefficients corresponds to the Curie-Weiss law. Basing on the studies for the combined PEO effects in LiNbO3 and LiTaO3 crystals, it is shown that the effect is interchangeable, i.e. its coefficients determined independently from the electrooptic and piezooptic experiments are the same. Large PEO effect is observed in LiNbO3 crystals, where electrooptic coefficient r22 increases almost two times after the action of mechanical stress σ 2 = 3.7× 10 5N/m2.

Photoelastic coefficients of beta-BaB2O4 and Li2B4O7 crystals are calculated on the basis of piezooptic measurements performed with interferometric technique and the elastic compliance and stiffness data. Using the experimental results, the acoustooptic (AO) figure of merit (FM) has been estimated for the possible geometries of AO interaction. It is shown that the AO FM for the ABO and LTB crystals reach respectively the values M2=243.4*10-15s3/kg and M2=2.57*10-15s3/kg, if the interaction with the slowest ultrasonic waves (v=933.5m/s and v=3173m/s) is concerned. The directions of propagation and polarization of those acoustic waves are obtained on the basis of construction of indicative surfaces of the acoustic wave velocities.

The optical (refractive indices, piezooptic coefficients, optical damage thresholds and the transmission spectra) and the elastic properties of the borate crystals (BaB2O4, Li2B4O7 and CsLiB6O10) are investigated. The results of measurements for the velocity of longitudinal and transverse ultrasonic waves of the borate crystals are presented. The components of the elastic matrix Cmn of these crystals are calculated on the basis of the ultrasonic velocity measurements. Using the determined values of the refractive, elastic and elastooptic tensor components, we have calculated the largest values of the acoustooptic figure of merit M2.

The results of study of piezoelectrooptic (PEO) effect in the course of ferroelectric-ferroelastic phase transition in Rochelle salt crystals are presented. The coefficient of the combined effect is obtained from measurements of the changes in the electrooptic coefficients under the action of mechanical stress and the changes in the piezooptic coefficients under the action of electric field (or spontaneous polarization). It is shown experimentally that the values of both coefficients are the same, as predicted by the theory. The temperature dependence of the coefficient of combined PEO effect is obtained. Its anomalous behaviour at the phase transition appears due to the dielectric permitivity anomaly. It is also demonstrated that the change in the piezooptic coefficients at the phase transition in Rochelle salt crystals may be satisfactorily explained as a result of linear and quadratic PEO effect induced by spontaneous polarization.

For the first time, to the best of our knowledge, we have experimentally determined all of the components of the piezo-optic tensor for monoclinic crystals. This has been implemented on a specific example of triglycine sulfate crystals. Based on the results obtained, the complete elasto-optic tensor has been calculated. Acousto-optic figures of merit (AOFMs) have been estimated for the case of acousto-optic interaction occurring in the principal planes of the optical indicatrix ellipsoid and for geometries in which the highest elasto-optic coefficients are involved as effective parameters. It has been found that the highest AOFM value is equal to 6.8×10−15 s3/kg for the case of isotropic acousto-optic interaction with quasi-longitudinal acoustic waves in the principal planes. This AOFM is higher than the corresponding values typical for canonic acousto-optic materials, which are transparent in the deep ultraviolet spectral range.

We suggest a new approach for analyzing spatial anisotropy of acoustooptic figure of merit (AOFM). The relations for the effective elastooptic coefficients and the AOFM are derived for all possible types of acoustooptic (AO) interactions in optically isotropic media, including non-solid-state and solid-state amorphous media, and crystals belonging to the cubic system. Our approach allows for finding the optimal geometries of AO interactions characterized by the highest AOFM for a given material. The analysis is carried out on the examples of cubic KBr and KAl(SO4)2x12H2O crystals which represent different subgroups of the cubic symmetry class., 10 pages, 15 figures

We have analyzed the anisotropy of acoustooptic figure of merit M2 for KH2PO4 crystals. Basing on our results, the highest M2...

We present the results concerned with acoustic and elastic properties of Sn(2)P(2)S(6) crystals. The complete matrices of elastic stiffness and compliance coefficients are determined in both the crystallographic coordinate system and the system associated with eigenvectors of the elastic stiffness tensor. The acoustic slowness surfaces are constructed and the propagation and polarization directions of the slowest acoustic waves promising for acousto-optic interactions are determined on this basis. The acoustic obliquity angle and the deviation of polarization of the acoustic waves from purely transverse or longitudinal states are quantitatively analysed.

Interaction of acoustic and light waves with accounting for elastooptic and elastogyration effects is theoretically described. Collinear acoustogyration diffraction in quartz and paratellurite crystals is experimentally investigated and thoroughly analyzed. Piezogyration effect is experimentally studied for TeO2 crystals. The acoustogyration efficiency and the acoustogyration figure of merit calculated for a number of crystals (GaAs, TeO2 and SiO2) are shown to be too small for experimental detection. On the other hand, we demonstrate that the light diffraction at periodical distribution of the imaginary part of dielectric permittivity related to the piezogyration effect should, in principle, be observed for the case of interaction of optical waves with enantiomorphous ferroelastic domain structure and in cholesteric liquid crystals.

Piezooptic coefficients of Sn2P2S6 crystals are experimentally determined for and with the aid of interferometric technique. The components of the elastic stiffness tensor for these crystals are calculated on the basis of studies for the acoustic wave velocities. It is shown that estimated acoustooptic figure of merit can achieve extremely high values for Sn2P2S6 crystals.