Piezo-optic Coefficients Research Articles

Piezo-optical properties and infrared spectra of Rb2SO4 crystals

The paper deals with the dispersion dependences of birefringence Δni(λ) of the mechanically free and uniaxially clamped Rb2SO4 crystal along different crystal-physical axes at room temperature. It was found that the crystal has an insignificant normal dispersion d(Δnx)/dλ χ ≤ 0, and uniaxial compressions σm do not change the character, but only the slope of the dependences Δni(λ). Uniaxial loads shift the position of the optical isotropic point both in the short-wavelength (σz) and in the long-wavelength part of the spectrum (σy). The spectral dependences of the combined piezo-optical coefficients πkmo(λ) were calculated and it was found that they have an insignificant dispersion dependence, and the absolute values of the piezo-optical coefficients π31o and π21o are equal to each other in the vicinity of the optical isotropic point at the light wavelength λ = 490 nm. The reflection spectra of Rb2SO4 crystals were measured in the infrared range at room temperature using FT-IR spectrometer and synchrotron radiation and the corresponding ab initio calculations of the phonon partial density of states and the dielectric function were performed.

Optoacoustic detection of nanosecond time scale photoinduced lensing effects in liquids

An all-optical photoinduced lensing method is used to excite and monitor acoustic waves in liquids. Following optical absorption, the laser pulse induces a localized temperature gradient that launches pressure waves in the excited region at the nanosecond time scale. This generates a lens-like optical element in the sample. A probe laser beam senses the refractive index change due to the acoustic and thermal effects. Piezo-optic and thermo-optic coefficients govern how the refractive index of a material changes in response to mechanical stress and temperature variations, respectively. These effects are connected to the physical properties of the liquids and can be accessed by theoretically describing the intensity signal. A complete set of physical properties of ten liquids are quantitatively described in this work. These effects find applications in a wide range of fields, from optical communication, ultrasonic imaging, and sensing to adaptive optics and fundamental research.

Photoelasticity of CNGS crystals.

All piezo-optic coefficients (POCs) and elasto-optic coefficients (ELOCs) of C a 3 N b G a 3 S i 2 O 14 (CNGS) and C a 3 T a G a 3 S i 2 O 14 (CTGS) trigonal crystals of the langasite group are determined from quantum mechanical calculations based on the hybrid density functional theory, as implemented in the CRYSTAL program. The calculation results for CTGS crystals are compared with experimental data. Indicative surfaces of piezo- and elasto-optic effects are constructed based on the POC and ELOC matrices of CNGS crystals and the largest values of these effects are determined. The maximum values of the coefficient of the acousto-optic figure of merit M 2 of the CNGS crystal are determined for the geometries of elasto-optic interaction, which correspond to the maxima of the elasto-optic effect. These results are compared to the corresponding results for CTGS and langasite crystals. The spectral dependence of the POCs and ELOCs of CNGS and CTGS crystals on the light wavelength is investigated in the 600-1500nm range.

On the low-temperature isotropic point in Rb2SO4 crystals

In this work, Rb2SO4 single crystals of good optical quality were synthesized and the spectral (300–700 nm) and temperature (300–77 K) dependencies of birefringence were experimentally investigated. It was found that with a temperature decreasing, at a temperature of T = 85 K and a light wavelength of λ = 500 nm, the birefringence value in the Y direction is zero (Δny = nz – nх = 0), which testifies to the existence of a new isotropic point. The influence of uniaxial compression on changes in Δny (Т, λ) was studied, and their significant sensitivity was revealed. The temperature-baric and spectral-baric changes of the isotropic point position were analyzed, based on which the temperature-spectral-baric diagram of the isotropic state of the crystal was constructed, which will be of practical importance for the use of crystal as an active element in a crystal-optical temperature sensor for a low-temperature region. Based on the Δny (Т, λ, σ) dependencies, the combined piezo-optic coefficients of the crystal were estimated, and it was assumed that not only thermal but also mechanical deformation of the optical indicatrix takes place in the vicinity of the isotropic point.

Optical detection of the ultrasound-induced pulsed thermal lens close to the ice-water phase transition.

Piezo-optic and thermo-optic coefficients are important material properties that play a critical role in the design and optimization of many optical devices. The ability to accurately measure and control these coefficients is essential for achieving high performance and reliability in a wide range of applications. In this article, we use the optical detection of the ultrasound-induced thermal lens effect to investigate these properties for water at low temperatures. The results show that the anomalous behavior of water around 4°C is easily observed. The thermal lens method is used to determine the temperature dependence of the piezo-optic and thermo-optic coefficients.

CRYSTAL OPTICAL PARAMETERS OF UNIAXIALLY COMPRESSED LiNaSO4 CRYSTALS

In the work, a LiNaSO 4 crystal was synthesized and spectral study of its birefringence Δ n i was carried out. It was found that the cation substitution of potassium with sodium(LiKSO 4 → LiNaSO 4 ) in the LiBSO 4 systemsignificantly increases the refractive index and birefringence (by more than an order of magnitude) compared to the substitutions K + → Rb + and K + → (NH 4 ) + . It is shown that the high optical anisotropy of the lithium sodium sulfate crystal can be related to the asymmetry of the second coordination environment of anions in its structure. First-principles calculations of the electronic and optical properties of LiNaSO 4 crystals were performed. From the calculated spectra of the real and imaginary parts of the dielectric function, the spectral dependence of the refractive indices and the extinction coefficients were obtained. The calculated dispersions of the refractive indices of the LiNaSO 4 crystalfor the visible part of the spectrum satisfy the ratio n z > n x,y . The order of the obtained curves coincides with those determined experimentally. The theoretically obtained values of refractive indices are lower (within 8%) than the experimental ones. Such a deviation can be caused by the negative contribution of infrared absorption in the crystal, which is not taken into account in the CASTEP code. It is worth noting, however, that a very good reproduction of the dispersion changes of the refractive indices was obtained from the calculations. Here, the values of d (Δ n i )/ dλ for n x,y (λ) and n z (λ) dependences are practically the same with the maximum deviation of 3.3·10 –5 nm –1 from those determined experimentally. The behavior of optical birefringence of LiNaSO 4 crystals was studied under conditions of uniaxial pressures applied along the main crystal physical directions. The uniaxial pressure applied along mutually perpendicular directions was found to lead to changes in birefringence, different in magnitude and sign. Dispersion effect of birefringence weakens under the influence of stress σ ⊥ z and strengthens in the opposite case of σ || z. Keywords : crystal, birefringence, uniaxial pressure, piezo-optical coefficients, refractive index.

Photoelastic Properties of Trigonal Crystals

All possible experimental geometries of the piezo-optic effect in crystals of trigonal symmetry are studied in detail through the interferometric technique, and the corresponding expressions for the calculation of piezo-optic coefficients (POCs) πim and some sums of πim based on experimental data obtained from the samples of direct and X/45°-cuts are given. The reliability of the values of POCs is proven by the convergence of πim obtained from different experimental geometries as well as by the convergence of some sums of POCs. Because both the signs and the absolute values of POCs π14 and π41 are defined by the choice of the right crystal-physics coordinate system, we here use the system whereby the condition S14 > 0 is fulfilled (S14 is an elastic compliance coefficient). The absolute value and the sign of S14 are determined by piezo-optic interferometric method from two experimental geometries. The errors of POCs are calculated as mean square values of the errors of the half-wave stresses and the elastic term. All components of the matrix of elasto-optic coefficients pin are calculated based on POCs and elastic stiffness coefficients. The technique is tested on LiTaO3 crystal. The obtained results are compared with the corresponding data for trigonal LiNbO3 and Ca3TaGa3Si2O14 crystals.

Anisotropy of piezo-optic and elasto-optic effects in langasite family crystals

The surfaces of the photoelasticity effects spatial distribution are constructed for langasite (LGS) and catangasite (CTGS) crystals basing on the matrices of piezo-optic and elastic-optic coefficients (POC and ELOC). It is shown that the maxima of the longitudinal piezo-optic effect (POE) are commensurate for both crystals and correspond to POC π33; the maximum value of transverse POE (vectors of uniaxial pressure and light wave polarization are mutually perpendicular) in CTGS crystals is almost two times higher comparing to LGS. The maxima of the transverse elastic-optic effect (ELOE) are also significantly higher in CTGS. It should be emphasized that the maxima of the surfaces of the transverse POE are not located on crystallographic axes, but correspond to the directions that are shifted for 13 … 33° from optical axis of the crystals. Thus, the angle between maximum ELOE and optical axis in CTGS equals 13°. The maximum values of POE, ELOE and the directions of the maxima were determined analytically using the method of partial derivatives. The acousto-optic figure of merit M2 was determined for the ELOE maxima. It has been shown that this value is two times higher for CTGS, comparing with LGS. The first attempt to make the correlation between the POE, ELOE maxima and structural properties of these crystals has been carries out.

Induction and detection of pressure waves by pulsed thermal lens technique in water-ethanol mixtures.

The mode-mismatched dual-beam thermal lens technique is widely applied in the characterization of optical and thermo-physical properties of solids and liquids. The technique has also been used to investigate transient acoustic waves induced by pulsed laser excitation at the nanosecond time scale. In this paper, we developed a semi-analytical model to describe the transient acoustic wave that allows a fitting procedure to get the physical properties of fluid samples. The method was used to investigate samples with different mixtures of ethanol and water, and quantitative information of piezo-optic coefficient and sound speed are evaluated for the fluid mixtures.

Thermal lens in diode-pumped square-section rods of Nd-doped phosphate glass and 0.5%Nd:5%Lu:CaF2 crystal: simulations and experiments.

We performed simulations and experiments of wavefront distortions induced by propagating through diode-pumped square-section amplifying laser rods of Nd-doped phosphate glass and 0.5%Nd:5%Lu:CaF2. We observed that depending on the material, wavefront distortions' profile can vary from a circular lens-like distortion to a complex astigmatic distortion. We showed that this difference comes from the relative sign of piezo-optic tensor coefficients.

Full set of piezo-optic and elasto-optic coefficients of Ca3TaGa3Si2O14 crystals at room temperature.

The photoelasticity of the Ca3TaGa3Si2O14 (CTGS) crystal was studied by an interferometric method based on a single-pass Mach-Zehnder interferometer. The maximum number of sample orientations for the piezo-optic experiments was applied to prove accuracy in the determination of the piezo-optic coefficients. Based on the matrices of the piezo-optic coefficients and the elastic stiffness coefficients, all the coefficients pik of the elastic-optic matrix are calculated. For the highest pik coefficient, the acousto-optic efficiency is evaluated. The results obtained for CTGS are compared with the corresponding results for La3Ga5SiO14 (langasite) crystals. The highest acousto-optic figure of merit of CTGS M2=1.66⋅10-15s3/kg is two and three times higher, compared with langasite and strontium borate, respectively, which are often used for acousto-optic modulation of light in the ultraviolet spectral range.

Experimental determination of full matrices of the piezo-optic and elasto-optic coefficients for Pb5Ge3O11 crystals.

We determine full matrices of piezo-optic and elasto-optic coefficients for lead germanate crystals, Pb5Ge3O11, 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 Pb5Ge3O11 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 37×10-15s3/kg), 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.

Comparative Study of the Photoelastic Anisotropy of Si and GaAs

In this paper we present the results of experiments on single-crystalline (100)Si and (100)GaAs wafers which allow us to determine the degree of photoelastic anisotropy Ape in the near-infrared range (probing laser wavelength λ ≈ 1.3 μm). Ape is introduced as the absolute value of (π11 − π12 − π44)/(π11 − π12 + π44). π11, π12 and π44 are the piezo-optical coefficients. The experiments were carried out using a scanning infrared depolarization imager (SIRD) measurement system equipped with special calibration setups. These setups produce a defined diametrical loading of the wafer. The different measurement and analysis strategies are explicated. The generated birefringence and shear stress equivalent maps impressively illustrate the respective opposite photoelastic properties of Si and GaAs. The experimental results are compared with simulation data on the basis of a classic 2D stress model, taking into account the crystallographic anisotropy by applying the full tensor calculus. For GaAs, Ape is determined to be 0.41 ± 0.02. This value and the best-matching coefficients πij which were used for simulation are compared with data available from publications of the past few decades.

Nanosecond pressure transient detection of laser-induced thermal lens

We use the thermal lens technique in the nanosecond time scale to describe the acoustic wave effect in liquids and the corresponding correlation with the speed of sound in the fluid, volumetric thermal expansion, and piezo-optic coefficient. These physical properties are found to be directly correlated to the anomalous effects observed in the transients at the nanosecond time scale, where acoustic waves dominate the thermal lens signal inducing an oscillating transient. Our results suggest the application of the thermal lens to study the generation and the detection of thermo-acoustic waves in liquids, which makes this method interesting for all-optoacoustic ultrasound detection and imaging.

Measurement of the piezooptic coefficient of ceramic YAG and analysis of depolarization

To analyze the thermal birefringence effects in laser gain materials, knowledge of the piezooptic coefficients of the materials is required. The piezooptic coefficients of ceramic YAG were measured using the four-point bending method. To our knowledge, this is the first report of this measurement for ceramic YAG. With the measured values, the depolarization of a ceramic YAG laser was analyzed. Overall, the results agree with that of single-crystal YAG in the [111] direction. Ceramic YAG will produce a larger depolarization compared with [100]-direction YAG with an appropriate input polarization angle.

Specific features of refractive, piezo-optic and nonlinear optical dispersions of β-LiNH4SO4 single crystals

The crystals of LiNH4SO4 in β-modification are synthesized and the parameters of their crystalline unit cell are refined from XRPD spectra using Rietveld method. A refractive indices dispersions for mechanically free and uniaxially compressed crystals with pressures σm = 0–150 bar (m = X, Y and Z) along three principal crystallographic directions have been explored within 300–800 nm spectral range by spectral method. The influence of uniaxial mechanical pressure on the refractive parameters of the crystal has been established. The combined piezo-optic coefficients of the β-LiNH4SO4 versus wavelengths are found. The nonlinear optical phenomenon of the second harmonic generation (SHG) efficiencies is investigated for powdered samples using the modified Kurtz method at 1064 nm wavelength. The principal analysis of the dispersion allows to establish a new relation between the linear and nonlinear optical responses. Possible application of such crystals is discussed.

Photoelastic Properties of Potassium Sulfate Crystals

The spectral dependences of the absolute piezooptic coefficients of potassium sulfate crystals are studied. It is established that their dispersion dependence is insignificant. The matrix of elastooptic coefficients pin of these crystals is filled using the elastic stiffness coefficients and the absolute piezooptic coefficients. The coefficient of acoustooptical efficiency M2 is calculated. It is shown that, considering the maximum values, it is more than an order of magnitude higher than that of quartz and strontium borate crystals. Potassium sulfate crystals are proposed for use for acoustooptic modulation of ultraviolet radiation, taking into account the short-wavelength limit of their transparent region (~170 nm).

Photoelasticity of ammonium sulfate crystals

All the components of πim matrix of the piezo-optic coefficients of ammonium sulfate crystals are defined using the interferometric method based on the one-pass Mach-Zehnder interferometer. All components of the рin matrix of elasto-optic coefficients are calculated on the basis of the πim matrix and elastic stiffness coefficients Сmn. Ammonium sulfate crystal should be attributed to the best photoelastic crystalline materials considering the highest values of πim and рin coefficients. The highest values of the acousto-optic figure of merit M2 are also established. The value of M2 of this crystal is 1–2 orders of magnitude higher than the value of M2 of known materials suitable for acousto-optic modulation of light in the ultraviolet spectrum region.

Laser-stimulated piezo-optical and third harmonic generation studies for Na2O–Sb2O3 glass ceramics-influence of gold ions

Sodium antimonate glass ceramics with different concentrations of Au2O3 were synthesized. The prepared samples were characterized by XRD, XPS, SEM and TEM techniques. These studies have revealed that the samples consist of multiple crystalline phases composed of Sb3+, Sb5+, Au3+ ions, and Au0 particles; moreover these studies have indicated growing proportion of Au0 particles and Sb5+crystal phases (Na2Sb2O6) with increase of Au2O3 concentration. IR and Raman spectral studies have pointed out an increasing degree of polymerization of the glass network with increase of Au2O3 content while optical absorption studies indicated surface plasmon resonance effects. Nd: YAG laser (λ = 1320 nm and pulse width 8 ns) was used for inducing third harmonic generation (THG) signal. Later, THG signal intensity of Nd: YAG laser (λ = 1064 nm and pulse width of 20 ns) vs fundamental beam power density was recorded. The results indicated the maximum intensity for the samples containing a low concentration of Au2O3. For inducing piezo-optical effects, Nd: YAG laser (λ = 1064 nm) and its doubled frequency beam λ = 532 nm (with simultaneous mechanical pressure) were used. The cw He-Ne laser of 20 mW (with beam diameter about 0.5 mm) was used as probing beam for measuring the piezo-optical effects in the photo-polarized samples. The variation of the intensity of the THG beam and piezo-optical coefficients were found to be the maximal for the samples mixed with small quantities of Au2O3. The detailed analysis of XRD, SEM, EPR, IR, optical absorption spectral results suggested that concentrations of Na3SbO3 and also Au2O3 crystal phases are maximal in these samples and are responsible for the maximal photoinduced effects, while the increasing presence of Na2Sb2O6 crystal phases and Au0 metallic particles are found to be hindrance for generation of third harmonic beams and also piezo-optical effects. Overall, the obtained results of nonlinear optical (NLO) and piezo-optical studies indicated that Na2O-Sb2O3 glass ceramics containing small traces of Au2O3 are useful for considering them for nonlinear optical triggering devices and piezo-electric devices.

Фотоупругие свойства кристаллов сульфата калия

The spectral dependences of the absolute piezo-optic coefficients of potassium sulfate crystals are studied and their insignificant dispersion dependence is established. The matrix of elasto-optic coefficients рin of these crystals is filled using the values of elastic stiffness coefficients and absolute piezo-optic coefficients. The coefficient of the acousto-optic efficiency М2 is estimated and it is shown that, considering the highest values, it is more than an order of magnitude higher than that of quartz and strontium borate crystals. Taking into account the short-wavelength boundary of the transparency region of potassium sulfate crystals (~ 170 nm), it is proposed to use them for acousto-optic modulation of ultraviolet radiation.