Acousto-optic Figure Of Merit Research Articles

Effect of CsCl nanocrystallization on the acousto-optic properties of GeS2-Sb2S3-CsCl chalcogenide glass-ceramics

Crystallization of chalcogenide glasses provides a new possibility to decoupling the trade-off between acousto-optic figure of merit (M2) and acoustic attenuation (α) properties of acousto-optic materials. In this work, 62.5GeS2-12.5Sb2S3-25CsCl chalcogenide glasses ceramics were prepared, and CsCl nanocrystals were precipitated and evidenced by using scanning electron microscopy and X-ray diffractometer. The precipitation of CsCl nanocrystals led to a 10 % decrease in M2 from 113.85 to 102.08 × 10−18 s3/g, but also to a substantial improvement in α, which decreased by 38 % from 3.28 to 2.03 dB/cm. The glass crystallization that together with a rearrangement of the glass network structure would result in the enhancement of network rigidity of the residual glass matrix, thus contributing to the reduction of acoustic attenuation.

Increase in the acousto-optic figure of merit in SiO2 crystals due to optical activity. Anisotropic acousto-optic interactions

Increase in the acousto-optic figure of merit in SiO2 crystals due to optical activity. Anisotropic acousto-optic interactions

Investigation of the Ga-Sb-S chalcogenide glass with low thermo-optic coefficient as an acousto-optic material

In this study, two series of GaxSb40-xS60 (x = 4, 6, 8, 10 mol%) and GaySb36S64-y (y = 3, 5, 6 mol%) glasses were prepared and the relationship between their compositional and acousto-optic (AO) properties was investigated systematically for the first time. In the GaySb36S64-y system, the AO figure of merit (M2) increased as the Ga increased, and the maximum M2 of the Ga6Sb36S58 glass was 455.78 × 10−18 s3/g, which is ∼301 times greater than that of fused silica and ∼2.5 times greater than that of As2S3 chalcogenide (ChG) glass at 1550 nm. However, its thermo-optic coefficients (dn/dT) varied greatly (32.1 × 10−6 °C−1–57.2 × 10−6 °C−1), and acoustic attenuations (α) at 10 MHz were high, from 5.446 dB/cm to 7.274 dB/cm. In the GaxSb40-xS60 glass system, the M2 value and α at different ultrasonic frequencies gradually decreased with the improvement of Ga. Compared with the GaySb36S64-y system, the GaxSb40-xS60 glass system had lower α (at 10 MHz) and dn/dT, which are 5.001 dB/cm–5.563 dB/cm and 17.3 × 10−6 °C−1–55.6 × 10−6 °C−1, respectively. These results provide a significant reference for the further development of novel ChG glasses and help expand their application fields.

Acoustic and acousto-optic properties of Ge-=SUB=-a-=/SUB=-Se-=SUB=-b-=/SUB=-Te-=SUB=-c-=/SUB=- and Si-=SUB=-a-=/SUB=-Se-=SUB=-b-=/SUB=-Te-=SUB=-c-=/SUB=- glasses in case diffraction on longitudinal and shear acoustic waves

We investigated acoustic and acousto-optic properties of glasses based on germanium, selenium, silicon and tellurium. The results of measurement are presented for two group of glasses including germanium, selenium and tellurium (GeSeTe) and silicon and tellurium (SiTe). The major characteristics of glasses such as the velocity of longitudinal and shear acoustic waves as well as the values of figure of merit are presented. The values of figure of merit are obtained by diffraction on longitudinal and shear acoustic waves at the wavelength of optical radiation λ = 3.39 μm. We also present the results of measurements of acoustic attenuation values α for longitudinal and shear acoustic waves in tellurium glasses at ultrasound frequencies in the range f = 75-100 MHz. Keywords: acousto-optics, acousto-optic figure of merit, germanium, selenium, silicon, tellurium, attenuation acoustic waves.

FEM Analysis of Various Multilayer Structures for CMOS Compatible Wearable Acousto-Optic Devices.

Lately, wearable applications featuring photonic on-chip sensors are on the rise. Among many ways of controlling and/or modulating, the acousto-optic technique is seen to be a popular technique. This paper undertakes the study of different multilayer structures that can be fabricated for realizing an acousto-optic device, the objective being to obtain a high acousto-optic figure of merit (AOFM). By varying the thicknesses of the layers of these materials, several properties are discussed. The study shows that the multilayer thin film structure-based devices can give a high value of electromechanical coupling coefficient (k2) and a high AOFM as compared to the bulk piezoelectric/optical materials. The study is conducted to find the optimal normalised thickness of the multilayer structures with a material possessing the best optical and piezoelectric properties for fabricating acousto-optic devices. Based on simulations and studies of SAW propagation characteristics such as the electromechanical coupling coefficient (k2) and phase velocity (v), the acousto-optic figure of merit is calculated. The maximum value of the acousto-optic figure of merit achieved is higher than the AOFM of all the individual materials used in these layer structures. The suggested SAW device has potential application in wearable and small footprint acousto-optic devices and gives better results than those made with bulk piezoelectric materials.

Novel acousto-optic material based on Ge-Te-AgI chalcohalide glasses

A series of (GeTe4.3)100−x(AgI)x (x = 5, 10, 15, 20, 25, 30 mol%) chalcohalide glasses was prepared to investigate their potential in acousto-optic (AO) materials. Detailed thermal and optical properties of these glasses have been analyzed by DSC, XRD and FTIR. Meanwhile, refractive index, density, elastic modulus, acoustic velocity and attenuation, and the AO figure of merit (M2) were also reported. The results indicated that all these glasses presented a single glass transition temperature (Tg) and a single crystallization peak (Tx), and Tg decreases while Tx increases with the addition of AgI. X-ray power diffraction investigation showed the amorphous state of these synthesized glasses. They all have a wide transparent window from 2 to 20 μm, and acoustic attenuation was observed almost linearly proportional to the frequency at room temperature. Furthermore, refractive index and density increase, while acoustic velocity and elastic modulus decreases monotonously upon introducing AgI to GeTe4.3. The maximum refractive index (n = 3.729) and minimum acoustic velocity (V = 2.037 × 103 m/s) appeared in 70GeTe4.3–30AgI glass, thereby resulting in a maximum M2 of 3671 × 10−15 s3/kg at 10.6 μm. The outstandingly high M2 of this vitreous material make it attractive for far-infrared (FIR) AO modulators that require greater diffraction efficiency.

Anisotropy of acousto-optic figure of merit in the XZ plane of Pb5Ge3O11 crystals

Anisotropy of acousto-optic figure of merit in the XZ plane of Pb₅Ge₃O₁₁ crystals

Anisotropy of acoustic and thermal expansion properties of TlInSe2 crystals

ABSTRACTBased 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 axes parallel to the principal crystallographic directions. The lowest velocities of acoustic eigenwaves are used to estimate the acousto-optic figure of merit. We analyse deviations from purely longitudinal and transverse polarization states, as well as the obliquity of acoustic energy flow. Temperature dependences of strains along the three principal crystallographic directions and of acoustic wave velocities v11, v22 and v33 are measured. Anomalous behaviour of these parameters occur at T1245 K and T2145 K. It is shown that the symmetry of TlInSe2 becomes lower than tetragonal below the temperature point T1.

Pulse Modulation of Multicolor Radiation Via Light Diffraction by Sound

Three acousto-optic materials, ТеО2, SiO2, and LiNbO3, widely used in production of acousto-optic cells for pulse modulation of the multicolor optical radiation, have been compared. It is demonstrated that the ТеО2 acousto-optic cell has an undoubted advantage in terms of the electric power consumption, first of all, due to its high acousto-optic figure of merit, while SiO2 and LiNbO3 cells are preferable from the viewpoint of the lowest distortions in transformation of electrical pulses into optical signals. Main theoretical conclusions have been confirmed by experiments on modulation of the multicolor Ar laser radiation.

Anisotropy of acousto–optic figure of merit in lithium tetraborate crystals

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 × 10−15 s3/kg, is peculiar for the isotropic acousto–optic interaction of the incident ordinary optical wave with the quasi-longitudinal acoustic wave. For the case of anisotropic diffraction in Li2B4O7, the maximum 1.87 × 10−15 s3/kg can be reached using the interaction of the extraordinary optical wave with the quasi-longitudinal acoustic wave. The case of collinear diffraction is characterized by small AOFMs, with the largest value 0.26 × 10−15 s3/kg.

Piezo-optic and elasto-optic properties of monoclinic triglycine sulfate crystals.

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.

Anisotropy of acousto-optic figure of merit for LiNbO3 crystals: anisotropic diffraction.

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 LiNbO3 crystals. The relations for the effective elasto-optic coefficients and the AOFM are obtained for the three types of acousto-optic (AO) interactions peculiar for the anisotropic AO diffraction: the interaction of a so-called type VII with a quasi-longitudinal acoustic wave and the interactions of types VIII and IX with two quasi-transverse acoustic waves. The AO diffraction geometries providing maximal AOFM values have been determined for each of the mentioned interaction types. We have found that the maximum AOFM proper for LiNbO3 is equal to 15.9×10-15 s3/kg. This value is achieved at the type IX of AO interactions in the interaction plane rotated by 60.0deg around the principal X axis with respect to the principal X-Z plane. The type VIII of AO interactions is characterized by a comparable AOFM (15.1×10-15 s3/kg), which is realized in the Y-Z interaction plane. A close comparison of our results with the available experimental data demonstrates their fairly good agreement.

Conditions for obtaining backward collinear isotropic acousto-optic interaction in germanium and iodic acid crystals

The possibility of experimentally obtaining backward collinear isotropic acousto-optic interaction based on bulk ultrasonic waves and terahertz electromagnetic waves is considered. The magnitudes of the acousto-optic figure of merit and the corresponding acoustic frequencies are calculated for the basic crystallographic axes in germanium and iodic acid crystals. The acousto-optic parameters of both crystals are compared.

Spiral patterns in the anisotropy of acousto-optic figure of merit for LiNbO3 crystals: The case of anisotropic diffraction in the interaction plane XY

We have analyzed the anisotropy of acousto-optic figure of merit (AOFM) in LiNbO3 crystals for the three different types of...

Anisotropy of the acousto-optic figure of merit for LiNbO₃ crystals: isotropic diffraction.

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.

Influence of driving power on the performance of UV KDP-based acousto-optical tunable filters

Spectral imaging is a powerful tool for remote sensing applications. Among other valuable options, acousto-optical tunable filters (AOTF) offer interesting properties to this class of instruments. When sensitivity to ultra-violet (UV) light is required, KH2PO4 crystal (KDP) is a good choice for the acousto-optic (AO) interaction medium as its AO figure of merit is relatively large compared to other materials transparent in UV. However, it generally requires more acoustic power than well-known TeO2-based devices to achieve the highest diffraction efficiency. We report on measurements performed with a KDP-based AOTF (9-cut) driven with RF signals up to 3 W. It has been found that owing to various effects (Joules, acoustic wave attenuation,…) the heating of the crystal by a few degrees yields severe alteration of the AOTF spectral transmission function (STF): shift of the central wavelength, increase of the bandwidth and decrease of the peak filter efficiency have been observed. These three effects degrade the AOTF overall performance if not taken into account. This paper presents the experimental evidences and shows how a temperature-dependent AOTF model allows to derive the inner temperature of the device. Possible reasons for the flattening of the STF are also discussed.

Imaging AOTFs with Low RF Power in Deep-UV and Mid-IR

Acousto-Optic Tunable Filters (AOTFs) are commonly used for applications where high speed tuning and narrow spectral resolu- tion are required. The RF drive power for peak diffraction efficiency increases as λ2 and depends on the acousto-optic figure of merit (M2), which is material dependent. In the VIS-IR region between 450nm and 4.5μm tellurium dioxide (TeO2) is the common material of choice due to the high M2. At longer wavelengths (up to about 12μm) the mercurous halides and single crystal tellurium show promise. In both cases the λ2 dependency dominates the RF power consumption and for wavelengths beyond 3.5μm the RF power consumption is above the practical limit (>5W) for larger aperture AOTF(> 10mm × 10mm). In the UV range (200nm – 400nm) the λ2 dependency is no longer dominant and the power consumption depends mainly on the M2,however, for most materials transparent in the UV the M2 is poor and thus the drive power will again be excessive (>5W). In order to reduce the RF power requirement to reach peak diffraction efficiency, a resonant configuration in crystal quartz shows promise, especially in the UV range due to its low acoustic attenuation. We describe an AOTF operating in resonance made of crystal quartz, where the reduction of RF power consumption will be reduced by a factor between 15 and 20 compared to a conventional AOTF, thus reducing the power consumption to be within the practical limit (<5W).

Anomalous behaviour of acoustooptic figure of merit under the conditions of collinear diffraction

Anisotropies of the acoustooptic figure of merit (AOFM) and the effective elastooptic coefficient under the conditions of collinear diffraction have...

Photoelastic and Acousto-optic Properties of KDP Crystal Applied in Wide Angle Tunable Filters

The paper presents results on calculation and measurement of acousto-optic properties of KDP crystals applied in imaging tunable acousto-optic filters operating in the ultraviolet region of electromagnetic light. Effective photoelastic coefficients and acousto-optic figures of merit are evaluated in the mode of wide angle diffraction. The carried out analysis is based on results of measurements of the efficiency of Bragg diffraction at the same frequency of ultrasound but at two different angles of light incidence in the KDP crystal. We used the crystal in an imaging acousto-optic tunable filter operating at the wavelengths of light 405, 532 and 633nm. The filters apply a slow shear acoustic wave propagating at the angles α=90 and α=120 relatively to the [100] axis in (010) plane of the crystal. Differences between the measured data on the photoelastic coefficients and those found in literature are discussed in the presentation.

Optimum Configuration for Acousto-optical Modulator Made of KGW

Acousto-optical figure-of merit has been investigated for KGd(WO4)2 crystal, which is applicable to control high intensity laser radiation. Using the data on acoustic velocities obtained earlier and the experimentally determined coefficients of light diffraction on acoustic waves, we have calculated for the first time 12 elements of the upper half of the elasto-optic matrix. This new data permitted to calculate angular dependence of acousto-optical figure-of-merit with respect to the light polarization for “isotropic” diffraction and to find the optimum geometry, which ensures maximum diffraction efficiency.