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1
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Regular Trends of Acousto-Optic Interaction in Terahertz Region of Electromagnetic Radiation

100%
Nikitin P., Voloshinov V., Gerasimov V., Knyazev B.
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EN
Basic problems of acousto-optic interaction in terahertz region of electromagnetic spectrum are considered. We obtained experimental results that are fitted by generalized theoretical model developed with the goals to describe the interaction in detail. Our analysis showed that crystalline germanium is one of the best materials to observe the acousto-optic interaction in the terahertz range. The carried out study proved that a germanium based acousto-optic device could be used for fast and reliable deflection of monochromatic radiation in the terahertz spectral region.
2
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Acousto-Optic Characteristics in Media with Strong Acoustic Anisotropy

100%
Voloshin A., Balakshy V.
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EN
Calculations of acousto-optic diffraction spectrum are fulfilled on the basis of modified Raman-Nath equations which take into consideration the acoustic energy walk-off. It is shown that, depending on acousto-optic interaction geometry, the walk-off can change essentially angular and frequency ranges of the interaction. Coefficients of broadening are put in practice as characteristics of the walk-off influence. The calculations are carried out for 5° crystal cut of a paratellurite crystal in wide ranges of ultrasound frequencies and Bragg angles.
3
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Photoelastic Phenomena in Stressed Laser Heterostructures

80%
Kulakova L., Averkiev N., Lutetskiy A.
Acta Physica Polonica A
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2015
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vol. 127
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issue 1
87-89
EN
The theoretical analysis of optical properties change in cubic crystals caused by simultaneous action of longitudinal and shear strains due to the photo-elastic interaction has been performed. The polarization characteristics change of a primary linear polarized light wave during propagation in the crystal has been studied. Results of the calculations were used to analyze photo-elastic phenomena in stressed heterostructures at the introduction of an alternating shear strain. The comparison of photo-elastic and acousto-electron phenomena in the laser heterostructures has been fulfilled. The results have been confirmed by the experiments in the InGaAs/GaAs structures at the action of shear strains excited by the ultrasonic waves.
4
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Sensing Sound Pressure in an Anechoic Chamber Using Backscattered Laser Light

80%
Piper B., Koukoulas T.
Acta Physica Polonica A
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2015
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vol. 127
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issue 1
128-131
EN
Current standards for the measurement of the SI derived unit of sound-in-air pressure, the pascal, are based upon microphone reciprocity calibration and are achieved indirectly through microphone sensitivity. These methods require microphones of specific geometry and performance characteristics, effectively artefacts, and are traceable through standards for electrical and dimensional units. Measurement of acousto-optic interactions can provide a direct approach to measuring sound pressure. One acousto-optic interaction is the periodic scattering of photons caused by particles moving in a sinusoidal manner due to propagating sound across interference fringes formed at the intersection of two coherent laser beams. The sequence of these scattered photons, which is collected using telescopic optics and generated by a single photon counting device, can be autocorrelated to yield the periodicity of the photon events. Through mathematical analysis of the autocorrelation function it has been shown that acoustic particle velocity is inversely proportional to the time of the first minimum. This has effectively been shown for measurements in acoustic standing wave tubes and has been developed into a method which can be applied in an anechoic chamber. This paper describes the design and implementation of such a system which allows for a comparison of sound pressure measurements using optical and microphone based techniques.
5
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Acousto-Optic Modulator Driven by Surface Acoustic Waves

80%
Kakio S.
Acta Physica Polonica A
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2015
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vol. 127
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issue 1
15-19
EN
In this paper, an introduction to the design, fabrication, evaluation, and application of acousto-optic modulators using the Bragg diffraction of an optical guided wave in a channel optical waveguide due to a surface acoustic wave is provided. First, the surface acoustic wave mode dependence in the acousto-optic Bragg diffraction was discussed by considering the surface acoustic wave power required for the maximum diffraction P_{{100}} calculated using coupled mode theory and the measured P_{{100}} in Ti-diffused planar optical waveguides fabricated on LiNbO_{{3}} substrates. Next, performances of several devices that the author and the coworkers developed are reviewed. These include a waveguide-type acousto-optic modulator using a tapered crossed-channel proton-exchanged optical waveguide on a 128°-rotated Y-cut LiNbO_{{3}} substrate for an optical wavelength of 1.55 μm, a monolithically integrated tandem acousto-optic modulator in which several waveguide-type acousto-optic modulators are connected in tandem on the same substrate, and a waveguide-type acousto-optic modulator in which laser lights of the three primary colors, red, green, and blue, can be modulated by the same modulator at the same driving frequency.
6
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Acousto-Optical Tunable Transmissive Grating Beam Splitter

80%
Dieulangard A., Kastelik J., Dupont S., Gazalet J.
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EN
We present a tunable transmissive grating beam splitter for multiple laser line separation based on acousto-optic interaction in tellurium dioxide. Acousto-optic devices are well known for light modulation, frequency shifting, filtration or deflection. Unlike the classical operating modes of acousto-optic devices, we consider the simultaneous diffraction of several optical wavelengths by a single ultrasonic frequency. The device is based on the Bragg anisotropic interaction in the specific "tangent phase matching" configuration. The acousto-optic interaction takes place with a single ultrasonic frequency and the diffraction efficiency remains high over a wide optical spectral range. The different diffracted beams are then angularly well separated, due to the slow velocity of the ultrasonic wave propagating in tellurium dioxide. The optical bandwidth is directly related to the operating ultrasonic frequency. Numerical calculations were carried out to determine the main parameters of the device: operating ultrasonic frequency, optical bandwidth, tunability range, crystalline cut and transducer length. A practical device has been designed for visible spectrum. Experimental results are presented as for example a spectral bandwidth from 450 nm to 550 nm with a carrier frequency f_0=125 MHz.
7
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Acousto-Optic Diffraction by Shear Horizontal Surface Acoustic Waves in 36° Rotated Y-Cut X-Propagation Lithium Tantalate

80%
Rimeika R., Čiplys D., Shur M.
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EN
We have investigated the acousto-optic diffraction by shear horizontal surface acoustic waves in 36° rotated Y-cut X-propagation lithium tantalate (LiTaO_{{3}}) crystals. The measurements were performed at the optical wavelength 633 nm of He-Ne laser and acoustic wavelengths of 50-60 μ m. The anisotropic diffraction with the light polarization rotation in the transmission mode was observed. The measured and calculated values of the light incidence angle corresponding to the strongest diffraction differed significantly. A narrow strip of a thin metal film deposited on the crystal surface drastically affected the light diffraction. We attribute these effects to the conversion processes between the shear horizontal leaky surface acoustic wave and shear horizontal surface skimming bulk wave.
8
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Acousto-Optic Tunable Filters for Imaging Applications in the 2-4~μm with Low RF Drive Power

80%
Valle S., Ward J., Pannell C., Johnson N.
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EN
The λ^{2} dependence on acoustic field intensity (and hence RF drive power) can render large aperture acousto-optic tunable filters impractical for many applications beyond about 2 μm. One potential technique for reducing the RF drive-power requirement is to configure an acousto-optic tunable filter such that the interaction region is at acoustic resonance. We describe an acousto-optic tunable filter that operates at resonance and present an analysis of the predicted performance. In addition, we address the practical issues in deploying such a scheme. Finally, we present results of a prototype "resonant acousto-optic tunable filter" operating in the 1-2 μm region.
9
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New Method to Calculate Spatial Distribution of Acousto-Optic Figure of Merit in Crystals

61%
Muromets A., Trushin A.
Acta Physica Polonica A
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2015
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vol. 127
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issue 1
93-95
EN
We propose a novel method to calculate acousto-optic figure of merit in crystals. Calculations are performed in laboratory coordinate system where Z'-axis is collinear with wave vector of ultrasound and the Fresnel equation is considered as an equation on the third component of refractive index vector. The method is applicable to both uniaxial and biaxial crystals. In this paper, we compared obtained values of acousto-optic figure of merit with values from literature data for uniaxial crystals such as paratellurite, lithium niobate, tellurium and for biaxial crystals such as lead and strontium tetraborates. Calculations in paratellurite were carried out for slow-shear acoustic wave propagating along [110] crystal axis. In lithium niobate crystal, we perform comparison with results for geometry of acousto-optic interaction where acoustic wave vector forms 88° angle with X crystal axis and 150.4° angle with Z crystal axis. In tellurium crystal, we investigate geometries applied in infrared deflectors. In SrB_4O_7 and PbB_4O_7 crystals we analyze acousto-optic characteristics of slow-shear mode propagating along [100] crystal axis. Spatial distributions of acousto-optic figure of merit and acoustic frequency for the mentioned acousto-optic interaction geometries are presented.
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