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1.
In the present research, we proposed a method of controlling the photoelastic constant using surface acoustic waves, which had not previously been reported, and carried out experimental studies thereof. A Bragg diffraction was carried out to determine the photoelastic constants of Ta2O5. As a result, it is confirmed that the photoelastic constant of a Ta2O5 thin film undergoing a sputtering process, during which surface acoustic waves were excited on the substrate, was about 2.19-2.27 times larger than those of thin films on which surface acoustic waves were not excited. 相似文献
2.
A. R. Muratov 《Journal of Experimental and Theoretical Physics》1997,85(5):887-897
A theory of parametric excitation of acoustic waves is constructed. It is shown that nonlinear attenuation is the main restriction
mechanism for a parametrically generated sound wave. The intensity of generated waves is directly proportional to the difference
ε between the value of pumping and bare attenuation. The calculated proportionality coefficient depends on the shape of the
generated sound wave. Why an ordinary pattern does not form for acoustic waves is explained. The structure of the spectrum
of excited waves was studied. It is shown that this structure has exponential asymptotic behavior at the frequency. The width
of the intensity distribution depends on the shape of a wave. For different cases it behaves as ε
α with α=1, 8/7, and 4/3. The results are compared with the experimental data of Ref. 5.
Zh. éksp. Teor. Fiz. 112, 1630–1648 (November 1997)
Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor. 相似文献
3.
S. N. Antonov 《Technical Physics》2016,61(1):130-133
An original acousto-optic modulator of depolarized laser radiation is based on a paratellurite crystal in the regime of anisotropic diffraction by a slow acoustic wave. Two acoustic waves with different frequencies are simultaneously excited in a single acousto-optic cell. Two diffraction orders of orthogonal polarizations at the exit from the cell are diffracted in opposite sides relative to the zero order. A polarization prism that is placed immediately behind the cell transforms the diffraction orders into a single output depolarized beam. The total efficiency is 96%. 相似文献
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6.
V. S. Sokolkin 《Acoustical Physics》2006,52(2):211-217
Scattering amplitudes and intensities of partial azimuthal harmonics and the total intensity of the scattered field are calculated for the case of transmission of longitudinal acoustic waves through a liquid rotating with acceleration. It is shown that the intensity of transmitted waves depends on the angular acceleration and does not depend on the angular velocity of the vortex rotation. 相似文献
7.
The problem of anisotropic Bragg diffraction of nonpolarized light by a slow acoustic wave in a TeO2 crystal is solved. Two independent acoustic waves are excited in the crystal. Nonpolarized light splits in the crystal into
two orthogonally polarized eigenmodes, either diffracting by its associated acoustic beam. Conditions under which the angles
of incidence and diffraction are the same for both diffraction processes are found. Depending on the acoustic frequency, the
diffracted light at the exit from the crystal may be represented either by a single nonpolarized beam or by two orthogonally
polarized beams with different directions and orthogonal polarizations. This may provide a high diffraction efficiency (up
to 100%) for nonpolarized light in a TeO2 crystal. Theoretical calculations are supported by experiments. Modulators capable of controlling a high-power laser operating
at a wavelength of 1.06 μm are fabricated. 相似文献
8.
V. V. Orlov 《Optics and Spectroscopy》2002,92(5):795-799
The wave field arising in the volume of superposed holograms is obtained with allowance for multiple wave diffraction on holographic cross-modulation gratings. It is shown that cross-talk interference waves are generated as a result of multiple diffraction, and their intensity depends on the degree of mutual orthogonality of hologram object waves. 相似文献
9.
Lamb waves at the fundamental, and of higher orders, can be excited with sufficient intensity for lamination detection in thick plates if large-area probes and long acoustic pulses are used. Hot-rolled steel plates up to 16mm in thickness can be tested, and clear and unambiguous results obtained. 相似文献
10.
The scanning of a one-dimensional light intensity distribution was accomplished by employing the acousto-optic interaction of surface waves on LiNbO3. The acoustic signal was 200 nano-seconds long with a center frequency of 100 MHz. To produce a large interaction length, the light propagates through the crystal parallel to the surface on which the acoustic surface wave is launched. The detected diffraction signal yields a temporal representation of the spatial intensity distribution. 相似文献
11.
Acoustooptic Bragg diffraction without overemodulation (i.e., with the extended high-efficiency region on the diffraction
efficiency dependence vs. sound amplitude) is studied theoretically and experimentally. It is found that this effect appears
in the case of a symmetrically nonuniform acoustic field and is due to the equality of additional opposite phase shifts of
light beams passing through symmetric regions of the acoustic field. The situation is considered when an acoustic field is
excited by a three-section phased-array transducer. The conditions are determined, in which reverse optical power transfer
from the diffracted beam to transmitted beam (overemodulation) in the case of a high (close to 100%) diffraction efficiency
is considerably suppressed. In the case of a phased array, the effect weakly depends on the frequency of sound and the size
of transducer sections, which makes it possible to observe it in a wide range of acoustooptic interaction parameters. 相似文献
12.
A Particle-in-Cell Simulation Study on Harmonic Waves Excited by Electron Beams in Unmagnetized Plasmas 下载免费PDF全文
《中国物理快报》2016,(8)
The excitation of harmonic waves by an electron beam is studied with electrostatic simulations.The results suggest that the harmonic waves are excited during the linear stage of the simulation and are developed in the nonlinear stage.First,the Langmuir waves(LWs)are excited by the beam electrons.Then the coupling of the forward propagating LWs and beam modes will excite the second harmonic waves.The third harmonic waves will be produced if the lower velocity side of the beam still has a positive velocity gradient.The beam velocity decreases at the same time,which provides the energy for wave excitation.We find that it is difficult to excite the harmonic waves with the increase of the thermal velocity of the beam electrons.The beam electrons will be heated after waves are excited,and then the part of the forward propagating LWs will turn into electron acoustic waves under the condition with a large enough intensity of beam electrons.Moreover,the action of ions hardly affects the formation of harmonic waves. 相似文献
13.
V. Gh. Mirzoyan A. A. Yeghiazaryan V. N. Aghabekyan P. V. Mirzoyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2008,43(2):67-71
X-ray diffraction on different atomic planes of an AT-cut quartz crystal is studied experimentally in the Laue geometry in case of excitation by acoustic waves at the first resonant (fundamental) frequency. Acoustic waves lead to an increase in the integral intensity of the reflection-diffracted beam. The amplification coefficients in reflection are measured in dependence on the amplitude of a.c. voltage applied to the crystal at the resonant frequency. The frontal distributions of the intensity of the beam diffracted in the reflection direction are obtained for different atomic planes. 相似文献
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15.
The acousto-optic interaction with leaky surface acoustic wave radiation into the bulk of YX-cut LiTaO3 crystals has been investigated. The light incidence and diffraction angles corresponding to the strongest acousto-optic interaction were calculated and measured as functions of the acoustic wave frequency. The dependencies of the diffracted light intensity on the amplitude of radio-frequency voltage applied to the interdigital transducer (IDT) were studied. Our acousto-optic measurements revealed generation, by the IDTs, of slow shear bulk acoustic waves propagating at different angles depending on their frequency. A secondary acousto-optic interaction from the bulk waves radiated by the receiving IDT has been studied. 相似文献
16.
S. N. Antonov 《Technical Physics》2005,50(1):104-106
Acoustooptic Raman-Nath diffraction by a standing acoustic wave in a paratellurite crystal is investigated. An acoustic line
is made in the form of a polished cube and serves as a high-Q acoustic resonator. A slow shear wave is excited by a single piezoelectric transducer. Multiple lossless sound reflections
lead to two-coordinate light diffusion. When the acoustic intensity introduced into the crystal is about 2 W/cm2 at a sound frequency of 7 MHz, there appears a diffraction pattern in the form of a homogeneous light spot with a solid angle
of about 0.5 sr. An explanation for the features of the acoustooptic interaction is given. It is shown that this type of diffraction
is helpful in designing acoustooptic two-coordinate diffusers of light beams. 相似文献
17.
Collinear light diffraction by three-frequency sound is investigated theoretically. The amplitude distributions of transmitted and diffracted light waves along the cell are calculated for different amplitudes of sound signals. The dependence of the intensity of principal diffraction peaks on the frequency difference between acoustic signal components is studied for different amplitude ratios of these components. It is shown that the character of this dependence for a wave being in synchronism differs substantially from that for two other waves characterized by detuning. The dependence of the amplitudes of principal and parasitic diffraction peaks on the efficiency of acoustooptical interaction is investigated. It is demonstrated that parasitic sideband components in diffracted light can play a considerable role if the diffraction efficiency is sufficiently high and exceeds 80%. 相似文献
18.
We have calculated the intensities of ultrasonic waves excited by counter-propagating light waves of different frequencies
and scattered by spherical defects in absorbing isotropic media. We have analyzed the intensity of the scattered sound as
a function of the scattering angle and the position of the defect relative to the entry face of the acoustic waveguide. We
have shown that for hollow spherical defects, the intensity of the scattered sound tends toward zero for scattering angles
close to 90o, and for significantly smaller angles for dense inclusions.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 5, pp. 686–689, September–October, 2006. 相似文献
19.
通过采用将入射光掠入射到频率为几百赫兹的衰减低频液体表面波上,观察到了清晰的间距分布具有明显非对称性的衍射条纹。当入射光掠入射到低频液体表面上时,衍射图样非对称分布具有普遍性。理论上得到了考虑表面波衰减影响后观察屏处衍射光强分布的解析表达式。理论结果表明:衍射图样的这种非对称分布与衍射级次、入射光波波长、液体表面波波长及表面波衰减系数有关;正负级次衍射亮条纹距离中央零级亮条纹的间距体现表面波衰减信息;正衍射级次之间以及负衍射级次之间的条纹间距体现表面波波长信息。利用所提出的方法实现了对几百赫兹液体表面波的衰减系数的实时便捷测量。 相似文献
20.
A. Gedeon 《Applied physics. B, Lasers and optics》1973,2(1):15-22
Efficient focussing of surface acoustic waves has been achieved using a properly shaped gold film deposit on the −22.3° rotated
Y-cut surface of quartz. The acoustic wave field was studied with laser probing techniques. A more than threefold increase
in intensity and a tenfold decrease in beam width was observed at the focal point. The focussing action was obtained with
the elastic wave equivalent of the Fresnel phase-reversal zone plate of optics. The multiple foci of this device allowed a
simultaneous generation of acoustic waves in nearly all directions on the surface. Consequently, the surface wave velocity
anisotropy could be determined completely. The experimental results are in very good agreement with the calculated velocity
anisotropy. Electromagnetic diffraction theory is adopted to the two dimensional anisotropic system to analyse the performance
of the focussing device. 相似文献