共查询到20条相似文献,搜索用时 15 毫秒
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The incident photon-energy dependence of the Brillouin-scattering intensity from acoustic waves injected into GaP is studied at room temperature in the photon-energy range 2.175–2.27 eV. It is found that the Brillouin-scattering cross-section resonantly cancels near the indirect absorption edge. The observed cancellation can be accounted for by the resonant contributions arising from the resonance between the incident photon-energy and the indirect-energy gap. 相似文献
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受激布里渊散射(SBS)作为三阶光学效应广泛应用于激光组束、分布式光纤传感、布里渊激光器等领域。近年来,SBS脉冲压缩亦得到特殊关注。基于布里渊放大过程中的能量转移特性,SBS脉冲压缩技术能够将ns量级脉冲压缩至亚ns量级,峰值功率可提升1~2个数量级。系统介绍了SBS脉冲压缩基本理论,综合论述了SBS压缩器结构、增益介质、泵浦脉冲等因素对脉冲压缩特性的影响,并对SBS脉冲压缩发展趋势进行了展望,为今后SBS特性的研究提供了有益参考,也为高重频、高能量激光的获取提供了可行方案。
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A new approach to remote sensing of the ocean is proposed. It is based on a combination of Brillouin scattering, incoherent lidar techniques and high-resolution frequency discrimination via gas absorption cells. The results of theoretical and experimental research are given. This approach provides the capability of rapid real-time monitoring of sound-speed or temperature profiles both in the open ocean and in littoral zones with high resolution and high accuracy. PACS 42.68.Wt; 42.79.Qx; 78.35.+c 相似文献
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Calculations and measurements are presented which show that absolute scattering cross sections (“Rayleigh ratios”) can be determined by measuring the ratio of the depolarized intensity of doubly scattered light to the polarized intensity of singly scattered light. This technique should be useful in determining the susceptibilities of fluids and the molecular weights of macromolecules. 相似文献
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Depth-resolved temperature measurements of water using the?Brillouin lidar technique 总被引:1,自引:0,他引:1
Coupling between the atmosphere and the ocean takes place predominantly in the upper ocean mixed layer. Knowledge of the temperature
profile in this region is therefore of particular interest. In this paper we report a successful measurement of a temperature
distribution in a water tube based on Brillouin scattering with a fiber amplifier as the light source. It represents an important
step towards the practical implementation of a lidar system for field use. Such a system could provide cost-effective on-line
data over an extended region of the ocean and has potential impact to studies concerning climate, oceanography, weather forecasting
and hurricane movements. 相似文献
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Detecting submerged objects by Brillouin scattering 总被引:6,自引:0,他引:6
The principle of detecting submerged objects by Brillouin scattering is analyzed. It is based on testing the frequency shift rather than the intensity of the scattered signal. Experiments based on the principle are carried out. An actual detecting system for practical applications is designed, and the experimental results obtained by using the system are given. The experimental results show that the method of Brillouin scattering possesses several advantages compared to the method of testing the signal intensity. The conclusion is that Brillouin scattering is a good method for detecting submerged objects. PACS 42.68.Wt; 42.79.Qx; 78.35.+c 相似文献
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The analyzing power Aγ(θ) for neutron-proton scattering has been measured for θ = 90°(c.m.) from 13.5 to 16.9 MeV and from θ = 50° to 145°(c.m.) at 16.9 MeV. Extensive Monte Carlo calculations have been made to correct for multiple scattering effects. Overall uncertainties are about ± 0.002. All the Aγ(θ) data, but primarily those at 16.9 MeV, disagree with predictons based on the phase-shift sets which have been derived previously by way of global analyses of nucleon-nucleon scattering data. Data for the product σ(θ)Aγ(θ) have been fitted with an expansion of the form (sin θ)(. For the first time the need for a non-zero a2 has been illustrated for energies below 20 MeV. This parameter is shown to be related to the nucleon-nucleon F-state spin-orbit phase parameter. In addition, the P, D, and F spin-orbit phase parameter values derived from the present data differ significantly from the ones based on the Yale-IV and Liver-more-X global analyses. The derived D and F spin-orbit phase parameters also differ from those obtained in the recent analysis of nucleon-nucleon scattering data by Arndt et al. 相似文献
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Brillouin scattering of photons off the density fluctuations in a fluid is potentially important for cosmology. We derive the Brillouin spectral distortion of blackbody radiation, and discuss the possible implications for the cosmic microwave background. The thermal Sunyaev-Zeldovich effect is slightly modified by Brillouin distortion, but only at very long wavelengths. 相似文献
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V. T. Bublik K. D. Shcherbachev M. I. Voronova E. V. Zhevnerov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(5):773-777
Features of microdefect (MD) formation in GaAs(Si) single crystals grown by horizontally oriented crystallization were studied
by X-ray diffuse scattering (XRDS). Measurements were performed at room temperature (∼298 K) and near the liquid nitrogen
evaporation temperature (∼85 K) using an open-flow cooling nitrogen cryostat. A practical technique for measuring XRDS using
a triple-axis X-ray diffractometer was developed and applied to separate scattering on defects and thermal diffuse scattering.
For a crystal with n = 2.0 × 1018 cm−3, the radius of detected nonspherical MDs was determined as ∼0.2 μm; thermal diffuse scattering (TDS) was experimentally separated.
For a crystal with n = 3.9 × 1018 cm−3, nonspherical MDs ∼0.5 μm in radius were detected; TDS was found to be a negligible fraction of total XRDS. At the same time,
in the case of coinciding crystal orientations and identical experimental conditions, TDS measurement data for one crystal
can be used for other GaAs(Si) crystals with the same orientation. 相似文献
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Brillouin scattering is an efficient nondestructive and noncontact measurement method to obtain the wave properties of thin layers at hypersonic frequencies. The reflection induced ThetaA (RIThetaA) scattering geometry enables the simultaneous measurement of the phonons, which propagate in each direction of wave vectors of q(Theta A) (propagation in the film plane) and q(180) (back scattering). Using this scattering geometry, we could observe the refractive indices and birefringence of the piezoelectric poly-vinylidene fluoride (PVDF) film as a function of temperature. By introducing the microscopic technique, the elastic anisotropy and refractive index measurements in the minute area of polycrystalline ZnO films were also performed. 相似文献
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The dynamics of precursor polar clusters in rhodium(Rh)-doped barium titanate single crystals were examined in the paraelectric phase by Brillouin light scattering and birefringence measurements in a wide temperature range. The longitudinal acoustic (LA) mode and central peaks in the inelastic light scattering spectrum were investigated by Brillouin scattering, while the temperature dependence of the birefringence was accurately determined by means of a birefringence imaging system. In a specific temperature range above the ferroelectric phase transition temperature, the LA mode frequency exhibited a significant softening concomitant with the substantial increase in the hypersonic damping, which was attributed to the formation of polar clusters and their interactions with acoustic waves. In this temperature range where acoustic anomalies were brought about, the birefringence showed non-zero values, indicating the existence of local non-centrosymmetric regions. All these results clearly indicated that the off-centered motions of Ti ions in the oxygen octahedra in Rh-doped BaTiO3 are correlated in the paraelectric phase inducing slowing down of the precursor dynamics and anomalous birefringence, similar to pure BaTiO3 (Ko et al., Phys. Rev. B 84, 094123 (2011)). The effect of rhodium doping in BaTiO3 enhanced the first-order character of the ferroelectric phase transition. 相似文献
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Stimulated Brillouin scattering (SBS) in a perfluorinated graded-index polymer optical fiber (POF) with 120 μm core diameter was experimentally observed for the first time, to the best of our knowledge, at 1.55 μm wavelength with the pump-probe technique. Compared to spontaneous Brillouin scattering previously reported, the Brillouin gain spectrum (BGS) was detected with an extremely high signal-to-noise ratio, even with a short POF (1 m) and scrambled polarization state. We also investigated the BGS dependences on probe power and temperature, which indicate that SBS in a POF measured with this technique can be utilized to develop high-accuracy temperature sensing systems. 相似文献
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We demonstrate a reflection geometry frequency-domain technique that is suitable for measurement of the optical properties of a medium with moderate scatter and absorption (mu(s) and mu(a) ~ 1 m(-1)). Variations in absorption and scatter produce opposing tends in the amplitude signal and common trends in the phase signal, allowing unique determination of absorption and scattering coefficients for a given phase function. An analytical model based on single-scattering events gives good agreement with experimental measurements. 相似文献
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为提高液体介质中受激拉曼散射的输出能量,提出了通过温度调控来抑制受激布里渊散射的方法,设计了532 nm多纵模宽带脉冲激光泵浦的受激拉曼散射发生系统,测量了不同温度下水中前向受激拉曼散射及后向受激布里渊散射的输出能量,分析了水温、泵浦激光线宽及热散焦效应对受激拉曼散射输出能量影响的物理机制.实验结果表明:通过降低水温可实现对受激布里渊散射过程的有效抑制,同时减小热散焦效应带来的光束畸变,从而有效提高受激拉曼散射的输出能量.研究结果对液体介质中的受激拉曼散射多波长转换具有重要意义. 相似文献
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All the elastic stiffness constants of thiourea have been measured at room temperature. The value of C66(0.7 × 1010dynes/cm2) is very low. The C11 and C33 constants exhibit discontinuities at 169 and 202 K. The longitudinal acoustic phonons propagating in the c direction are very strongly damped in the vicinity of 202 K. 相似文献