共查询到20条相似文献,搜索用时 510 毫秒
1.
M. Shamonin 《Applied Physics A: Materials Science & Processing》1993,57(2):153-156
A theory describing threshold conditions for spontaneous generation of spatial subharmonics in a photorefractive crystal with an externally applied square-wave ac voltage is presented. Predicted results are in good agreement with the experimental data. 相似文献
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M. V. Gorkunov E. V. Podivilov B. I. Sturman 《Journal of Experimental and Theoretical Physics》2002,94(3):470-481
It is shown that when approaching the spatial subharmonics generation threshold in fast photorefractive crystals (the sillenites, CdTe), a practically unlimited (singular) amplification of the nonlinear photorefractive response is possible, which results in a drastic increase in the spatial amplification of weak signals. A theory of critical spatial amplification is developed. This theory takes into account real attributes of fast photorefractive crystals such as the vectorial nature of wave coupling and nonuniform broadening of resonances owing to light absorption. The theory is applied to the analysis of the observable characteristics of critical enhancement and to optimization of the conditions of experiments aimed at the detection and investigation of this phenomenon. 相似文献
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K. Shcherbin 《Applied physics. B, Lasers and optics》2000,71(1):123-127
The generation of spatial subharmonics is reported in a photorefractive semiconductor (CdTe:Ge) for the first time to our
knowledge. Space charge waves with a narrow spatial spectrum are detected in homogeneously illuminated ac-biased CdTe:Ge sample
by observation of a well developed low divergent self-diffracted beam. The mobility-lifetime product of the free carriers
and the effective trap concentration are estimated from the threshold ac-field measured for different subharmonics at different
grating vectors of the generated grating.
Received: 5 April 2000 / Published online: 7 June 2000 相似文献
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为了得到光折变晶体中非相干耦合空间孤子对统一理论的结果,基于单光子光折变空间光孤子的基本理论模型,建立了稳态条件下有分压电阻和e偏振非相干均匀背景光辐照的单光子光伏光折变晶体中非相干耦合空间孤子对理论. 研究表明:这种孤子对是由两束偏振方向和波长都相同的互不相干光束耦合形成的, 孤子对两光束都能在晶体中稳定传播;当分压电阻、e偏振背景光、外加电场和光伏场取不同值时, 可获得14种光折变非相干耦合空间孤子对. 本文的结果对完善和充实光折变空间孤子理论体系有重要意义. 相似文献
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为了得到光折变晶体中非相干耦合空间孤子对统一理论的结果,基于单光子光折变空间光孤子的基本理论模型,建立了稳态条件下有分压电阻和e偏振非相干均匀背景光辐照的单光子光伏光折变晶体中非相干耦合空间孤子对理论.研究表明:这种孤子对是由两束偏振方向和波长都相同的互不相干光束耦合形成的,孤子对两光束都能在晶体中稳定传播;当分压电阻、e偏振背景光、外加电场和光伏场取不同值时,可获得14种光折变非相干耦合空间孤子对.本文的结果对完善和充实光折变空间孤子理论体系有重要意义. 相似文献
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M.P. Petrov V.V. Bryksin S. Wevering E. Krätzig 《Applied physics. B, Lasers and optics》2001,73(7):699-703
For the first time the effects of overall doubling, spatial doubling, and overall rectification of space charge waves in a
photorefractive crystal (Bi12GeO20, BGO) have been detected and theoretically studied. The effects of overall doubling and overall rectification resemble second-harmonic
generation and rectification of light in nonlinear optics. A good agreement between theory and experiment is found for the
effect of spatial doubling, while for overall doubling and overall rectification effects only a qualitative agreement between
theory and experiment has been established until now.
Received: 13 July 2001 / Published online: 10 October 2001 相似文献
7.
LU Keqing ZHANG Yanpeng TANG Tiantong HOU Xun WU Hongcai Department of Electronic Science Technolog Xi’an Jiaotong University Xi’an China Department of Applied Physics Xidian Un 《Chinese Journal of Lasers》2001,10(3):223-227
1 Introduction Steady statephotorefractive (PR)spatialsolitons[1~ 3] havebeeninvestigatedextensivelyinthepastfewyears.Atpresentthesearetwodifferentkindsofsteady statePRsolitons :screening[1 ,2 ] solitonsandphotovoltaic (PV) [3]solitons.Morerecently ,wehaveshowntheo… 相似文献
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有偏压中心对称光折变晶体中的屏蔽孤子 总被引:7,自引:6,他引:1
给出了中心对称光折变晶体中屏蔽孤子的高阶空间电荷场.当高阶项可以忽略时,这个电荷场就变为早前在中心对称光折变晶体中研究的屏蔽孤子的空间电荷场.研究了中心对称光折变晶体中屏蔽孤子的高阶非线性波动方程.在适当的条件下,这个非线性波动方程能够展示明暗空间光孤子.这类晶体不同于非中心对称晶体,其非线性折射率的改变来源于二次电光效应,而不是一般的线性电光效应.应用光束传播的方法,对这些孤子的稳定性进行了讨论.表明在小的微扰下这类孤子是稳定的,不会发生分裂. 相似文献
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P. M. Lushnikov 《Journal of Experimental and Theoretical Physics》1998,86(3):614-627
A nonlinear theory is presented for the formation of hexagonal optical structures in a photorefractive medium equipped with
a feedback mirror. Oppositely directed beams in photorefractive crystals are unstable against the excitation of sideband waves.
It is shown here that as this instability evolves to its nonlinear stage, the three-wave interaction between weak sideband
beams does not stabilize it, but rather leads to explosive growth of the amplitudes of beams whose transverse wave vectors
form angles that are multiples of π/3. As a result, sideband beams at these angles are found to be correlated. A range of parameters is found in which four-wave
interactions saturate the explosive instability, which explains the appearance of stable hexagons in the experiment. Outside
this region, nonlinearities of higher order saturate the explosive instability, and the process of hexagon generation must
be studied numerically. Matrix elements are obtained for the three-and four-wave interactions as functions of the distance
to the feedback mirror, and an equation for the time evolution of the sideband wave amplitudes is derived that describes the
hexagon generation. A comparison is made with experimental results for the photorefractive crystals KNbO3 and BaTiO3.
Zh. éksp. Teor. Fiz. 113, 1122–1146 (March 1998) 相似文献
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The features of the nondiffractive propagation of light beams in photorefractive semiconductors under conditions for manifestation
of the Franz-Keldysh effect are investigated. It is shown that the combined influence of electrorefraction and electroabsorption
in such materials leads to the formation of inhomogeneous spatial solitons, for which the directions of energy propagation
and the phase velocity are different. The dependence of the soliton shape on the parameters of the photorefractive semiconductor
and the external electric field strength is established.
Zh. Tekh. Fiz. 68, 80–84 (October 1998) 相似文献
17.
Holographic solitons in photorefractive dissipative systems 总被引:1,自引:0,他引:1
Liu J 《Optics letters》2003,28(22):2237-2239
A new kind of holographic soliton is proposed for a photorefractive dissipative system consisting of a biased photorefractive crystal and a strong pump beam with a uniform spatial distribution in both transverse dimensions. The self-trapping beam in the system can evolve into a spatial soliton when it couples coherently with the pump beam by two-wave mixing. Unlike the holographic solitons recently proposed by Cohen et al. [Opt. Lett. 27, 2031 (2002)], the most unique features of the present solitons are that they have a fixed amplitude and width that are determined completely by the system parameters and that their existence conditions are independent of the polarity of the bias field. Numerical simulations show that these solitons are stable relative to small perturbations. 相似文献
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用干涉法在自散焦光折变晶体 LiNbO3:Fe中写入光子晶格的动态过程中,发现了双光束干涉条纹一分为二,四光束干涉点阵一分为四的分裂现象. 研究证明:这是干涉条纹空间频率的倍频现象,是入射的干涉光场与写入的光子晶格之间相互作用的结果. 本实验说明利用光折变效应可以容易地实现干涉光场空间频率的倍频和空间高次谐波的产生,并可利用产生的空间谐波感应出二倍频和高倍频的光折变光子晶格.
关键词:
光折变晶体
光子晶格
空间谐波 相似文献
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光折变介质中空间光孤子自弯曲现象研究 总被引:1,自引:0,他引:1
光折变非线性介质在外加直流电压时会引起介质内部电荷移动,而移动后的电荷又会导致空间电荷的扩散效应,从而产生非局域非线性现象。从理论上研究了具有流动和扩散非局域非线性的光折变晶体中所支持的空间光学孤子的传播行为。应用等效粒子近似方法分析了这类介质中(1 1)维空间光学孤子动力学行为,得出孤子运动"加速度"显式解。孤子的有效"加速度"决定于孤子参量和光折变非局域参量。所得的解析结果可在一定参量范围内直接用来计算孤子的传播轨迹。对孤子在光折变非局域非线性作用下的传播动力学行为做了仿真模拟,数值模拟结果与理论分析结论符合得很好。 相似文献