共查询到19条相似文献,搜索用时 78 毫秒
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研究了Ce∶KNSBN光折变类光纤在泵浦光和信号光夹角分别为小角度和大角度两种情况下简并四波混频的基本特性 .当夹角较大时 ,在光折变类光纤内部形成了两个四波混频作用区域 ,获得了比小角度情况提高 4倍的大相位共轭反射率 .给出了Ce∶KNSBN光折变类光纤中 ,在入射夹角分别为小角度和大角度两种情况下 ,相位共轭光反射率分别随信号光光强、两束泵浦光光强比变化的实验结果 ,并用理论公式进行了拟合 ,理论分析和实验结果相符 .还研究了Ce∶KNSBN光折变类光纤四波混频光栅模式和相位共轭光时间响应特性 .光折变类光纤的相位共轭响应时间较快 ,可为秒量级 . 相似文献
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Mn:KNSBN晶体中弱入射光高反射率四波混频相位共轭 总被引:1,自引:0,他引:1
功率为1mW左右的He-Ne激光束在Mn:KNSBN晶体中实现四波混频相位共轭。入射光相对于晶体主光轴的取向及入射光偏振组态对相位共轭反射率都有很大的影响。当物光近于布儒斯特角入射时,反射率可达60%。建立时间约为60sec的光折变光栅具有18hr左右的寿命。晶体中观察到诱导四波混频相位共轭。 相似文献
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Cu:KNSBN晶体自泵浦与互泵浦相位共轭共存特性的实验研究 总被引:10,自引:3,他引:7
利用Cu:KNSBN晶体,研究了在两束泵浦光对称入射的条件下,自泵浦与互泵浦相位共轭共存时相互竞争和相互影响的特性,以及共存时的相位共轭特性与两束泵浦光的入射位置、入射夹角和泵浦比之间的关系,并对自泵浦相位共轭反射率和两束泵浦光共同存在条件下的自泵浦相位共轭反射率进行了比较. 相似文献
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KNSBN:Co晶体的无外场自泵浦相位共轭 总被引:2,自引:2,他引:0
利用掺Co:(KNa)_(0.2)(Sr_(0.75)Ba_(0.25))_(0.9)Nb_2O_6晶体实现了无外场,无外反射镜、无外加泵浦光束的自泵浦连续波相位共轭,其相位共轭反射率达到40%,阈值功率小于0.02W/cm~2,首次利用此晶体以梯形切割实现了光折变晶体单区域四波混频相互作用产生自泵浦位相共轭波. 相似文献
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本文报道由环形自泵浦相位共轭振荡器(采用 KNSBN:Ce 晶体)所产生的相位共轭波和47%的自泵浦反射率以及在这一装置中还观测到利用晶体缺陷对光的散射作用使变弱的共轭波增强,衍射光环增亮. 相似文献
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In the case of degenerate four-wave mixing in a cerium-doped potassium sodium strontium barium niobate (Ce:KNSBN) crystal, it is found that the transmission grating is dominant when the incident beams are extraordinarily polarized, the crystal response is more rapid, and the conjugate beam is more intense. Furthermore, the variation of the conjugate beam intensity forms a loop as the fringe modulation of the transmission grating varies. Based on this observation, we have implemented edge enhancement of an image and edge-enhanced optical correlation via four-wave mixing in a Ce:KNSBN crystal without the requirement of reversal of the signal-pump-beam intensity ratio. 相似文献
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We present a simple shooting method to obtain numerical solutions of the nonlinear coupled-wave equations for degenerate four-wave mixing in photorefractive crystals when four different types of the index gratings of unequal amplitudes are responsible for phase-conjugation. Our analysis includes the effects of pump depletion and absorption in the medium. Intensities of the four beams, both inside and at the output surface, are obtained as a function of four unequal coupling strengths and absorption coefficient. Intensity of the generated phase-conjugate beam is shown as a function of both the small and wide ranges of signal beam intensity. It is found that the multigrating operation with a careful choice of coupling constants and their combinations may improve the phase-conjugate wave generation. Also the presence of absorption reduces the phase-conjugate intensity more significantly when all the gratings are operative than when a single grating is allowed. Numerical results obtained from the computer calculations are presented in graphical form. 相似文献
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The phase conjugate reflection of double signals, induced by the self-pumped phase conjugation, is demonstrated in a 16° cut Cu-doped potassium sodium strontium barium niobate (KNSBN) photorefractive crystal. The phase conjugate reflectivities of signals were measured versus the pump-signal beam ratio. A comparison was made between the signal's reflectivity with and without the presence of the other signal beam. The multi-region four-wave mixing model within the same crystal has been employed to explain the geometry performance and the experimental results. 相似文献
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We give a theoretical analysis of a “stimulated photorefractive backscattering and four-wave mixing” (SPB-FWM) self-pumped phase conjugator (SPPC) in which the generation of the phase conjugate wave relies on both stimulated photorefractive backscattering (SPB) and four-wave mixing (FWM) processes. The two pumping beams in the FWM process are, respectively, the forward-propagating beam of which the generation is seeded by the fanning effect, and the backward-propagating beam that is generated by the SPB process. Assuming that the SPB interaction is seeded by the scattering centers in the crystal, we have calculated the threshold four-wave mixing coupling strength (γ1l1)th as a function of the SPB two-wave mixing coupling strength (γ2l2) corresponding to the 2k grating and of the reflectivity R′ of the scattering centers. Above threshold, we have also calculated the phase-conjugate reflectivity with a numerical method. Our calculations show that the threshold as well as the reflectivity of a SPB-FWM SPPC strongly depend on γ2l2 and R′. It is also shown that a high phase-conjugate reflectivity can be easily realised in doped barium titanate crystals which are shown to have much larger γ1 and γ2 than an undoped one. 相似文献
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Y.H. Ja 《Optics Communications》1982,41(3):159-163
Phase-conjugate wavefront generation via real-time holography in degenerate four-wave mixing experiments in photorefractive crystals Bi12GeO20 is presented. The phase volume hologram responsible for the phase-conjugate wavefront generation is a reflection hologram. No external electric field is applied and electron diffusion is the main mechanism responsible for the formation of the hologram. The theoretical and experimental results for wavefront reflectivity as a function of the intensity ratio of the writing beams are given. 相似文献
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We investigate the effect of beam coherence on four-wave mixing via reflection gratings in photorefractive media. For the
case of phase conjugation, the results of our theoretical analysis indicate that partial coherence always leads to a drop
of signal gain and phase conjugate reflectivity in non-depleted cases. In general, the mutual coherence of the signal beam
and the pump beam can be enhanced due to the process of wave mixing. The mutual coherence of the phase conjugate beam and
one of the pump beams depends on the beam intensity ratio as well as the optical path difference. This is distinctly different
from the four-wave mixing case with a transmission grating.
Received: 15 October 1999 / Revised version: 26 June 2000 / Published online: 7 February 2001 相似文献