【作者】 刘峰；

【导师】 郭庆林；

【作者基本信息】 河北大学 ， 光学， 2003， 硕士

【摘要】 本文以He-Ne激光为光源，采用实时光探测数据采集处理系统，系统的研究了Ce：KNSBN晶体的两波耦合稳态特性及两波耦合过程中信号光、泵浦光和光扇的时间演化，同时对泵浦光斩波两波耦合过程进行了分析。论文给出了不同写入光强比、写入总光强、写入光夹角及偏振光下Ce：KNSBN晶体的两波耦合增益系数、衍射效率、响应时间的变化规律。通过拟合响应时间随写入光夹角变化关系，获得了一种确定光折变晶体有效电光系数Rr_eff和有效光折变电荷密度N_eff参数的新方法。在不同写入光强比和写入总光强下，获得了Ce：KNSBN晶体两波耦合过程中信号光及泵浦光的时间演化曲线，分析了光扇的时间演化和光扇效应对两波耦合动态过程的影响。实验发现在e偏振光写入情况下，Ce：KNSBN晶体中光扇存在写入光强度阈值特性，当写入光强大于20mW／cm²时光扇效应明显增强。对实验观察到信号光打开时间延迟将导致两波耦合能量增益曲线峰值增益降低的现象，从光扇时间演化角度进行了合理的解释。在斩波调制的两波耦合实验中发现：泵浦光斩波调制将延缓Ce：KNSBN晶体中光扇发展。依据实验结果对考虑光扇的耦合波方程进行了实验修正，并对两波耦合动态过程的时间演化进行了数值解模拟，计算结果与实验基本吻合。本文实验结果和理论分析为研究高增益光折变材料的光折变特性和在全息光存储和光学信息处理等领域的实际应用提供了基础性的实验依据。更多还原

【Abstract】 In this research, the steady and temporal properties of Two waves mixing (TWM) were studied in a Ce:KNSBN crystal with a He-Ne laser and a synchronous data recording system, and the process of TWM was analyzed under a bump beam chopped condition. As the results, firstly, some steady parameters were determined, including the gain coefficient г, diffraction efficiency of the volume grating η and response time t1 of TWM under different total incident intensity I0, ratio of two writing beams mo, angle between two writing beams 2θ and polarization conditions. Secondly, a new method was proposed to obtain two important coefficients of the Ce:KNSBN crystal, Rreff and Neff, by fitting the variation of response time as a function of 2θ . Thirdly, the temporal behavior of the pump beam, signal beam and fanning and the influence of fanning to TWM were carefully studied and analyzed under different incident conditions in TWM. Fourthly, the incident intensity threshold of the fanning effect in TWM was measured inthe Ce:KNSBN crystal, and it is about 20mW/cm , while using 632.8nm red light with e polarization as writing beam. Fifthly, a reasonable explanation to the phenomenon was given that the temporal behavior of TWM will be different while the signal beam opening time delays a different time after pump beam opened. Sixthly, in the experiment under a pump chopped condition, we found that a chopped pump will weaken the fanning development at the beginning of TWM. Finally, wave-coupling equations modified according to experiments, were implemented to simulate the dynamic process of the TWM and the theoretical calculated results are coincident with the experimental data. These results are helpful for understanding the photorefr active dynamic of TWM in Ce:KNSBN crystal and the influence of fanning to TWM, and provides fundamental data for the applications of doped KNSBN crystal in the fields of optical information processing and holographic storage.更多还原