两种新型DMIT材料的三阶非线性光学性质的研究

【作者】 冯林；

【导师】 任诠；

【作者基本信息】 山东大学 ， 光学工程， 2006， 硕士

【摘要】 随着光纤通信技术的发展和密集波分复用（DWDM）系统的应用，全光网络成为宽带通信网未来的发展目标。光开关和光开关阵列是全光网络中的关键的器件之一。它对于实现光域优化、路由选择、波长选择，光交叉连接及网络的自愈保护等功能是必不可少的。虽然在传统的光开关技术之外，目前已涌现出许多新的技术，但开关速度仍然不高。因此需要研究具有极高信息传输速率的全光开关。 全光开关对材料的要求是其三阶非线性折射率要大，线性吸收和非线性吸收系数要小。三阶非线性折射率大，则需要的控制光功率密度就不用很高。线性吸收和非线性吸收系数小，就可以降低信息传输损耗，还可以减小热效应的影响，提高系统可靠性。在大量的材料中筛选适合全光开关应用的材料，需要对材料的线性和非线性光学性能进行表征，而得到的参数又可以对材料的探索、改进和全光开关器件的研制提供参考和依据。本文的主要工作如下： 1．合成了两种新的dmit材料MeCu和HtCu。通过对国内外全光开关材料的研究现状的分析，我们发现dmit盐是一类很重要的金属有机电荷转移盐，从这类材料的分子结构式上可以看到它们具有优良的π电子共轭体系，离域π电子很容易带来大的三阶非线性光学响应，另外中心金属离了也可进一步增强三阶非线性光学效应。我们测量了它们的线性吸收光谱，发现它们在通信波段（1300nm-1550nm）线性吸收很小。 2．搭建了在1064nm处的皮秒激光Z扫描实验装置，用LabVIEW软件编程来自动控制数据的采集和存储，并给出了比较详细的数据处理方法和过程。Z扫描技术是一种简单可靠的测量材料三阶非线性折射率和非线性吸收的方法，我们给出了这种方法的比较详细的公式推导，以及计算非线性折射率n₂，非线性极化率x³和分子二阶超极化率γ的方法。自动控制程序的应用，方便了实验的操作，提高了测试的准确度。 3．运用Z扫描技术对MeCu和HtCu的三阶非线性折射和非线性吸收进行了表征和研究，分析了材料的非线性光学机理，并评估了它们在全光开关器件制备更多还原

【Abstract】 With the development of optical fiber communication and the application of dense wavelength division multiplex （DWDM） technique, all-optical network is expected to be the target for the broad-band communication in the near future. Optical switches and their arrays are among the key apparatuses in all-optical network. In addition to traditional optical switching technologies, many new ones have come forth, none of whose processing speed is high enough to satisfy the requirement of this network. All-optical switches, as a result, are in demand.According to the requirement of all-optical switches, material suitable for them should possess high third-order nonlinear refractive index, low linear absorption and nonlinear absorption. Dmit salts are an important kind of organic metal charge-transfer complex. The π-electron delocalization in a conjugated systems and the d-orbit of transition metal contribute to the large third-order nonlinearity and ultrafast response capability together. Two novel dmit salts （MeCu and HtCu） were synthesized and linear absorption spectra of the sample solutions were recorded.The third-order nonlinearities were investigated by the Z-scan technique, a simple, sensitive, single-beam method to determine both the nonlinear refractive index and nonlinear absorption coefficient of a given material, at a wavelength of 1064 nm with laser duration of 30 ps. Z-scan spectra reveal their negative Kerr coefficients at 1064nm and no nonlinear absorptions were observed. The nonlinear refractive index n₂ and the second hyperpolarizability γ have been determined to be 2.15×10^-11 esu and 3.23×10^-31 esu respectively for MeCu and 6.2×10^-12 esu and 9.2×10^-32 esu respectively for HtCu.That the difference between the peak and valley transmittance ΔT_p-v is proportional to the light intensity shows that the thermal-induced nonlinearity can be neglected in our experiments. Under the same light intensity, ΔT_p-v is proportional to the concentration of the solutions, indicating that the valley and peak in the Z-scan curves originated from the material, not from the solvent or the更多还原