BNT铁电薄膜的飞秒三阶非线性光学性能研究

发布时间：2018-05-09 15:16

本文选题：BNT铁电薄膜 + 非线性光学　；参考：《湘潭大学》2015年硕士论文

【摘要】：非线性光学材料因其在信号处理、超快光通信、数据存储、光限幅器件、逻辑器件、光开关、图像传输和微加工等领域的应用而受到广泛的关注。目前,非线性光学材料的研究进展很大程度上取决于新的具有强非线性光学效应材料的发现以及对非线性光学性能的改进。铁电薄膜具有高的透过率、快的响应速度和大的非线性光学系数,是一类优异的非线性光学材料,有望在未来应用于光子器件。本文利用单光束Z扫描方法测试了Bi3.15Nd0.85Ti3O12(BNT)铁电薄膜在飞秒激光作用下的超快三阶非线性光学性能,并对其非线性光吸收特性进行了调控,主要的研究工作和结果如下:1.飞秒激光单光束Z扫描测试系统的搭建为了研究BNT铁电薄膜的非线性光学性能,我们基于波长800 nm、脉宽300fs的钛宝石飞秒激光系统搭建了单光束Z扫描测试系统,并通过CS2标准样品和石英衬底的测试检验了系统的可靠性和稳定性。2.BNT薄膜的超快三阶非线性光学性能研究首先,采用溶胶-凝胶方法在石英衬底上制备了BNT薄膜,表征了其晶体结构和线性光学性能。结果显示,所制备的BNT薄膜呈a-轴择优取向生长,具有高的光学透过率和大的禁带宽度。然后,利用上述搭建的单光束Z扫描系统测试了BNT薄膜的非线性光吸收和光折射特性,发现BNT薄膜在飞秒激光作用下具有大的三阶非线性光学系数,其双光子吸收系数为1.15×102 cm/GW,三阶非线性折射率为-8.15×10-3 cm2/GW。分析认为,BNT薄膜的超快双光子吸收效应是一个间接的电子跃迁过程,其大的非线性光折射系数可能是电子极化和铁电极化共同作用的结果。3.BNT薄膜的三阶非线性光吸收特性的调控研究首先,采用脉冲激光沉积法在石英衬底上制备了不同厚度(106.8 nm,139.7nm和312.9 nm)的BNT薄膜,表征了其晶体结构和线性光学性能。结果显示,所制备的BNT薄膜呈c-轴择优取向生长;随着薄膜厚度的增加,禁带宽度从4.02eV减小到3.68 eV。然后,通过开孔Z扫描测试研究了薄膜厚度对BNT薄膜非线性光吸收特性的影响。发现,随着薄膜厚度的增加,BNT薄膜的非线性吸收从饱和吸收转变为反饱和吸收;随着薄膜厚度的进一步增加,其反饱和吸收性能增强。分析认为,BNT薄膜的三阶非线性光吸收转变可能是基态激发和双光子吸收之间竞争的结果,这种竞争可以通过禁带宽度和缺陷态浓度进行调控。
[Abstract]:Nonlinear optical materials are widely used in signal processing, ultra-fast optical communication, data storage, optical limiter, logic devices, optical switches, image transmission and micro-processing. At present, the research progress of nonlinear optical materials depends to a great extent on the discovery of new materials with strong nonlinear optical effects and the improvement of nonlinear optical properties. Ferroelectric thin films have high transmittance, fast response speed and large nonlinear optical coefficients. Ferroelectric thin films are a kind of excellent nonlinear optical materials, which are expected to be used in photonic devices in the future. In this paper, the ultrafast third-order nonlinear optical properties of Bi3.15Nd0.85Ti3O12 BNTs under femtosecond laser are measured by a single beam Z-scan method. The nonlinear optical absorption characteristics of Bi3.15Nd0.85Ti3O12BNTs are regulated. The main work and results are as follows: 1. In order to study the nonlinear optical properties of BNT ferroelectric thin films, a femtosecond femtosecond laser system based on wavelength 800nm and pulse width 300fs has been constructed. The reliability and stability of the system were tested by CS2 standard samples and quartz substrates. Secondly, the ultrafast third-order nonlinear optical properties of BNT thin films were investigated. Firstly, BNT thin films were prepared on quartz substrates by sol-gel method. The crystal structure and linear optical properties were characterized. The results show that the prepared BNT thin films exhibit a- axis preferred orientation, high optical transmittance and wide band gap. Then, the nonlinear optical absorption and refraction characteristics of BNT thin films are tested by using the single beam Z-scan system. It is found that BNT thin films have large third-order nonlinear optical coefficients under femtosecond laser. The two-photon absorption coefficient is 1.15 脳 10 ~ (2) cm / GW, and the third-order nonlinear refractive index is -8.15 脳 10 ~ (-3) cm ~ (-2) GW. It is considered that the ultrafast two-photon absorption effect of BNT thin films is an indirect electron transition process. Its large nonlinear photorefractive coefficient may be the result of the interaction of electron polarization and iron polarization. 3. The regulation of the third-order nonlinear optical absorption characteristics of BNT thin films. BNT thin films with different thickness (106.8 nm ~ 139.7 nm and 312.9 nm) were prepared on quartz substrate by pulsed laser deposition. The crystal structure and linear optical properties of the films were characterized. The results show that the prepared BNT thin films are c-axis oriented, and the band gap decreases from 4.02eV to 3.68eV with the increase of the thickness of the films. Then, the effect of film thickness on the nonlinear optical absorption of BNT thin films was studied by Z scan. It is found that the nonlinear absorption of BNT films changes from saturation absorption to reverse saturation absorption with the increase of film thickness, and the reverse saturation absorption property increases with the further increase of film thickness. It is considered that the third-order nonlinear optical absorption transition of BNT films may be the result of competition between ground state excitation and two-photon absorption, which can be regulated by the band gap and the concentration of defect states.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.2

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