二氧化钛薄膜的三阶非线性光学特性

采用脉冲激光沉积技术在熔石英基片上制备了c轴取向的锐钛矿相TiO₂薄膜.通过X射线衍射和原子力显微镜对薄膜的结构、结晶性和表面特性进行了表征.通过透射光谱计算得到TiO₂薄膜折射率约为2.1，光学带隙约为3.18eV.结合飞秒激光和Z扫描方法测量了薄膜的超快非线性光学特性，结果表明：锐钛矿TiO₂薄膜具有负的非线性吸收系数和负的非线性折射率，其大小分别为-6.2×10^-11m/W和-6.32×10^-17m²/W，对应的三阶非线性极化率的实部和虚部分别为-7.1×10^-11esu和-4.42×10^-12esu.并计算薄膜的优值比T=βλ/n₂≈0.8，表明锐钛矿相的TiO₂在非线性光学器件方面具有潜在的应用前景.

Third-order Nonlinear Optical Properties of TiO2 Films

Anatase TiO₂ films were fabricated on fused quartz by pulsed laser deposition （PLD） technique and the single-phase anatase films were obtained under the optimal conditions. The X-ray diffraction and atomic force microscope were used to investigate the structure and surface characters of the film. The third-order optical nonlinearities of the films were measured by Z-scan technique using a femtosecond laser (50fs) of 800nm. From the transmission spectra, the optical band gap and linear refractive index of the TiO₂ film are determined to be 3.18eV and 2.1, respectively. The nonlinear absorption coefficient and nonlinear refractive index are determined to be -6.2×10^-11m/W and -6.32×10^-17m²/W, respectively.The real and imaginary parts of third-order nonlinear susceptibility χ(³) are determined to be -7.1×10^-11esu and -4.42×10^-12esu, respectively. And the following figure of merit T=βλ/n₂ is calculated to be 0.8 for the film, indicating that the anatase TiO₂ films have great potential applications to nonlinear optical devices.