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主要从实验和理论两个方面,探讨了强受限尺寸区域内不同尺寸对CdSe量子点线性和非线性光学性质的影响.用吸收光谱研究了量子点尺寸与吸收峰之间的关系,用皮秒Z扫描技术研究了共振和非共振情况下(激发光波长分别为532和1064 nm),尺寸与三阶非线性极化率之间的关系.基于电子能量状态理论和局域场增强理论对量子点进行分析,得到了CdSe不同尺寸的三阶非线性效应,研究了尺寸对量子点非线性光学性质的影响.结果表明,由激发态粒子数布局改变和纳米颗粒增大引起的非线性共振增强效应相当,二者共同作用使得三阶极化率增强20倍左右,且用532 nm的共振频率激发4.3 nmCdSe量子点时,χ(3)具有最大值2.0×10-11esu.
The effects of different sizes in strongly confined size region on the linear and nonlinear optical properties of CdSe QDs are discussed mainly from two aspects of experiment and theory.The relationship between quantum dot size and absorption peak is studied by absorption spectra, Z scan technique was used to investigate the relationship between the size and the third-order nonlinear polarizability under both resonant and nonresonant conditions (excitation wavelengths of 532 and 1064 nm, respectively). Based on the electron energy state theory and local field enhancement theory, The third order nonlinear effect of different sizes of CdSe was obtained and the effect of size on the nonlinear optical properties of quantum dots was investigated.The results show that the nonlinear resonance caused by the change of the number of excited states particles and the increase of nanoparticles The effect of the two is similar, the third-order polarizability is enhanced by about 20 times, and when the 4.3 nm CdSe quantum dots are excitated with the resonance frequency of 532 nm, the maximum value of x (3) is 2.0 × 10-11esu.