两种对称无氯吩恶嗪盐的三阶光学非线性及动力学探究

Third-order Nonlinear Optical Properties and Dynamics of Two Symmetrical Phenothiazinium Chloride-free Salts

通过纳秒和皮秒Z扫描技术测量了在532 nm波长激发下的两种对称无氯吩恶嗪盐的三阶光学非线性响应,发现其中Br和I在纳秒时域下的β,γandχ(3)数值比参考文献中要高一个数量级。结果表明不同的基团添加到主链上对吩恶恶嗪的非线性光学特性产生较大的调控作用。为了更深入地探究Br和I溶液的非线性来源机制,进行了532 nm波长下的皮秒时间分辨泵浦探测实验,发现样品中Br和I的σ1/σ0比值分别是9.1和8.3,都比已报道的有机盐乙腈溶液的σ1/σ0比值大。大的σ1/σ0比值以及长激发态寿命使样品比文献中报道的非对称型结构的机盐乙腈溶液拥有更好的非线性光学性能。

The third-order nonlinear optical response of two novel symmetrical phenothiazinium chloride-free salts dissolved in DMF were investigated using picosecond top-hat Z-scan and nanosecond Z-scan techniques under 532 nm wavelength excitation.We found that the amplitudes of β,γand χ（3） for 4a（Br）/DMF and 4a（I）/DMF are one order of magnitude larger than those reported in Refs at ns timescale. The experimental results clearly indicate that different groups added to main chain make an important modulation effects on nonlinear optical properties of phenothiazinium salts. To give a further knowledge of the original nonlinear mechanism of 4a（I）/DMF and 4a（Br）/DMF solution, picosecond time-resolved pump-probe experiment at 532nm has been done to further investigation. The ratio of σ1/σ0 for 4a（Br）/DMF and 4a（I）/DMF is 9.1 and 8.3, respectively. Large ratio of σ1/σ0 plus long excited-state lifetimes make this two symmetrical compounds have a better nonlinear absorption properties than organic salt/acetonitrile which has a nonsymmetrical structure.