摘要
通过飞秒脉冲激光单光束Z 扫描方法研究了聚 10,12 二十五碳双炔酸Langmuir Schaefer膜在非共振吸收区的三阶非线性光学特性。钛蓝宝石激光器的输出脉宽为60～70fs、波长为800nm,在入射光平均功率为145mW时测得其三阶非线性极化率为5.33×10-9esu。这一结果较该类材料的有掺杂的薄膜明显增强,与微晶和单晶达到同样的量级,对此进行了分析和讨论。
Polydiacetylene with the substantial π-electron delocalization along the main chain backbones is one promising nonlinear material for application and fundamental properties of nonlinearity. Utilizing LS technology, uniform thin film with a desired thickness can be obtained easily and inexpensively, which makes convenience for optical device applications. Therefore many attempts have been performed to improve nonlinear optical (NLO) properties of polydiacetylene LS film. In this paper, an eight-monolayer film of poly-10, 12 pentacosadiynoic acid (poly-PCDA) about 26 nm thick was prepared on glass substrate using Langmuir-Schaefer method. Then, the third-order NLO properties of poly-PCDA were investigated by Z-scan technique using a femtosecond pulse laser with the pulse duration of 100 fs at 800 nm. A self-focused effect was observed. And the nonlinear refractive index γ, TPA coefficient β, real part of third-order NLO susceptibility Reχ^((3)) and imaginary part of third-order NLO susceptibility Imχ^((3)) of ploy-PCDA were calculated. A very large value of third-order NLO susceptibility χ^((3)) =5.33×10^(-9)esu was detected under the average incidence power of 145 mW. This magnitude reaches the same order as that of polydiacetylenes crystal or mictocrystal. We investigated the factors contributed to third-order NLO susceptibility and ascribed primarily them to two factors. First, π-electron aberrance induced by femtosecond laser can be a key mechanism for the third-order NLO poly-PCDA LS film. Second, a large conjugated system requires that the molecule should be as planar as possible without too much torsion or distortion of monomer units in the chain. In our case, longer conjugated chain may form without ligand interference. The high nonlinearity and uniform large area film makes poly-PCDA LS film particularly interesting and attractive for optical device designs.
出处
《发光学报》
EI
CAS
CSCD
北大核心
2004年第5期575-579,共5页
Chinese Journal of Luminescence
基金
国家自然科学基金资助项目(60077015
69886003
69877019)
