Feng Yanyan, Dong Ningning, Wang Gaozhong, Li Yuanxin, Zhang Saifeng, Wang Kangpeng, Zhang Long, Blau Werner J, Wang Jun
Opt Express. 2015 Jan 12;23(1):559-69. doi: 10.1364/OE.23.000559.
A comparative research on saturable absorption (SA) behavior dependence on wavelength and pulse duration was performed for graphene polymer composites. Free-standing graphene-polyvinyl alcohol (PVA) composite films were fabricated by using solution cast method in combination of liquid phase exfoliation. SA responses were observed by using an open-aperture Z-scan technique for 340 fs pulses at 1030 nm and 515 nm from a mode-locked fiber laser, and 6 ns pulses at 1064 nm and 532 nm from a Q-switched Nd:YAG laser. The graphene films possess better SA property, i.e., larger SA coefficient and figure of merit (FOM), and lower saturation intensity I(s), for ns pulses than that for fs pulses at the similar near infrared (NIR) wavelength. For fs pulses, the films show better SA response at 1030 nm than that at 515 nm. By employing slow and fast SA modelling, the excited state and ground state absorption cross sections were estimated to be ~10(-17) cm(2), and the ratio was ~0.6 at NIR for both fs and ns pulses.
对石墨烯聚合物复合材料的饱和吸收（SA）行为随波长和脉冲持续时间的依赖性进行了比较研究。采用溶液浇铸法结合液相剥离法制备了独立的石墨烯-聚乙烯醇（PVA）复合薄膜。利用开孔Z扫描技术，分别对锁模光纤激光器输出的1030nm和515nm波长的340fs脉冲，以及调Q Nd:YAG激光器输出的1064nm和532nm波长的6ns脉冲进行了SA响应观测。在相似的近红外（NIR）波长下，对于纳秒脉冲，石墨烯薄膜具有更好的SA特性，即更大的SA系数和品质因数（FOM），以及更低的饱和强度I(s)，相比飞秒脉冲而言。对于飞秒脉冲，薄膜在1030nm处的SA响应优于515nm处。通过慢饱和吸收和快饱和吸收建模，估计在近红外波段，飞秒脉冲和纳秒脉冲的激发态和基态吸收截面均约为10(-17) cm(2)，二者的比值约为0.6。
