nc-Ge/SiNx多层膜材料的可调控非线性光学特性  

Tunable Nonlinear Optical Properties of nc-Ge/SiN_x Multilayers

作　　者：李悰[1,2] 张培[2,3] 姜利英[3] 陈青华[3] 闫艳霞[3] 姜素霞[3] 

机构地区：[1]中国电子科技集团公司第三十八研究所,安徽合肥230088 [2]固体微结构物理国家重点实验室,江苏南京210093 [3]郑州轻工业学院电气信息工程学院,河南郑州450002

出　　处：《发光学报》2016年第10期1217-1222,共6页Chinese Journal of Luminescence

基　　金：国家自然科学基金(61002007,61271147,11274155);郑州轻工业学院博士科研基金(2014BSJJ04);南京大学固体微结构物理实验室开放课题(M28030);基于集成共面薄膜金电极的核酸适体传感器项目(2014XJJ019)资助

摘　　要：采用等离子体增强化学气相沉积和后退火的方法制备了纳米锗/氮化硅(nc-Ge/SiN_x)多层薄膜。借助Raman光谱仪对其微结构进行表征,测得样品的晶化率大于46%。由样品的光吸收谱可知,nc-Ge的尺寸越小,其光学带隙越大。利用Z扫描技术对样品的非线性光学特性进行研究,以波长为1 064 nm、脉宽为25 ps的锁模激光作为激发光,测得样品的非线性折射率系数在10^(-10)cm^2/W数量级。实验结果表明,通过改变nc-Ge的尺寸可以使材料的非线性光学折射率由自散焦转变为自聚焦特性,而负的非线性折射率系数可归因于两步吸收产生的自由载流子散射效应。当激发光强增大时,在锗层厚度为6 nm的多层膜中同时存在两步吸收过程和饱和吸收过程。两种非线性光学吸收过程之间的竞争是样品呈现不同非线性光学特性的主要原因。Nanocrystalline Ge（ nc-Ge） / Si Nxmultilayers were fabricated by plasma enhanced chemical vapor deposition technique and post-thermal annealing method. The microstructure was characterized through Raman spectroscopy,and the calculated crystallinity was higher than 46%. The optical absorption spectra reveal that the band gap enlarges as the grain size of nc-Ge decreases. The nonlinear optical properties of nc-Ge / Si Nxmultilayers were investigated through Z-scan technique by using a mode-locking laser with 25 ps pulse duration at 1 064 nm as the pump laser. The measured nonlinear refractive coefficient was about 10^（-10）cm^2/ W. It is interesting to found the nonlinear optical refraction changes from the self-defocusing to self-focusing with the increasing of the grain size of nc-Ge,and the negative nonlinear refractive coefficient can be attributed to the free carries dispersion generated by tow-step absorption process. Moreover,two-step absorption and saturation absorption process coexist in the multilayers with 6 nm Ge layer as the pump intensity increases. The different optical nonlinearities are mainly originated from the competition between the two nonlinear absorption processes.

关 键 词：nc-Ge/SiNx多层膜 饱和吸收 两步吸收过程 自由载流子散射 

分 类 号：O437[机械工程—光学工程] O484.41[理学—光学]