摘要
对比分析了单、双光束偏振倍频技术在确定各向同性纳米金膜二阶非线性效应方面的优劣势。研究结果表明基于射频磁溅射方法制备的100 nm金膜样品具有面内各向同性特征。在单光束手性实验装置中,当采用p线偏振起始光并探测(p±s)偏振倍频光时,纳米金膜的实验拟合展开系数不唯一,改以s或(p+s)偏振为起始光时,相应实验展开系数唯一;而对于双光束技术相关展开系数的唯一性则不受起始光偏振条件的限制。单光束技术仅能测定纳米金表面结构对称性破缺产生的有效表面电偶极贡献,双光束技术则能实现其内部多极贡献(磁偶极和电四极效应)的完全分离;由两实验装置确定的非零独立二阶非线性极化率张量元在数值和位相上接近,当仅考虑纳米金的表面电偶极效应时,双光束技术测得的张量元可实现其质量自检验。在表征纳米金膜的非线性效应方面,双光束技术更具优势,且这一结论适用于具有高对称结构的薄膜/块体材料。
The advantages and disadvantages of one- and two-beam polarization second-harmonic generation（SHG） techniques are reported for the determination of the second-order nonlinear effect of isotropic nanogold film. The results indicate that 100 nm gold film fabricated by radio frequency magnetron sputtering on glass substrates is isotropic in the plane of the substrate. Expansion coefficients for nanogold film in one-beam chiral experimental setup are not unique for the measurement of p-polarized initial beam and p±s-polarized secondharmonic beam, and they are unique for s- or（p＋s）-polarized initial beam; but the uniqueness of expansion coefficients in two-beam geometry is without the limitation of the initial beam polarizations. The obtained results also show that one-beam technique only determines these contributions related to the effective electric-dipolar effect arising from the broken symmetry at the surface of an isotropic gold film, but bulk multipolar（magnetic dipole and electric quadruple effects） contributions of nanogold can be completely separated from its surface second-order nonlinear optical response in the two-beam setup, and all the non-vanishing tensor components obtained in both experimental geometries are very close in value and phase, and when only considering the surface electric-dipole effect of nanogold, the quality of its tensor components can also be checked by two-beam technique. So two-beam technique has more advantages than one-beam technique in the characterization of the nonlinearity of nanogold,and this conclusion can be applied to thin films /bulk materials with high structural symmetry.
出处
《光学学报》
EI
CAS
CSCD
北大核心
2015年第12期211-219,共9页
Acta Optica Sinica
基金
国家自然科学基金(11204057)
教育部新世纪优秀人才支持计划基金(NCET-11-0929)
海南省自然科学基金(112003)
海南大学校青年基金(qnjj1237)
关键词
非线性光学
倍频
电偶极和多极效应
纳米金膜
单、双光束技术
展开系数
nonlinear optics
second-harmonic generation
electric-dipolar and multipolar effects
nanogold film
one-and two-beam techniques
expansion coefficients
