基于氧化石墨烯/金纳米棒复合基底的SERS性能分析

以具有拉曼散射表面活性的金纳米棒(AuNRs)与氧化石墨烯(GO)溶液混合。通过控制AuNRs的尺寸、用量,抽滤制得氧化石墨烯/金纳米棒(GO/AuNRs)复合薄膜。利用紫外-可见分光光度计、透射电子显微镜(TEM)对制得的GO/AuNRs进行了表征和分析,并且采用拉曼光谱研究GO/AuNRs基底的表面增强散射(SERS)效应。结果表明,GO/AuNRs基底的SERS性能能够对芳香烃类大分子物质起到信号增强的作用。以罗丹明B(RhB)为探针分子验证其拉曼增强效应,在超微量浓度时依然具有较强的拉曼信号,增强因子达到2250。     

Optical super-resolution effect induced by nonlinear characteristics of graphene oxide films

In this work, we focus on the optical super-resolution effect induced by strong nonlinear saturation absorption (NSA) of graphene oxide (GO) membranes. The third-order optical nonlinearities are characterized by the canonical Z-scan technique under femtosecond laser (wavelength:800 nm, pulse width:100 fs) excitation. Through controlling the applied femtosecond laser energy, NSA of the GO films can be tuned continuously. The GO film is placed at the focal plane as a unique amplitude filter to improve the resolution of the focused field. A multi-layer system model is proposed to present the generation of a deep sub-wavelength spot associated with the nonlinearity of GO films. Moreover, the parameter conditions to achieve the best resolution (~l/6) are determined entirely. The demonstrated results here are useful for high density optical recoding and storage, nanolithography, and super-resolution optical imaging.     

紧聚焦的角向偏振艾里光束产生超分辨光针

为了研究角向偏振艾里光束的紧聚焦特性,采用理查德-沃夫矢量衍射理论分析优化了艾里光束的指数衰减因子、主环半径与比例因子对其入射光场分布的影响;分别研究了角向偏振艾里光束聚焦场分布与涡旋滤波器调制的角向偏振艾里光束的聚焦场分布,得到亚波长的角向中空场分布与亮场分布,实验结果与理论模拟基本一致.进一步利用粒子群算法设计多环...     

Super-resolution longitudinally polarized light needle achieved by tightly focusing radially polarized beams

Based on the vector diffraction theory, a super-resolution longitudinally polarized optical needle with ultra-long depth of focus (DOF) is generated by tightly focusing a radially polarized beam that is modulated by a self-designed ternary hybrid (phase/amplitude) filter (THF). Both the phase and the amplitude patterns of THF are judiciously optimized by the versatile particle swarm optimization (PSO) searching algorithm. For the focusing configuration with a combination of a high numerical aperture (NA) and the optimized sine-shaped THFs, an optical needle with the full width at half maximum (FWHM) of 0.414λ and the DOF of 7.58λ is accessed, which corresponds to an aspect ratio of 18.3. The demonstrated longitudinally polarized super-resolution light needle with high aspect ratio opens up broad applications in high-density optical data storage, nano-photolithography, super-resolution imaging and high-efficiency particle trapping. This work has been supported by the National Natural Science Foundation of China (Nos.61575139, 61605136, 51602213 and 11604236), and the Youth Foundation of the Taiyuan University of Technology (No.2015QN066). This paper was recommended by the 9th International Conference on Information Optics and Photonics (CIOP 2017). E-mail:niezhongquan@tyut.edu.cn