纳米孔径激光器出射孔径设计

采用三维时域有限差分（FDTD）方法计算和比较了不同形状和尺寸的纳米孔径半导体激光器的近场分布特性，结果表明采用C形孔径设计可使纳米孔径激光器的输出光强最大值比方孔和圆孔提高了3－4个数量级，通光效率也会有显著提高而聚焦光斑尺寸基本不变。并提出C形孔在孔径尺寸为1／3波长左右时输出光场分布最优。纳米孔径激光器可用于超高密度近场光存储、近场光学超衍射分辨成像、纳米光刻等。     

阶梯型纳米孔径的近场光学局域增强特性研究

提出一种高分辨力与高通光效率兼备的阶梯型纳米孔径设计方法 ,孔径的尺寸从膜层的入射表面向出射表面呈阶梯型逐渐减小 ,直到在膜层的出射表面形成一个亚波长的小孔。采用三维时域有限差分 (FDTD)方法对方形阶梯型纳米孔径及三角形阶梯型纳米孔径进行了数值模拟计算。结果表明 ,由于近场光学很强的局域场增强效应 ,其通光效率与输出光强极大值在具有相同近场光斑尺寸情况下 ,较普通的非阶梯型纳米孔径提高了两个数量级 ,甚至更高 ,有效地提高了输出光功率。采用四台阶三角形阶梯型纳米孔径 ,当光斑半峰全宽为 97nm× 74nm时 ,出射光强极大值达到 10 4 9.76 ,较入射光增强了 10 0 0倍 ,而通光效率大于 1,达到 1.6 7。这种阶梯型纳米孔径可以直接作为纳米孔径激光器的出射孔径提高其输出光功率 ,也可以作为独立的光学屏对入射光进行整形得到具有高输出功率的亚波长尺度光源 ,在纳米尺度光学成像、光谱探测、数据存储、光刻、光学操作等近场光学应用领域具有潜在的应用前景。     

近场光学虚拟光探针的数值分析

虚拟光探针是基于近场光学隐失场干涉原理产生的一种非实体探针，可以应用于近场光学超高密度存储、纳米光刻、近场光学成像、光谱探测、纳米样品的近场光学操作等领域。本研究采用三维时间域有限差分（FDTD）方法对近场光学虚拟光探针的光场分布特性进行了数值模拟计算和比较，分析了孔的形状、大小及偏振态等因素对虚拟光探针光场分布的影响，研究结果表明虚拟光探针的通光效率较普通的纳米孔径光纤探针提高10^2-10^4倍；其光场分布的中间峰的半峰全宽（即虚拟光探针的尺寸）在一定距离范围内基本保持不变，从而可以解决近场光学系统中纳米间距控制的难题，避免光学头与介质的磁撞。优化虚拟光探针的设计参量能有效的抑制虚拟光探针中的旁瓣。文章还给出了应用虚拟探针实现高密度光存储的原理方案。     

二元环形孔径全空间轴线上的衍射光强分布

运用Rayleigh-Sommerfeld衍射积分,详细推导了二元环形孔径全空间在轴光强分布公式.由于未作明显的近似,所得公式对衍射距离大于数倍入射波长的衍射空间都是有效的.计算并分析了这种孔径轴线上的光强分布情况.结果显示,它的最大调制深度是入射光强的16倍,比圆形孔径或环形孔径大4倍,近场的光学层析能力比远场的强.在很近场区,二元环形孔径的在轴光强分布对孔径结构比较敏感,这些特性使这种孔径在光子学和光纤光学的应用方面具有潜在的价值.     

细菌视紫红质近场光存储特性的研究

结合近场光学显微镜，利用菌紫质M态和基态之间的跃迁，对BR—D96N样品作了静态近场光存储特性的研究。结果表明，近场区域内细菌视紫外质在光激发前后对红光的吸收有较大差别，而且激发后无光照时会缓慢弛豫到激发前的状态，具有光致变色特性和热弛豫特性，可望作为近场光存储材料和微光学信息处理器件材料。     

微小孔径激光器的研制与近场测试

介绍了一种用于高密度近场存储领域的新型微小孔径激光器(VSAL)。为了解决由腔面金属膜造成的激光器PN结短路的问题,在激光器中引入了窗口隔离区,不仅降低了器件制备的难度,而且也提高了器件的性能和成品率。采用聚焦离子束刻蚀技术成功地制备了输出功率为0 3mW的激光器,利用矩阵方法通过远场测量值估算了激光器的近场分布。     

基于纳米孔径激光器的近场光存储的最新发展

近几年发展起来的近场光学原理和方法为实现超高密度光学数据存储开辟了新的技术途径。基于近扬光学方法的最小信息记录单元尺寸突破了经典光学分辨率的衍射极限 ,理论存储密度高达 1 0 0 0Gb/平方英寸 ,受到了研究人员和工业界的广泛关注。着重介绍了用于近场光学存储的纳米孔径激光器的原理、结构、优点 ,对它的实现方法和发展状况作了详细的阐述 ,并对其在近场光存储领域未来的发展趋势进行了展望     

近场光存储及其研究进展

本文从近场光学的超分辨原理出发详细介绍和分析了孔径探针型近场光存储技术、SIL透镜近场光存储技术和近场超分辨结构光盘存储技术等的基本原理、研究现状以及它们的优缺点及存在的问题     

近场光存储及其研究进展

本文从近场光学的超分辨原理出发详细介绍和分析了孔径探针型近场光存储技术，SIL透镜近场光存储技术和近场超分辨结构光盘存储技术等的基本原理、研究现状以及它们的优缺点及存在的问题。     

用时阈有限差分方法研究光纤微探针近场分布特性

采用三维时间域有限差分（FDTD）方法研究了扫描近场光学显微镜中光纤微探针的近场分布特性,研究结果表明,锥形裸光纤探针的近场光中,以从探针锥变区侧面泄露的光即传播场为主,当在探针的侧面镀上一层金属膜对于从侧面泄露的光具有较好屏蔽效果,因而比裸光纤探针具有更好的空间束缚能力,无论是裸光纤探针还是金属膜探针,入射偏振光从针尖出射手发生了退极化现象,近场分布中产生与入射光偏振方向垂直的其它两个电场分量,而且金属膜探针的退极化分量对近场分布的影响比裸探针显著得多,如果在近场成像中接收退极化分量而不是总场则可以提高近场成像的对比度,还详细地分析了微探针的近场分布特征与退极化之间的关系。     

Theoretical Analyses on the Resolution of Collection Mode Scanning Near-Field Optical Microscopy

Numerical simulations have been carried out in the framework of waveguide theory to model collection mode scanning near-field optical microscopy (SNOM). The theoretical model includes the optical fiber end and describes the metal coated aperture on the probe tip. The developed formalism goes beyond the existing Bethe-Bouwkamp theories for electromagnetic transmission of subwavelength apertures. The finite coating and optical fiber end are now taken into account. The new features enable us to simulate the near-field probes that are widely used in the collection mode SNOM. The emphases of the numerical analyses have been mainly on the resolution mechanism of the microscopy. Influence on the resolution from important parameters of the probe tips, such as the size of the apertures and the probe-sample distance, is extensively studied. The resolution dependence has been analyzed in the light of the near-field coupling efficiency of the probe tip. An optimum tip size has been found which is balanced between the significant signal transmission and the resolution of the device.     

Optical transmission enhancement by a sub-wavelength film lens

A new sub-wavelength metallic film lens configuration is proposed, which is embedded in a thin ideal metal film, and its near field optical properties are investigated by finite-difference time-domain (FDTD)method. It is found that the optical transmission is greatly enhanced, and the spot size can be reduced by the sub-wavelength metallic film lens in comparison with the bare aperture. This kind of lens is expected to have practical applications in the very small aperture laser (VSAL), a promising nanosource for near-field optical storage and lithography.     

SETUP AND APPLICATION OF SCANNING NEAR-FIELD OPTICAL MICROSCOPY

The research on the setup and application of scanning near-field optical microscopy (SNOM) performed in our laboratory is reviewed in this report. We have constructed a versatile low temperature scanning near-field optical microscope with the capability of near-field imaging and spectroscopy, operating at liquid nitrogen temperature. A special designed coaxial double lens was used to introduce the illumination beam through a 200μm fiber; the detected optical signal was transmitted via a fiber tip to an avalanche photon detector. The performance test shows the stability of the new design. The shear force image and optical image of a standard sample are shown. A system of SNOM working at room temperature and atmosphere was used to characterize semiconductors and bio-molecular samples. It revealed the unique features of semiconductor microdisks in the near-field that is significantly different from that of far-field. The effects of different geographic microstructures on the near-field light distribution of InGaP, GaN, and InGaN multi-quantum-well microdisk were observed.     

Dual mode near-field scanning optical microscopy for near-field imaging of surface plasmon polariton

In this paper, we theoretically and experimentally demonstrate that metal coated apertured probes are efficient near-field probes on surfaces with high reflectivity for the scattering as well as for the collection mode near-field scanning optical microscopy (NSOM). We show that a blunt apertured metal coated tip is very effective in suppressing image dipoles which affect strongly the signals scattered from frequently used sharp metal tips or gold nanoparticle attached probes. By using a simultaneous collection and scattering mode (dual mode) NSOM we measure the near-field images of surface plasmon polariton (SPP) launched from a slit. The collection mode measures propagating SPP along lateral distance in a long scan range with high signal-to-noise ratio, and the scattering mode measures the polarization resolved near-field of SPP. Comparisons of the measured data obtained in the dual mode enable to easily characterize SPP and to separate the measured near-field into the propagating SPP and the directly transmitted light.     

A virtual optical probe based on evanescent wave interference

A virtual probe is a novel immaterial tip based on the near-field evanescent wave interference and small aperture diffraction, which can be used in near-field high-density optical data storage, nano-lithography, near-field optical imaging and spectral detection, near-field optical manipulation of nano-scale specimen, etc. In this paper, the formation mechanism of the virtual probe is analysed, the evanescent wave interference discussed theoretically, and the sidelobe suppression by small aperture is simulated by the three-dimensional finite-difference time-domain method. The simulation results of the optical distribution of the near-field virtual probe reveal that the transmission efficiency of the virtual probe is 10²－10⁴ times higher than that of the nano-aperture metal-coated fibre probe widely used in near-field optical systems. The full width at half maximum of the peak, in other words, the size of virtual probe, is constant whatever the distance in a certain range so that the critical nano-separation control in the near-field system can be relaxed. We give an example of the application of the virtual probe in ultrahigh-density optical data storage.     

阿基米德螺旋微纳结构中的表面等离激元聚焦

研究光在微纳结构中的分布与传播, 实现在纳米范围内操纵光子, 对于微型光学芯片的设计有着重要意义. 本文利用聚焦离子束刻蚀方法, 在基底为石英玻璃的150 nm厚金膜上刻制了不同参数的阿基米德螺旋微纳狭缝结构, 通过改变入射光波长、手性、及螺旋结构手性和螺距等方式, 在理论和实验上系统地研究了阿基米德螺旋微纳结构中的表面等离激元聚焦性质. 我们发现, 除了入射激光偏振态、螺旋结构手性之外, 结构螺距与表面等离激元波长的比值也可以用来控制结构表面电场分布, 进而在结构中心形成0阶、1阶乃至更高阶符合隐失贝塞尔函数的涡旋电场. 通过相位分析, 我们对涡旋电场的成因进行了解释. 并利用有限时域差分的模拟方法计算了不同螺距时, 结构中形成的电场及相应空间相位分布. 最后利用扫描近场光学显微镜, 观测结构中不同的光场分布, 在结构中心得到了亚波长的聚焦光斑及符合不同阶贝塞尔函数的涡旋形表面等离激元聚焦环.