共查询到19条相似文献,搜索用时 953 毫秒
1.
2.
3.
采用H-S波前传感器对于非稳腔进行了实验调腔技术研究,指出了正支共焦腔调腔的原则,以输出光束近场强度和相位分布这一双重依据作为谐振腔是否调好的标准。进行非稳腔调腔时,首先应当保证整个光路共光轴使输出强度分布均匀,但此时光束中可能还包含离焦等高阶像差,因此在腔外用Hartmann-Shack波前传感器进行光束相位测量,得到了35阶像差Zernike系数、波面PV和RMS值,进一步计算得到远场分布和环围能量曲线等。从而可以全面了解输出光束质量,并能有针对性地对光腔进行调整,从而达到较理想的光腔调整共轴状态。 相似文献
4.
高斯光束通过非线性介质层的限幅效应 总被引:2,自引:0,他引:2
本文用数值分析的方法研究了两维高斯光束通过一定厚度的非线性折射介质后在线性空间传播的状态,分析了光束的近场和远场横向强度分布及通过一定孔径光阑的功率.结果表明,在考虑到光束经过非线性介质时,相位与横向分布都会发生变化后,仅在非线性折射效应作用下,在远场就存在限幅效应.在一定的强度范围之内,近场也存在限幅利用的可能性. 相似文献
5.
6.
7.
8.
9.
10.
11.
12.
P. Verma T. Ichimura T. Yano Y. Saito S. Kawata 《Laser \u0026amp; Photonics Reviews》2010,4(4):548-561
The spatial resolution in optical imaging is restricted by so‐called diffraction limit, which prevents it to be better than about half of the wavelength of the probing light. Tip‐enhanced Raman spectroscopy (TERS), which is based on the SPP‐induced plasmonic enhancement and confinement of light near a metallic nanostructure, can however, overcome this barrier and produce optical images far beyond the diffraction limit. Here in this article, the basic phenomenon involved in TERS is reviewed, and the high spatial resolution achieved in optical imaging through this technique is discussed. Further, it is shown that when TERS is combined with some other physical phenomena, the spatial resolution can be dramatically improved. Particularly, by including tip‐applied extremely localized pressure in TERS process, it has been demonstrated that a spatial resolution as high as 4 nm could be achieved. 相似文献
13.
Based on the research in Ref. [5][Materials Science and Engineering, 1989; A122: 57 63], an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency f are obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM (Scanning Electron Acoustic Microscopy) signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2α (α is the radius of the focused electron beam). Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally. 相似文献
14.
15.
基于时空滤波理论, 采用相干函数、功率响应函数、扩展分布函数、双频函数四个系统函数较波导不变量更全面地描述了低频声场的相干结构. 理论分析、仿真研究和海试数据处理都验证了低频声场存在稳定的干涉结构, 当目标由远及近、又由近及远做匀速直线运动时, 相干函数(LOFAR图)的干涉结构为一簇类双曲线; 功率响应函数的干涉图表征了简正波群时延的差分, 体现了其频散特性; 扩展分布函数能反映LOFAR图上干涉条纹的斜率大小; 而双频函数能体现相慢度的差分. 各个系统函数均能特别突出干涉结构的某方面的特征, 各有特色. 相似文献
16.
17.
Kyoung‐Duck Park Yong Hwan Kim Jin‐Ho Park Jung Su Park Hong Seok Lee Sang‐Youp Yim Young Hee Lee Mun Seok Jeong 《Journal of Raman spectroscopy : JRS》2012,43(12):1931-1934
We have constructed an ultraviolet (UV)‐apertureless near‐field scanning optical microscope‐Raman spectroscopy system by using an aluminum tip for the simultaneous measurement of topography and Raman scattering of nanomaterials with high spatial resolution. The topography, Rayleigh scattering image, and tip‐enhanced Raman scattering image of the carbon nanotube film showed that a spatial resolution of around 19 nm was achieved. This spatial resolution of UV‐Raman mapping image exceeds that of previous approaches, which have several hundred nanometers of spatial resolution. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
18.
We propose an optical imaging system, in which both illumination and collection are done in far field, that presents a power of resolution better than one-tenth of the wavelength. This is achieved by depositing the sample on a periodically nanostructured substrate illuminated under various angles of incidence. The superresolution is due to the high spatial frequencies of the field illuminating the sample and to the use of an inversion algorithm for reconstructing the map of relative permittivity from the diffracted far field. Thus, we are able to obtain wide-field images with near-field resolution without scanning a probe in the vicinity of the sample. 相似文献
19.
近场光学是指当光探测器及探测器-样品间距均小于辐射波长条件下的光学现象.利用近场光学扫描显微镜和近场光谱仪,不但能够以突破衍射极限的超高分辨率在纳米尺度实现光学成像,而且还可获得纳米微区的光谱信息.文章介绍近场光学的原理及其在凝聚态物理领域中的应用与进展,并给出了我们的初步结果 相似文献