Dispersion effect in optical microscopy systems with a supersphere solid immersion lens

This paper studies the dispersion effect of the supersphere solid immersion lens (SIL) on a near field optical microscopy system by using the vector diffraction theory. Results show that when a real non-monochromatic beam illuminates a supersphere SIL microscopy, the dispersion effect of the SIL has an important influence on the image quality. As the wavelength bandwidth of the non-monochromatic beam increases, the size of the focused spot increases and its intensity decreases in near-field microscopy systems with a supersphere SIL.     

固体浸没透镜用于飞秒三维光存储研究

为进一步提高光存储密度，利用固体侵没透镜（SIL）与数值孔径为0.55的长工作距离物镜对飞秒激光脉冲进行聚焦，完成了PMMA及石英介质上的存储实验,并对聚焦物镜焦点与SIL底面离焦时的介质内焦点位置和系统的数值孔径进行了模拟。实验结果表明：当聚焦物镜焦点与SIL底面适当离焦时，实际聚焦在介质内的焦点深度不断加深，且系统的有效数值孔径不断增大。利用这一结果，在距PMMA表面20μm的地方得到了点间距1μm，层间距2.5μm的6层空间点阵；在距石英介质表面15μm的地方获得了点间距为0.6μm，层间距为2.5μm的5层空间点阵，其存储密度可达1.1×1012bits/cm3。     

Optimizing the optical field distribution of solid immersion lens system by a continuous phase filter

In solid immersion lens (SIL) microscopy systems with high numerical aperture (NA), there always exists the aberration produced by Fresnel effects at the interface between SIL and the sample. This aberration may cause the degradation of the image of sample. We design a continuous phase filter and optimize the optical field distribution of SIL system. The numerical results show that when the continuous phase filter is used, the field distribution of SIL system can be optimized, and the focal depth and intensity of transmitted light can be increased. At the same time, the intensity of side-lobe and the resolution are kept almost unchanged.     

Three-dimensional optical data storage using a solid immersion lens to focus a femtosecond laser pulse

A solid immersion lens (SIL) has been applied to the writing and reading of three-dimensional optical datastorage in transparent materials. Using a SIL with n=1.516 to focus a 150-fs, 800-nm Ti:sapphire laser,the 5-layer reading and writing of data are achieved in fused silica and polyethylene methacrylate at adensity of 1.1× 1012b/cm3. Some advantages of the employment of SIL have been discussed.     

The validity of high-pass angular spectrum filter in solid immersion lens system

应用矢量方法计算了具有高通角谱滤波器的固体浸没透镜（SIL）系统的焦场分布。数值结果显示，对于径向（角向）偏振输入光，高通角谱滤波器可以减小SIL系统的光斑（暗斑）大小。然而，对于线性偏振输入光，简单的高通角谱滤波器不能够优化SIL系统的光场分布，也不能够改进系统的光存储密度。     

Experimental research on high density data storage using solid immersion lens

We have set up a solid immersion lens (SIL) near-field static recording system for demonstrating preliminarily the feasibility of SIL technology in the higher density storage. The experimental result with recording mark size of 240 nm is obtained corresponding to a potential of density of tens of gigabits per square inch. Some factors in the SIL near-field recording are discussed.     

Improving the resolution of a solid immersion lens optical system using a multiphase Fresnel zone plate

We propose a method to improve the resolution of near-field optical system with a solid immersion lens by using a multiphase level Fresnel zone plate. The analyses are based on scalar angular spectrum theory. The results show that the multiphase Fresnel zone plate can not only decrease the spot size but also decrease the sidelobe intensity and enhance greatly the diffractive efficiency compared with annular amplitude filter or binary 2-, 3-, 4-zone phase filter.     

Theoretical study of optical recording with a solid immersion lens illuminated by focused double-ring-shaped radially-polarized beam

Based on the Richards–Wolf vector diffraction theory, the intensity distributions in the recording sample near a solid immersion lens are calculated for two different radially-polarized beams ( and modes). Numerical results show that a double-ring-shaped mode focusing has some excellent features in near-field optical storage, compared with a single-ring-shaped mode focusing. The recording density is markedly improved, the focal depth of the near-field recording system is substantially increased, and a subsurface recording is effectively obtained using the mode focusing.     

固体浸没透镜光存储的信号探测技术

信号探测是固体浸没透镜成为实用存储技术的一个必需的组成部分。对在该项研究中获得的理论和实验成果进行了介绍。总结了针对固体浸没透镜机理的三维矢量理论 ,对影响信号探测的因素 ,例如头盘间距、盘片结构和光的偏振态等进行了讨论。介绍了基于固体浸没透镜光存储中信号探测的新技术和重要的实验结果。     

超半球形固体浸没透镜系统的亚表面显微

应用矢量衍射理论和薄膜光学方法,研究了有禁带存在时超半球形固体浸没透镜(SIL)系统的亚表面显微。模拟计算结果显示,光斑的强度,边瓣强度和光斑大小随禁带厚度发生振荡。光斑的大小和光斑的强度几乎是反相变化的。当禁带材料的折射率与固体浸没透镜(SIL)的折射率相匹配时,光斑的强度较大,分辨率较高。随着离开样品表面的距离的增加,光斑的强度不断减小,光斑的大小和边瓣强度逐渐增加。     

相位光阑对光学系统中焦深的影响

焦深在高密度光盘存储系统中具有十分重要的作用,大焦深可以使调焦伺服系统容易跟踪盘面。采用标量衍射理论和基于德拜近似条件的矢量衍射理论,分别在低数值孔径和高数值孔径两种情况下,系统研究相位光阑对聚焦光学系统的轴向光强分布和焦深的影响。研究结果表明：相位光阑对光学系统的焦深影响很大,高数值孔径系统中,选择适当的相位光阑几何尺寸可以使焦深提高约6倍。     

Evanescent imaging with induced polarization by using a solid immersion lens

Image contrast enhancement, high lateral resolution, and height information are obtained with induced polarization evanescent imaging using a solid immersion lens. Experiments are conducted by imaging features on a patterned Si substrate. Imaging theory is used to predict optimum orientation of high-spatial-frequency samples, and a topographical image is derived from the induced polarization image through a calibration procedure. A numerical aperture of 1.5 is used in the experiment. Height accuracy of +/-2 nm is demonstrated with a known sample.     

Multiple reflection effect inside a hemispherical solid immersion lens

The reflection inside a hemispherical solid immersion lens (h-SIL) is analyzed by using the film-interference optics and the new unique characteristic of the h-SIL is presented. The image theory of SIL microscopy is developed. Numerical results show that the reflection inside the h-SIL, especially for large mismatch in refractive indices between the SIL and the medium, has an important influence on the resolution of SIL surface microscope and the collection efficiency from the emitter. Theoretical and experimental results are compared through three examples, the reflection-mode microscope, the transmission-mode microscope, and the collection of light from the emitters. The present theoretical values are quite consistent with the experimental values in SIL microscopy. It is of interest to note that owing to the interference in the SIL, the resolution and collection efficiency periodically oscillate with the radius of an h-SIL, which mean that the radius of an h-SIL has to be well-controlled to achieve enough high resolution and collection efficiency.     

Fabrication of micrometer-size glass solid immersion lens

A micrometer-size solid immersion lens (μ-SIL) of glass with a super-spherical shape is obtained using a simple preparation procedure. Soda-lime–silica glass particles are melted on a glassy-carbon substrate with a surface of optical grade and cooled to room temperature. The obtained glass particles are transparent and have a super-spherical shape. Their shapes are found to satisfy the conditions of the SIL function for evanescent-field optics. Fine uneven surface textures of an integrated circuit with the depth of about 20 nm are clearly recognized using the prepared μ-SIL, and 1.8 times higher horizontal resolution than without the μ-SILis also attained. It was ensured that the glass μ-SILworks as the evanescent-field optics to visualize the nanometer-scale structure. PACS 42.70.Ce; 42.79.Bh; 68.03.Cd; 68.08.Bc; 68.37.Uv     

Pupil-plane filtering for improved signal detection in an optical data-storage system incorporating a solid immersion lens

A pupil-plane filtering technique is applied to data-signal detection in an optical data-storage system that uses a solid immersion lens (SIL) and a four-layered phase-change recording medium. We have confirmed by numerical calculations and experiment that the technique improves signal contrast and makes the contrast less sensitive to the gap width between the bottom surface of the SIL and the top surface of the recording medium. Light that is incident upon the objective lens that is used with the SIL is linearly polarized, and the full vectorial feature of the light is considered in the calculations.     

Numerical analysis of an annular-aperture solid immersion lens

A physical model of an annular-aperture solid immersion lens (SIL) is proposed, and its attractive features are presented numerically with the finite-difference time-domain method. Placing an appropriate annular aperture in front of the SIL shows that the focal depth can evidently be improved, combining the virtues of the annular-aperture technique and the SIL technique. With this proposed method the rigorous distance control condition in related devices can be relaxed, preventing scratches or collisions between the optical head and the recording medium. Potentially, this technique could have great prospects for applications in optical data recording, lithography, and other applications that depend on immersion media to meet the resolution criteria across the image field.     

Effect of polarization on focal depth in high numerical apertures optical systems

The generalized cylindrical vector beam is just a linear combination of radial and azimuthal polarization. For radially polarized light in the focal plane, there are two electric field components, the radial component and z-component whose magnitude increase with the increase of numerical aperture. By contrast, for azimuthally polarized light in the focal plane, there is only one electrical field component in the azimuthal polarization, it is easy to understand the difference between the two polarization effects. In this paper, we demonstrate how this phenomenon can be harnessed to make a properly selected polarization component to achieve high focal depth in high numerical aperture systems. Numerical simulations show that the evolution of the focal shape is very considerable by changing polarization rotation angle of the generalized cylindrical vector beam. And some interesting focal spots and focal split may occur. And if the ratio of radial and azimuthal polarization is set properly by changing the polarization rotation angle, a largest focal depth is achieved. The tunable range of the focal depth is very considerable. The ratio of radial and azimuthal polarization is different in different NA optical system for obtaining the largest focal depth. We will denote a technique of polarization-assisted high focal depth in high numerical aperture systems.     

Focus depth characteristics of lenses with long focal depth designed by a focal depth function

The validity of a focal length function is investigated in designing optical element with long focal depth and high lateral resolution. The designed lenses with different starting focal length are studied. Two focusing performance measures, focal depth and lateral resolution, are presented. Comparing with the conventional lens and optical element designed by other focal length function, numerical results of the designed optics element indicate that the long focal depth and high lateral resolution are achieved. The validity of the focal length function is confirmed. Meanwhile, the designed optical element is similar with the lens with spherical aberration. It means that one can easily implement long focal depth by applying appropriate phase modulation to a lens with spherical aberration.     

Near-field radiation from a ridge waveguide transducer in the vicinity of a solid immersion lens

A near-field optical system is investigated to improve the transmission efficiency of near-field transducers. A ridge waveguide is placed adjacent to a solid immersion lens (SIL) but separated by a low-index dielectric layer. The incident electric field near the focus of the SIL is determined by the Richards-Wolf vector field equations. The finite element method is used to solve Maxwell's equations. A spot size of 31 nm is obtained. The maximum value of the absorbed optical power density in the recording medium is 7.51 x 10(-4) mW/nm3 for a 100 mW input power.