具有准单级聚焦特性的梯形波带片（英）

为改进用于X射线聚焦的二值化Gabor波带片目前所存在的结构复杂、不利于加工制作的问题,在不改变梯形透过率函数的前提下,通过将传统的梯形孔基元变为平行四边形基元应用于波带片的设计之中,提出了一种聚焦效率更高的具有准单级聚焦特性的波带片。理论推导显示,该波带片除了像Fresnel波带片一样能够消除偶数级的焦点外,还可以消除3q级（q为整数）的焦点,1/m4（m为焦点级数）的效率衰减系数也使得高级衍射得到了很好的抑制。MATLAB数值模拟的结果证明,该波带片的特性不仅满足以上推论,还具有比Fresnel波带片和环带扇形基元阵列波带片更低的背景噪声,可以看作是一种准单级聚焦的新型波带片。此外,在同一波带内,这种基于平行四边形基元孔的波带片设计的透光区始终保持各处的径向宽度为该波带的一半,且扇区结构简单一致,能够降低不少加工难度,易于推广应用。     

具有准单级聚焦特性的梯形波带片（英）

为改进用于X射线聚焦的二值化Gabor波带片目前所存在的结构复杂、不利于加工制作的问题,在不改变梯形透过率函数的前提下,通过将传统的梯形孔基元变为平行四边形基元应用于波带片的设计之中,提出了一种聚焦效率更高的具有准单级聚焦特性的波带片。理论推导显示,该波带片除了像Fresnel波带片一样能够消除偶数级的焦点外,还可以消除3q级（q为整数）的焦点,1/m4（m为焦点级数）的效率衰减系数也使得高级衍射得到了很好的抑制。MATLAB数值模拟的结果证明,该波带片的特性不仅满足以上推论,还具有比Fresnel波带片和环带扇形基元阵列波带片更低的背景噪声,可以看作是一种准单级聚焦的新型波带片。此外,在同一波带内,这种基于平行四边形基元孔的波带片设计的透光区始终保持各处的径向宽度为该波带的一半,且扇区结构简单一致,能够降低不少加工难度,易于推广应用。     

准随机点阵二值化Gabor波带片聚焦特性的数值计算

 Fresnel波带片有多个焦点,作为单色器波长选择元件使用时会受到高级衍射的影响。而Gabor波带片只有一个焦点,有更好的聚焦特性,但制作难度较大,准随机点阵二值化Gabor波带片概念的提出则解决了这个问题。介绍了准随机点阵二值化Gabor波带片的设计,并利用优化的程序分别对Fresnel波带片和准随机点阵二值化Gabor波带片的聚焦特性进行了模拟计算,通过对计算结果进行分析比较,发现准随机点阵二值化Gabor波带片具有抑制高阶衍射的特性。     

准随机点阵二值化Gabor波带片聚焦特性的数值计算

Fresnel波带片有多个焦点,作为单色器波长选择元件使用时会受到高级衍射的影响。而Gabor波带片只有一个焦点,有更好的聚焦特性,但制作难度较大,准随机点阵二值化Gabor波带片概念的提出则解决了这个问题。介绍了准随机点阵二值化Gabor波带片的设计,并利用优化的程序分别对Fresnel波带片和准随机点阵二值化Gabor波带片的聚焦特性进行了模拟计算,通过对计算结果进行分析比较,发现准随机点阵二值化Gabor波带片具有抑制高阶衍射的特性。     

Square-shaped beam generated by phase shifted bounded square zone plate

A novel diffractive element is presented which is made through lateral phase shifted square zone plate bounded along horizontal and vertical axes via two perpendicular rectangle windows, respectively. We demonstrate that under a given condition the element is able to produce a square light beam at the focal plane. We have also elaborated that the produced square beam can be simply manipulated by an appropriate combination of the phase shifting parameter and bounded width. Experimental works verify the simulation results.     

Comparison of subwavelength focusing properties of diffraction and Fresnel zone plate plasmonic planar lenses

The subwavelength focusing properties of diffractive plasmonic planar lenses (DPLs) and Fresnel zone plate plasmonic planar lenses (FZPs) have been compared in this paper. To that end, we use the same lens material, incident wavelength, thickness and focal length for comparison. Both DPLs and FZPs consist of central circular slits surrounded by transparent and opaque zones and can get clear focusing performances. By using the rigorous electromagnetic numerical method, the fields in the focal region are analyzed in detail, and our results demonstrate that FZP can generate higher transmission efficiency, and higher peak field intensity at the focal plane. Focusing polarization properties of the lens illuminated by linearly polarized state, are calculated and analyzed also. The numerical results show that both the DPL and the FZP produce asymmetrical focal spot distributions with a low f-number. To the FZP, the full-width at half-maximum (FWHM) varies from 256 nm (along y-axis) to 516 nm(along x-axis) and to the DPL, the FWHM varies from 256 nm(along y-axis) to 580 nm(along x-axis), respectively. But for a high f-number, the asymmetrical performance of the focal spot will be reduced due to complicated electromagnetical field interferences and micro waveguide effect. Otherwise, the DPL can get a higher depolarization effect than the FZP does.     

Full-transparent zone plates for THz focusing

A full-transparent zone plate(FTZP), which can reuse the wave blocked in the focusing of the Fresnel zone plate(FZP), is proposed to improve the efficiency of terahertz(THz) focusing without aberration. We find that the substrate thickness of the FTZP has a great influence on the focusing intensity, which results from the Fabry–Perot effect. The focusing efficiency of FTZPs could be about twice as high as that of FZPs, but the widths of both focus spots are comparable with the wavelength. The experimental results are in good agreement with the simulation.     

Experimental demonstration of near-field focusing of a phase micro-Fresnel zone plate (FZP) under linearly polarized illumination

A high numerical aperture binary phase micro-Fresnel zone plate (FZP) is designed and fabricated on a glass substrate by using a focused ion beam technique. Focusing characteristics of the phase micro-FZP are measured by a near-field scanning optical microscope using linearly polarized light as an illumination source. It is found that an asymmetric spot with subwavelength beam width and elongated depth of focus can be obtained from the phase micro-FZP. Furthermore, the measurement is shown to be consistent with the calculation result. Further, the tolerance in fabrication errors like tilt of side walls on focusing is discussed with numerical simulations.     

Diffractive performance of square Fresnel zone plates

We analyze the optical behavior of square Fresnel zones plates. A theoretical analysis and numerical simulations based on the Rayleigh-Sommerfeld approach have been developed analyzing properties such as the depth of focus and the intensity of the focus in terms of the number of zones. In addition, an experimental verification has been performed using a Spatial Light Modulator to implement the designed square Fresnel zones plates.     

方形激光斑聚焦器理论及实验

本文从理论上详细研究一种可将激光会聚为方形光斑的光学系统,并与另一种同类装置的理论计算及实验结论进行对照.     

Beyond-limit light focusing in the intermediate zone

We experimentally verify that a new nanolens of a designed plasmonic aperture can focus visible light to a single line with its width smaller than the limit of half the wavelength in the intermediate zone. The experimental measurement indicates that while the near field plays a role to increase the spot size in the near zone, it is negligible at the beyond-limit focused region; i.e., the focused light is dominated by the radiative fields. The image taken by the optical microscope shows that the fields focused have propagated to the far zone. Besides being of academic interest, the nanolens capable in achieving a lower diffraction limit in the intermediate zone is important for application possibilities.     

Fourier-transform hologram by zone plate

A simple technique is described and demonstrated as well that Fourier-transform holograms can be made with a zone plate.     

Fresnel波带板编码成像技术

 介绍了Fresnel波带板编码成像原理,并设计出高空间分辨率的Fresnel波带板编码相机,用双孔可见光源对编码相机的成像进行了实验研究,表明该编码相机可以真实地还原源区的空间大小和形状。     

影响连续相位板聚焦性能的主要因素

为提高惯性约束聚变系统中聚焦光斑的能量集中度,分析了在应用过程中影响连续相位板性能的主要误差来源,并建立了相应的数学模型。通过分析得出存在误差时远场焦斑的能量集中度和均方根值,且口径误差、对准误差、振幅畸变误差对连续相位板的聚焦性能影响很小,波前畸变影响能量集中度的权重最大。进一步分析可知:当畸变波前相关长度与连续相位板的最小空间周期（10 mm左右）相当时,畸变波前极大地影响激光的聚焦性能,提高惯性约束聚变系统中畸变波前的相关长度是提高聚焦光斑的能量集中度的有效方法。     

Factors affecting focusing performance of continnous phase plate concentration

为提高惯性约束聚变系统中聚焦光斑的能量集中度,分析了在应用过程中影响连续相位板性能的主要误差来源,并建立了相应的数学模型.通过分析得出存在误差时远场焦斑的能量集中度和均方根值,且口径误差、对准误差、振幅畸变误差对连续相位板的聚焦性能影响很小,波前畸变影响能量集中度的权重最大.进一步分析可知:当畸变波前相关长度与连续相位板的最小空间周期(10 mm左右)相当时,畸变波前极大地影响激光的聚焦性能,提高惯性约束聚变系统中畸变波前的相关长度是提高聚焦光斑的能量集中度的有效方法.