Phase zone photon sieve

A novel diffractive optical element, named phase zone photon sieve (PZPS), is presented. There are three kinds of phase plates in PZPSs: PZPS1, PZPS2, and PZPS3. Each of the PZPSs has its own structure and is made on quartz substrate by etching. The three PZPSs have stronger diffraction peak intensity than a photon sieve (PS) when the margin pinhole and zone line width are kept the same. The PZPS3 can produce a smaller central diffractive spot than the ordinary PS with the same number of zones on the Fresnel zone plate. We have given the design method for and the simulation of PZPS and PS. PZPS has potential applications in optical maskless lithography.     

卢卡斯光子筛的聚焦特性研究

介绍了一种基于卢卡斯数编码设计的轴上四焦点光子筛,其各焦距分布与黄金分割比密切相关.实验上利用相移数字全息验证了设计器件具有轴上四焦点聚焦特性,测量结果表明:轴向焦距和横向焦斑光强分布与理论设计值一致.该振幅型光子筛具有体积小、重量轻、易加工等优点,可应用于X波段显微和生物细胞阵列成像等领域.     

准相位型光子筛设计

提出了一种准相位型光子筛。该准相位型光子筛通过改变暗环上小孔直径与带宽的比值,对焦点处的相位分布进行调制,使通过亮环和暗环上小孔的光波在焦点处发生相长干涉,生成聚焦光斑。该准相位型光子筛无需对基底进行特殊处理,即可完成相位型光子筛的制作,降低了加工难度。和普通振幅型光子筛相比,在相同最小加工尺寸的条件下,准相位型光子筛具有较大的数值孔径,可降低聚焦光斑尺寸。并且,和多区光子筛相比,在同样的最小加工尺寸及数值孔径的条件下,准相位型光子筛光斑尺寸及质量均优于对方。为大数值孔径光子筛设计提供了一种新的设计方法。     

Imaging properties of photon sieve with a large aperture

We report the optimization design and experimental results for the imaging properties of a photon sieve, which is formed on a layer of metal film supported by a thin glass substrate. As an example, we considered a micro-optical element with parameters of diameter D=50 mm, 3,564,290 hole number, and 10 μm minimum micro-hole diameter, which was designed and fabricated by means of surface machining technique in the lab. To evaluate its imaging performance, both on-axis and off-axis imaging experiments were carried out using the element. Compared to a Fresnel zone plate lens with the same feature size, the photon sieve has super imaging performance. Some quantitative analyses and initial qualitative explanations were given for the imaging characteristics.     

Focusing contribution of individual pinholes of a photon sieve:dependence on the order of local ring of underlying traditional Fresnel zone plate

<正>A photon sieve can be composed of a large number of circular pinholes.Each circular pinhole has a contribution to the focusing.For the case of point-to-point imaging,the focusing contribution of an individual circular pinhole can be analytically given.We investigate the dependence of the focusing contribution on the order m of local ring of underlying traditional Fresnel zone plate.In particular,we find that the focusing contribution is simply inversely proportional to the order m.We also present an intuitive explanation. These results are helpful for better understanding of the focusing property of photon sieves.     

Wet-etched diffractive lenses for hard X-rays

A method for the fabrication of linear transmission Fresnel zone plates for X-rays in the 8-15 keV photon energy range is presented. The diffractive elements are generated by electron-beam lithography and chemical wet etching of (110)-oriented silicon membrane substrates. Diffractive structures with aspect ratios of more than 30 for 300 nm-wide structures were obtained. The diffraction efficiency of such a lens was measured for 13.3 keV radiation to be 20%.     

应用反射型球面菲涅耳波带片的成像物镜设计

设计了一种应用球面菲涅耳波带反射面与非球面反射面结合的成像物镜。对球面结构的菲涅耳波带反射面进行分析,推导了球面菲涅耳波带反射面近似替代非球面的方法,采用单片球面菲涅耳波带反射面和三片非球面反射面设计成像物镜,在放大倍数100×、视场角120°、菲涅耳数2.5情况下,调制传递函数在放大成像侧可实现0.6 lp/mm的40%以上,畸变小于2.2%。该设计方法为菲涅耳波带片应用于可见光成像提供了参考,并随着菲涅耳器件加工技术的不断发展具有良好的应用前景。     

Zone Plates for X-Ray Focusing (Review)

Various zone plates: amplitude, amplitude-phase, and phase ones (including Fresnel and Gabor zone plates, Laue- and Bragg-Fresnel lenses, photon sieves, and aperiodic zone plates), as well as their properties and X-ray focusing possibilities, are described and analyzed.     

Toward two-dimensional nanometer resolution hard X-ray differential-interference-contrast imaging using modified photon sieves

In this Letter, we report a significant step forward in the design of single-optical-element optics for two-dimensional (2D) hard X-ray differential-interference-contrast (DIC) imaging based on modified photon sieves (MPSs). MPSs were obtained by a modified optic, i.e., combining two overlaid binary gratings and a photon sieve through two logical XOR operations. The superior performance of MPSs was demonstrated. Compared to Fresnel zone plates-based DIC diffractive optical elements (DOEs), which help to improve contrast only in one direction, MPSs can provide better resolution and 2D DIC imaging. Compared to normal photon sieves, MPSs are capable of imaging at a significantly higher image contrast. We anticipate that MPSs can provide a complementary and versatile high-resolution nondestructive imaging tool for ultra-large-scale integrated circuits at 45 nm node and below.     

Hard X‐ray microbeam lithography using a Fresnel zone plate with a long focal length

Focused hard X‐ray microbeams for use in X‐ray nanolithography have been investigated. A 7.5 keV X‐ray beam generated at an undulator was focused to about 3 µm using a Fresnel zone plate fabricated on silicon. The focused X‐ray beam retains a high degree of collimation owing to the long focal length of the zone plate, which greatly facilitates hard X‐ray nanoscale lithography. The focused X‐ray microbeam was successfully utilized to fabricate patterns with features as small as 100 nm on a photoresist.     

Fourier treatment to the diffractive optical element composed of Fresnel zone and pinholes

Currently, the minimum feature size fabricated is about 15-40 nm. The resolution of Fresnel zone plates is limited by the width of the outermost zone. Although the photon sieves make it possible to focus soft X-rays to spot sizes smaller than the diameter of the smallest pinhole they have low diffraction efficiency. In order to foster strengths and circumvent weaknesses of them, we propose a new model which is composed of Fresnel zone and pinholes and give its fast Fourier algorithm. The simulation results demonstrate that the resolution of photon sieves is not better than that of Fresnel zone plates in low order of local rings. In this case, we can substitute pinholes for Fresnel zone in photon sieves. Resolution is nearly a constant, and also the diffraction efficiency improves.     

A super-resolution Fresnel zone plate and photon sieve

Realizing a smaller or sharper diffractive center spot is a valuable research aim in soft X-ray focus and other related research applications. Fresnel zone plates (FZP) and photon sieves (PS) are often used to focus the X-rays or other wavelength light at present. Here, we show that combination of a super-resolution phase mask (SPM) and an FZP (or PS) as one diffractive optical element can realize a smaller or sharper diffractive center spot without significantly increasing the fabrication difficulty. All these diffractive phase elements can be applied to beam shaping, mask-less lithography, energy congregation in high power lasers, soft X-rays focus, and any other field that requires a smaller or sharper diffractive center spot.     

Lacunar fractal photon sieves

We present a new family of diffractive lenses whose structure is based on the combination of two concepts: photon sieve and fractal zone plates with variable lacunarity. The focusing properties of different members of this family are examined. It is shown that the sieves provide a smoothing effect on the higher order foci of a conventional lacunar fractal zone plate. However, the characteristic self-similar axial response of the fractal zone plates is always preserved.     

Zone-doubling technique to produce ultrahigh-resolution x-ray optics

A method for the fabrication of ultrahigh-resolution Fresnel zone plate lenses for x-ray microscopy is demonstrated. It is based on the deposition of a zone plate material (Ir) onto the sidewalls of a prepatterned template structure (Si) using an atomic layer deposition technique. This results in a doubling of the effective zone density, thus improving the achievable resolution of x-ray microscopes. Test structures with lines and spaces down to 15 nm were resolved in a scanning transmission x-ray microscope at 1 keV photon energy.     

Axial intensity distribution behind a Fresnel zone plate

An analytical expression based on an improved Rayleigh–Sommerfeld diffraction formula with evanescent term is derived for analyzing the axial light intensity distribution throughout the whole space behind a Fresnel zone plate. The effects of the number of Fresnel zones and the size of aperture on the axial intensity distribution are calculated for two kinds of Fresnel zone plate with larger and smaller aperture. The validity of the general formulae for calculating the focal lengths and the relative intensities of the foci of a Fresnel zone plate is analyzed.     

连续相位变化毫米波衍射天线

基于菲涅尔原理及卡塞格伦天线设计方法,设计了一种口面直径为200 mm的卡赛格伦菲涅耳相位修正平面天线。天线采用连续相位修正方式,由一组同心菲涅耳相位修正圆环组成,与传统卡赛格伦抛物面天线相比,该天线具有平面化结构,大大减小了天线自身重量,天线辐射性能较离散相位衍射天线有大幅度提高。在95 GHz频率下,采用物理光学法进行仿真计算,并采用近场扫描系统进行了天线性能测试,天线3 dB波束宽度分别为0.95及1.05,天线实测增益为44.1 dB,天线口面效率为65%。     

Planar infrared binary phase reflectarray

A reflective, binary phase reflectarray is demonstrated in the infrared, at a wavelength of 10.6 microm. The unique aspect of this work, at this frequency band, is that the specific desired phase shift is achieved using an array of subwavelength metallic patches on top of a ground-plane-backed dielectric stand-off layer. This is an alternative to the usual method of constructing a reflective Fresnel zone plate by means of a given thickness of dielectric. This initial demonstration of the reflectarray approach at infrared is significant in that there is inherent flexibility to create a range of phase shifts by varying the dimensions of the patches. This will allow for a multilevel phase distribution, or even a continuous variation of phase, across an optical surface with only two-dimensional lithography, avoiding the need for dielectric height variations.     

Feasibility study of hard-x-ray nanofocusing above 20 keV using compound photon sieves

Combining the advantages of photon sieves (PSs) and compound Fresnel zone plates (CZPs), we designed compound photon sieves (CPSs) for hard-x-ray nanofocusing. A CPS consists of an inner PS using the first-order diffraction surrounded by an outer zone plate using the third-order diffraction. A robust digital prolate spheroidal window was used as an apodization window for the inner PS, making CPSs more flexible than CZPs. CPSs can provide not only slightly better resolution compared to CZPs, but also it can significantly suppress the sidelobes, leading to a high signal-to-noise ratio. Further improvement of the high-aspect-ratio metal nanostructure process will allow CPSs to be a promising candidate for hard-x-ray nanofocusing in the high-energy region above 20 keV.     

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.     

A Combined Phase Type Optical Element for Realizing Multiple Images

In this paper we introduce a new phase type combined optical element. The element is combined with Dammann grating and Fresnel zone plate in the same substrate by microelectronics technique, hence it has splitting functions of the Dammann grating and self-focusing function of the Fresnel plate. It can produce uniform multiple images by itself. We experimentally designed and fabricated an 9x9 multiple image element, and results show that the element can realize the multiple images we require and the intensity of each image is the same. Relative error is less than 5%.