GOALI: High resolution diffractive x-ray optics

雅各布森：电磁辐射的最终焦点是什么？透镜的远场聚焦可以用其瑞利分辨率来表征，其瑞利分辨率为0.61倍波长除以透镜开口角的一半，即数值孔径。为了获得比可见光激光和大数值孔径显微镜物镜(例如在共焦显微镜中)获得的更精细的聚焦，必须在保持可察觉的数值孔径的同时显著减小波长。这可以通过使用X射线的短波长，以及使用衍射光学来保持合理的高数值孔径来实现。菲涅耳x射线波带片是一种衍射聚焦光学元件，可以在任何波长产生最好的远场电磁辐射焦点--在2-5 nm波长下的瑞利分辨率约为35 nm。这些波带板是由纽约州立大学石溪分校物理和天文学系的一个小组和朗讯技术贝尔实验室的Don Tennant最先进的电子束曝光组之间的学术和工业合作制造的，该小组使用附近Brookaven国家实验室的国家同步辐射光源(NSLS)进行X射线显微镜研究。通过这种合作生产的波带片被用作NSLS的三个X射线显微镜系统的聚焦光学元件，这些显微镜被Stony Brook小组以及一些美国和欧洲小组使用，用于使用X射线显微镜进行生物、聚合物科学、地球科学、胶体化学、环境科学和其他领域的研究。鉴于X射线微聚焦在包括布鲁克海文、阿贡、伯克利、斯坦福、康奈尔、威斯康星大学和路易斯安那州立大学在内的美国同步辐射设施中的重要性日益增长，并且这些设施中的每一个代表2000-5亿美元的投资，在美国的学术环境中进一步开发制造可能最高分辨率波带片所需的工艺似乎是至关重要的。事实上，X射线显微镜的大量潜在应用(在0.2-1keV能量范围内，以及1-10keV的能量范围)，如果波带片的空间分辨率大大提高到现在所能达到的范围，将成为可能。PIS的研究计划包括：o他们计划向世界领先的超快X射线脉冲产生小组之一提供波带板：科罗拉多大学JILA的玛格丽特·穆尔纳内和亨利·卡佩廷的实验室。这应该能够在不同于热核武器的环境中首次探索x射线波长下的非线性光学。o他们建议开发波带片，首次使1-10keV x射线显微镜可以常规获得低于100 nm的分辨率成像。在这个能量范围内的显微镜非常适合于生物和环境科学中的痕量元素绘图，以及集成电路中掩埋互连中的缺陷检查。o他们建议进行针对未来Bragg波带板发展的实验测试，其中高纵横比区域必须倾斜到处于Bragg条件下，以实现高聚焦效率和非常高的数值孔径。o他们建议与纳米压印光刻领域的领先团队(德克萨斯大学奥斯汀分校)合作，将我们在精细线宽波带板制造方面的能力与他们的高通量光刻制造技术相结合。最终的目标是制造有限数量的高分辨率母版波带片，并使用UTA纳米压印方法来制造“一次性”高分辨率波带片。这可能是一个高风险、高回报的科学项目的关键技术：使用x射线自由电子激光来获得膜蛋白结构的原子分辨率图。

0099893JacobsenWhat is the ultimate focus of electromagnetic radiation? The far-field focus of a lens can be characterized by its Rayleigh resolution of 0.61 times the wavelength divided by half of the lens' opening angle, or numerical aperture. To achieve a finer focus than that obtained from a visible light laser and a high numerical aperture microscope objective (such as in a confocal microscope), one must significantly decrease the wavelength while still maintaining appreciable numerical aperture. This can be accomplished by using x rays for their short wavelength, and diffractive optics for maintaining a reasonably high numerical aperture. Fresnel x-ray zone plates have been fabricated as diffractive focusing optics that produce the finest far-field focus of electromagnetic radiation at any wavelength - about 35 nm Rayleigh resolution at 2-5 nm wavelength. These zoneplates have been fabricated in an academic-industrial collaboration between a group at the Department of Physics and Astronomy at SUNY Stony Brook that carries out research in x-ray microscopy using the National Synchrotron Light Source (NSLS) at nearby Brookhaven National Laboratory, and the state-of-the-art electron beam lithography group of Don Tennant at Lucent Technologies Bell Laboratories. Zone plates produced by this collaboration are employed as the focusing optics in three x-ray microscope systems at the NSLS, and these microscopes are used by the Stony Brook group and by a number of U.S. and European groups for research in biology, polymer science, geoscience, colloid chemistry, environmental science, and other fields using x-ray microscopy. Given that x-ray microfocusing is growing in importance at U.S. synchrotron radiation facilities including those at Brookhaven, Argonne, Berkeley, Stanford, Cornell, University of Wisconsin, and Louisiana State University, and that each of these facilities represents an investment of $20-500 million, it seems crucial to further develop the processes needed for fabrication of the highest possible resolution zone plates within an academic setting in the U.S. Indeed, a large number of potential applications of x-ray microscopes (both in the 0.2-1 keV energy range, and the 1-10 keV energy range) would become possible if the spatial resolution of zone plates were to be increased significantly beyond what is now attainable. The PIs research program includes the following:o They propose to supply zone plates to one of the world's leading groups in ultrafast x-ray pulse generation: the lab of Margaret Murnane and Henry Kapetyn at the University of Colorado/JILA. This should enable the first exploration of nonlinear optics at x-ray wavelengths in a setting other than that of a thermonuclear weapon.o They propose to develop zone plates that should, for the first time, make sub-100 nm resolution imaging routinely available for 1-10 keV x-ray microscopes. Microscopes in this energy range are ideal for trace element mapping in biology and environmental science, and for inspection of defects in buried interconnects in integrated circuits.o They propose to carry out experimental tests aimed at future development of Bragg zone plates, where high aspect ratio zones must be angled to be on the Bragg condition to achieve high focusing efficiency and very high numerical aperture.o They propose to work with one of the leading groups in nanoimprint lithography (University of Texas at Austin) to combine our capabilities in fine linewidth zone plate fabrication with their technology for high throughput lithographic fabrication. The ultimate goal is to make a limited number of high resolution "master" zone plates, and use the UTA nanoimprint method to fabricate "disposable" high resolution zone plates. This could be a key technology for a high-risk, high-payoff scientific project: the use of x-ray free electron lasers to obtain atomic resolution maps of the structure of membrane proteins.