This paper presents a novel micro-fabrication method using focused ultraviolet (UV) light to manufacture three-dimensional sawtooth structures in ultra-thick negative photoresist to fabricate a novel multi-prism x-ray lens. The method uses a lens to shape the UV beam instead of the photomask conventionally used in UV lithography. Benefits of this method include the ability to manufacture sawtooth structures in free form, for example in circular shapes as well as arrays of these shapes, and in resist that is up to 76 μm thick. To verify the method, initially a simple simulation based on Fourier optics was done to predict the exposure energy distribution in the photoresist. Furthermore, circular sawtooth gratings were manufactured in a 76 μm SU-8 resist. The UV lens was fabricated using electron beam lithography and then used to expose the SU-8 with UV light. This paper details the complete developed process, including pre-exposure with an e-beam and cold development, which creates stable sawtooth structures. The measured profile was compared to the ideal sawtooth and the simulation. The main discrepancy was in the smallest feature size, the sawtooth tips, which were wider than the desired structures, as would be expected by simulation.

Effective collecting area, angular resolution, field of view and energy response are fundamental attributes of X-ray telescopes. The performance of state-of-the-art telescopes is currently restricted by Wolter optics, especially for hard X-rays. In this paper, we report the development of a new approach -the Stacked Prism Lens, which is lightweight, modular and has the potential for a significant improvement in effective area, while retaining high angular resolution. The proposed optics is built by stacking discs embedded with prismatic rings, created with photoresist by focused UV lithography. We demonstrate the SPL approach using a prototype lens which was manufactured and characterized at a synchrotron radiation facility. The design of a potential satellite-borne X-ray telescope is outlined and the performance is compared to contemporary missions.Since the first orbiting X-ray telescope, the Einstein Observatory, was launched in 1978, focusing X-ray telescopes (XRTs) have provided new knowledge on the universe by observing remote objects in the X-ray spectrum 1, 2 . The performance of XRTs is mainly determined by the optics. State-of-the-art focusing XRTs rely on Wolter optics, for which X-rays that are nearly parallel to the nested mirrors are collected by total external reflection. This has been successfully employed in several telescopes (e.g. Chandra 3 , XMM-Newton 4 , Swift 5 and the planned ATHENA mission 6 ), for X-rays in the energy range of 0.1 to 10 keV with high values of efficiency, angular resolution and sensitivity. However, for X-ray energies higher than 10 keV, using the same technique compromises spatial resolution and efficiency since the grazing angle quickly decreases with energy, making the focal length of the system impractically long and the field of view (FoV) very small. Moreover, the efficiency of the mirrors decreases, and nesting becomes more difficult. To mitigate this issue, it is possible to use multi-layered coatings and Bragg-reflection from depthgraded multi-layers to increase the grazing angle in the hard X-ray energy range 7, 8 . Current hard X-ray focusing telescopes such as NuSTAR 9 and Astro-H 10, 11 are designed this way. Although this provides a significant improvement in performance for hard X-rays, the long focal length is challenging when designing missions, and the small effective collecting area and narrow FoV limits the scientific return from missions. In addition, the angular resolution is severely influenced by 1 arXiv:2002.02299v1 [astro-ph.IM] 6 Feb 2020 figure error, surface roughness and assembly precision 2 .At present, refractive 12, 13 and diffractive transmissive X-ray optics 14 have been used in a wide range of applications [15][16][17] , such as biology 18 , chemistry 19 and lithography 20,21 . Several novel zone plates 14 , such as multilayer zone plates 22-25 , interlaced zone plates 26 and stacked zone plates 27 , as well as refractive optics, such as commercially available compound refractive X-ray lenses 13 , have been developed for hard X-ray ima...

Grayscale electron beam lithography is an important technique to manufacture three-dimensional (3D) micro- and nano-structures, such as diffractive optical devices and Fresnel lenses. However, the proximity effect due to the scattering of electrons may cause significant error to the desired 3D structure. Conventional proximity correction methods depend on the exposure energy distribution which sometimes is difficult to obtain. In this study, the authors develop a novel proximity effect correction method based on multivariate adaptive regression splines, which takes exposure energy and development into consideration simultaneously. To evaluate the method, a Fresnel lens was fabricated through simulation and experiment. The measurements demonstrate the feasibility and validity of the method.