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Fundamental Study of Ultra-Precision Machining and Near Surface Damage Evolution in Single Crystal Fluorides for Advanced Optics

先进光学用单晶氟化物超精密加工和近表面损伤演化的基础研究

基本信息

批准号：
1727244
负责人：
Don Lucca
金额：
$ 35.71万
依托单位：
Oklahoma State University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-10-01 至 2023-09-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1727244&HistoricalAwards=false
关键词：
Fundamental Study Ultra Precision Machining

项目摘要

Single crystal calcium fluoride is one of only a few materials that can be used for optics (lenses) which require the transmission of ultraviolet light. This is a result of its exceptionally low absorption in the ultraviolet spectral region. Optics produced from calcium fluoride are typically machined using an ultra-precision machining process with single crystal diamond tools, referred to as diamond turning. This machining process introduces near surface damage which increases the material's absorption of ultraviolet light. The mechanisms responsible for the degradation of optical quality caused by machining are not scientifically understood. This lack of understanding is limiting applications where diamond turning, as opposed to polishing, is required, for example, for nanometer precision aspheric or free-form optics. This study will contribute to new fundamental understanding of both the nature and extent of subsurface damage introduced into these brittle, optical materials by diamond turning. It is envisioned that the findings of this work will be applicable to a range of single crystal alkaline earth fluorides which are finding emerging uses in optical applications. The project is an international collaboration between Oklahoma State University (OSU), the Laboratory for Precision Machining (LFM) at the University of Bremen, Los Alamos National Laboratory (LANL) and Carl Zeiss Jena GmbH. NSF is only providing funding for the work done by OSU, but leverages research facilities not available in the US to the benefit of US innovation in several several sectors, most notably the ultraviolet optics used for lithograph in integrated circuit production. This represents a very large industry in the United States, and the results of this fundamental research could provide significant tangible benefits to the domestic economy. The international collaboration also provides a unique exposure of an American graduate student to manufacturing research at the highest levels of sophistication in both Germany and the US. The research objective of this research study is to test the hypothesis that the degradation in optical performance of single crystal calcium fluoride, which has been finished by ultra-precision machining, is directly related to the nature and extent of the near surface damage introduced. Ultra-precision machining experiments based on linear planing with round nose single crystal diamond tools will be used to determine the critical depth of cut to produce a non-fractured surface for a given crystal orientation. Based on these findings, linear planing and face turning experiments will be performed to generate surfaces for which the surface and subsurface state can be evaluated. Channeling Rutherford backscattering spectrometry (channeling RBS), cross-sectional transmission electron microscopy (XTEM) and high resolution transmission electron microscopy (HR-TEM), and x-ray diffraction (XRD) will be used to provide a quantitative characterization of the subsurface. The optical performance of the surface will then be assessed by measuring transmissivity using Ultraviolet-Visible (UV-Vis) spectroscopy and birefringence using a polarimeter allowing for the establishment of a quantitative link between spectrally resolved optical performance and subsurface damage to be made.

单晶氟化钙是少数几种可用于需要透射紫外光的光学（透镜）的材料之一。这是由于其在紫外光谱区的吸收极低。由氟化钙生产的光学器件通常使用单晶金刚石工具的超精密加工工艺进行加工，称为金刚石车削。这种加工过程会导致近表面损伤，从而增加材料对紫外线的吸收。机械加工导致光学质量下降的机制尚未得到科学的理解。这种缺乏理解限制了金刚石车削而不是抛光的应用，例如，纳米精度非球面或自由曲面光学器件。这项研究将有助于对金刚石车削引入这些脆性光学材料的亚表面损伤的性质和程度有新的基本认识。据设想，这项工作的结果将适用于一系列的单晶碱土金属氟化物，这是发现在光学应用中的新兴用途。该项目是俄克拉荷马州州立大学（OSU）、不莱梅大学精密加工实验室（LFM）、洛斯阿拉莫斯国家实验室（LANL）和卡尔蔡司耶拿有限公司之间的国际合作。NSF只为俄勒冈州立大学所做的工作提供资金，但利用美国没有的研究设施，使美国在几个领域的创新受益，最值得注意的是用于集成电路生产光刻的紫外光学。这在美国是一个非常大的产业，这项基础研究的结果可以为国内经济带来显著的实际利益。国际合作还提供了一个独特的美国研究生接触制造业研究在德国和美国的最高水平的复杂性。本研究的研究目的是检验以下假设：单晶氟化钙的光学性能的退化，这已经完成了超精密加工，是直接相关的性质和程度的近表面损伤介绍。超精密加工实验的基础上，线性刨圆鼻子单晶金刚石工具将被用来确定临界深度的切割，以产生一个非断裂表面为一个给定的晶体取向。基于这些发现，将进行线性刨削和面车削实验，以生成表面和表面下状态可以评估的表面。将使用散射卢瑟福背散射光谱法（沟道RBS）、横截面透射电子显微镜（XTEM）和高分辨率透射电子显微镜（HR-TEM）以及X射线衍射（XRD）对表面下进行定量表征。然后，通过使用紫外-可见（UV-Vis）光谱法测量透射率和使用偏振计测量双折射率来评估表面的光学性能，从而在光谱分辨的光学性能和要进行的表面下损伤之间建立定量联系。