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Material Selection
Published in Daniel Vukobratovich, Paul Yoder, Fundamentals of Optomechanics, 2018
Daniel Vukobratovich, Paul Yoder
Crown glasses are the lowest in cost, with the highest thermal expansion coefficient, and are used in environments where thermal performance is not important. The thermal expansion coefficient of borosilicate crown glasses, including Corning Pyrex 7740, Schott Duran 50, and Ohara E-6, is between 2.8 and 3.3 × 10−6 K−1, which is about 40% of that of the crown glasses. The thermal coefficient of expansion curves of the zero-coefficient-of-expansion materials, such as Schott Zerodur and Sitall 115, are zero crossing near room temperature. This zero crossing occurs only at one temperature and is not useful. Over a more reasonable temperature range of ±60°C, the effective thermal coefficient of expansion of these materials can be as low as 30 × 10−9 K−1 for Corning ULE 7972.
Antireflection Coatings
Published in H. Angus Macleod, Thin-Film Optical Filters, 2017
Antireflection coatings can range from a simple single layer, having virtually zero reflectance at just one wavelength, to a multilayer system of more than a dozen layers, having reduced reflectance over a range of several octaves. The type used in any particular application will depend on a variety of factors, including the substrate material, the wavelength region, the required performance, and the cost. In the visible region, crown glass, which has a refractive index of around 1.52, is most commonly used. As we shall see, this presents a very different problem from infrared materials, which can have very much higher refractive indices.
Improved CNC ball-end magnetorheological finishing process for borosilicate glass polishing
Published in Materials and Manufacturing Processes, 2023
Mohsen Derakhshan-Samani, Abdolreza Rahimi
The final finishing operations are considered the most influential process for precise manufacturing and play a crucial role in production quality, strength, and reliability[1]. With the development of advanced materials and their applications, demand for components with nano-level surface finishing to meet particular necessities in their application has increased.[2] Pure borosilicate-crown glass (BK7) is one of the best-known glasses used in the optical industry. Because of its mechanical and optical characteristics, the use of BK7 has become increasingly common over the past two decades. There are increasing requests for magnetically nano-finishing methods for BK7 lens production in the Optical industries. One of the recent common issues that researchers have shown an increased interest in is nano-polishing BK7 lenses with the aid of modern magnetorheological finishing processes.[3]