Overcoming Processing and Polishing Challenges in Calcium Fluoride Precision Optics

The increasing demand for low-surface-roughness precision optics in advanced optical systems places stringent requirements on polishing processes, particularly for materials with challenging mechanical properties. Calcium fluoride (CaF2) is widely used in ultraviolet and infrared optical applications due to its broad spectral transparency, making it a key material for spectroscopy, imaging, and multi-wavelength optical systems. Achieving the required surface quality on CaF2, however, remains challenging due to its low hardness and brittle nature, which can lead to edge chipping, subsurface damage, and inconsistent surface finish.

Cerium oxide abrasives are commonly used in optical polishing because of their combined chemical and mechanical activity. In CaF2 processing, however, cerium oxide can leave surface-bonded residues that are difficult to remove and may increase absorption in the ultraviolet spectral range, limiting suitability for certain applications.

This presentation examines alternative abrasive approaches for CaF2 polishing using diamond- and alumina-based suspensions. A systematic study is presented in which CaF2 substrates are processed from ground surfaces to final polish using diamond abrasives with particle sizes of 3 µm and 0.25 µm in combination with different polishing pad materials. Surface quality, and process efficiency are evaluated to assess the suitability of these abrasive systems for both bulk material removal and final finishing.

About the presenter
Caroline Wattinez is the group leader of US Innovation and has worked at Pureon since January 2022. At Pureon, she has worked on the development of consumables for the grinding and polishing of precision optics and other semiconductor materials.

Before Pureon, Wattinez completed her master’s degree in chemical engineering as well as her bachelor’s degree in chemistry at The Ohio State University.