J. Eur. Opt. Society-Rapid Publ. 2025, 21, 22 Ó The Author( s), published by EDP Sciences, 2025 https:// doi. org / 10.1051 / jeos / 2025020 Available online at: https:// jeos. edpsciences. org
EOSAM 2024 Guest editors: Luca De Stefano and Raffaele Velotta
Journal of the European Optical Society-Rapid Publications
RESEARCH ARTICLE Investigations into temperature measurement in a laser-based heating process of optical, machined components
Sarah Koch a,*, Sebastian Henkel a, Daniel Knoche, Michael Güpner, Christian Schulze, Thekla Boeckh, and Jens Bliedtner
University of Applied Sciences Jena, Carl-Zeiss-Promenade 2, 07745 Jena, Germany
Received 31 January 2025 / Accepted 15 April 2025
Abstract. The manufacturing of optical components is subject to constant efforts to optimize production processes in order to achieve high surface qualities under the most economical conditions possible. This includes the refinement of existing technologies or development of completely new production technologies. One possible approach is the combination of conventional machining processes for optical components like diamond turning, grinding or polishing with laser-based processes to thermally influence the surface for improved machining or surface properties. For this, knowledge of the thermal interactions of the laser on the component surface is needed, which in turn requires its metrological acquisition. In this work, measurements were carried out using various methods for the controlled heating of glass surfaces by an infrared laser( k = 1070 nm). Among other things, a clear correlation between the samples surface roughness and the laser absorption is found.
Keywords: Solid state laser, Infrared laser, Fused silica, Temperature measurement, Roughness.
1 Introduction
Hard brittle materials, such as fused silica, optical glasses and crystals, various types of ceramics and glass ceramics, represent a promising field of materials for the future due to their diverse uses in a wide range of high-tech applications. However, machining these materials is still a major challenge due to their brittle machining behavior, as the requirements for the components to be manufactured are constantly increasing in terms of surface quality, cleanliness and dimensional accuracy [ 1, 2 ]. At the same time, the component geometries to be produced are increasingly characterized by a high degree of complexity( free-form surfaces, monolithic components) [ 3, 4 ]. Usually, the process chain in the production of components in the field of optical technologies consists of many grinding, lapping and polishing steps, with which the surface quality is gradually increased [ 5, 6 ].
Grinding in particular is an important process step here, as it is used both for shaping and for creating polishable surfaces due to its high precision [ 7 ]. Grains made of high-hardness materials such as diamond or corundum are used, which serve as wedges that exert pressure on the material during a relative movement between the tool and the component and generate microcracks. The cracks created
a These authors contributed equally to this work. * Corresponding author: Sarah. Koch @ eah-jena. de continue to spread and lead to fracture formation, which results in the corresponding material removal [ 8 ]. This type of chip removal is referred to as brittle material behavior. In addition, plastic deformation processes, which are referred to as ductile material behavior, can also take place. In addition to the geometry and size of the cutting grains, as well as the interaction of feed rates, infeed and the cutting speeds used, the material removal mechanism essentially depends on the cutting engagement, i. e. the penetration depth of the grain cutting edges involved. If this increases and exceeds the critical chip thickness, the ductile machining process is abandoned and the brittle material behavior becomes predominant [ 8 – 10 ]. However, it is problematic that machining in the brittle fracture regime in particular also induces a large number of microcracks and defects in the area below the component edge zone, which are referred to as subsurface damage( SSD) and can lead to a reduction in the performance and service life of high-performance components [ 11 – 13 ]. Avoiding and reducing this crack depth damage is therefore a central task of modern optics production. These should only be so deep that they can be removed in the subsequent process steps of lapping and polishing.
For this reason, ductile grinding is aimed as a last step in surface generation with bound grain, as the formation of microcracks in the interaction zone can be avoided by ductile material behavior and it is possible to produce damage-free component edge zones with high surface
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