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J. Eur. Opt. Society-Rapid Publ. 21, 22( 2025)
Figure 1. Absorption spectrum of fused silica at room temperature, based on Yang, S. et al. [ 24 ].
Figure 2. Absorption spectrum of water from UV to IR region, based on Ozaki, Y. et al. [ 26 ].
Figure
3. Transmission measurements for different cooling lubricants( Kluthe Hakuform, Blaser Synergy 915, Cimtech D18FF). the angles of incidence, leading to enhanced absorption. In general, scatter from optical components can propagate in any direction over the entire observation sphere centered about the sample. The distribution of light within the scatter pattern is a function of incident angle and wavelength as well as sample parameters such as orientation, transmittance, reflectance, absorptance, surface finish, index of refraction, bulk homogeneity, contamination, etc. [ 25 ]. The selection of the specific wavelength of 1 lm provides a precise framework for investigating the relationship between roughness and absorption behavior under practical conditions.
Another key advantage of using a fiber laser with a wavelength of 1070 nm in the planned laser-assisted grinding of glass is its low absorption by water, a primary component of the coolant lubricant necessary in mechanical abrasion processes on glass. In contrast, CO 2 laser radiation at 10.6 lm is highly absorbed by water( Fig. 2). The low absorption characteristic of the fiber laser enables more efficient energy transfer directly to the glass surface, with minimal energy loss within the coolant lubricant.
The high transmission of water to the fiber laser’ swavelength ensures that the coolant lubricant fully retains its cooling and lubricating functions. This prevents issues such as local overheating or vaporization within the liquid medium, which are common with CO 2 lasers.
Therefore, measurements were conducted with a solidstate laser(“ CW-M R4 RS” from company SPI; laser output power 50 – 500 W) to evaluate the impact of coolant lubricants on the laser transmission reaching the glass sample. Water served as a reference, alongside the lubricants Kluthe Hakuform( 1.5 % concentration), Blaser Synergy 915( 6 % concentration), and Cimtech D18FF( 3 % concentration), with all tests performed under identical conditions and each lubricant with a scope of three measurements. The concentration values were chosen based on the manufacturer’ s recommendations.
In the experiments, the transmitted laser power was examined for liquid columns with a height of 0 – 16 mm. For column heights between 0 and 4 mm, all tested lubricants showed high transmission efficiencies of 90 % to 97 %( Fig. 3). For grinding processes, the column height would not exceed 1 – 2 mm. This indicates that within this height range, the coolant lubricants have minimal impact on laser transmission, ensuring efficient energy delivery to the glass sample.
Given the promising results of the laser transmission for the cooling lubricants due to their low absorption by water, the fiber laser was selected for further investigations. This advantage is particularly valuable when considering future grinding applications, where effective cooling and energy efficiency are critical.
3 Experimental set up
Investigations were carried out into the interaction of laser radiation from a solid-state laser(“ CW-M R4 RS” from company SPI Lasers UK Ltd( now: TRUMPF SE + Co. KG); laser output power 50-500 W; continuous wave mode) with the surface of planar samples, with focus on fused silica