J. Eur. Opt. Society-Rapid Publ. 21, 22( 2025) 217
Figure 4. Experimental configuration including a thermography camera, contact thermometer and laser power meter.
Table 1. Roughness values of defined, differently prepared fused silica sample surfaces.
Fused silica samples |
Rq [ lm ] |
Sample nr. |
Preparation method |
Mean value |
Std. Deviation |
1 |
Polished |
0.001 |
0.000 |
2 |
Fine ground D35 |
0.289 |
0.038 |
3 |
Fine ground D64 |
0.438 |
0.130 |
4 |
Medium ground D64 |
0.728 |
0.134 |
5 |
Lapped F400 |
0.790 |
0.035 |
6 |
Rough ground D64 |
0.990 |
0.138 |
7 |
Lapped F230 |
2.177 |
0.214 |
8 |
Rough ground D126 |
2.966 |
0.535 |
( SiO 2)( Ø 49 mm; thickness 6 mm). The samples were measured each on three positions with a white light interferometer( TopMap Micro. View, company PolyTec) to define the surface conditions. A collimated beam diameter of 8.7 mm was applied.
The absorbance related heat induction into the glass specimen was monitored at the surface and compared between a contact thermometer“ DTM3000” and a noncontact thermographic device“ Optris PI 450i”( spectral range 8 – 14 lm). The samples were placed with their surface horizontally orientated in a holder, enabling also a measurement of the transmitted laser power below the sample( laser power meter“ 1000W-Bb-34”, company Ophir). All measurement positions and angles were fixed during the investigations and each had a number of measurements of three. The maximum values for temperature and power were measured while the laser process was still active. The motivation behind using three measuring devices in one process is the comparison between quantitative values of different measurement devices / principles for assessment of the thermal absorption behavior. Figure 4 shows the described set up all positioned within the grinding machine(“ SM 80 Digital”, company OptoTech) that will be used as an experimental machine for laser-assisted grinding later.
Figure 5. Temperature increase in roughness dependent sample heating by solid state laser( 500 W for 30 s), measured by contact thermometer.
A main focus was set on the influence of surface quality on laser absorption and therefore surface heating. For this, the samples were processed differently prior to the investigations by either polishing, lapping with silicon carbide loose grain or grinding with different parameters and diamond grain sizes to achieve defined, clearly distinguishable