Investigation of subsurface damage impact on resistance of laser radiation of fused silica substrates

Abstract

In this work we report an experimental investigation of subsurface damage (SSD) in conventionally polished fused silica (FS) substrates which are widely used in laser applications and directly influence performances of optical elements. Two procedures were developed: 1 -acid etching and 2 -superpolishing. Additionally, surface roughness and total integrated scattering (TIS) measurements were performed to find correlation between the main surface properties and laser induced damage threshold (LIDT) as circumstantial evidence of elimination of SSD.Different durations of acid etching have been used to study LIDT of FS substrates. These experiments revealed that the optimal etching time is ~1 min. for a given acid concentration. Laser induced damage threshold of etched and SiO 2 layer coated FS samples increased ~3 times, while of the ones that were not coated -4 times. It has been revealed that for nonetched surface a single nano-to micro-scale absorbing defect ensemble most likely associated with polishing particles within Beilby layer was dominant, while damage morphology in ~1 min etched FS sample had no point defects observed.More than 5 times lower roughness value (RMS) was obtained by superpolishing procedure using colloidal silica abrasive particles. LIDT of such superpolished fussed silica substrates was also strongly increased and compared with conventional CeO 2 abrasive polishing.

Characterization of the Polishing‐Induced Contamination of Fused Silica Optics

“…XPS spectra showing the core level Ce 3d binding energy are shown in Figure 4A. The As mentioned by Juskevicius et al, 23 the intensity of XPS signal was very low which means that the cerium concentration is very low. Because of this very small signal, we could not quantify the cerium contamination and we chose to plot the signal in counts per second ( Figure 4B) instead of the estimated concentration in atomic percent.…”

“…As mentioned by Juskevicius et al., the intensity of XPS signal was very low which means that the cerium concentration is very low. Because of this very small signal, we could not quantify the cerium contamination and we chose to plot the signal in counts per second [Fig.…”

The scaling potential of beam-splitter-based coherent beam combination

“…14 already was optimized for least absorption in terms of the coating materials and the general coating process, but even more aspects influence the residual absorption. For example, superpolishing [25,26], removal of damage precursors during the coating process [27], and the minute minimization of the hydroxyl content in the coating layers might allow to reduce this absorption contribution even further and, with that, to increase the combined-beam average power.…”

Ultrafast Process Characterization of Laser-Induced Damage in Fused Silica Using Pump-Probe Shadow Imaging Techniques

“…With the continuous increase in laser power, these components are susceptible to damage under intense laser irradiation, significantly affecting the laser system's lifespan and safe operation [1]. Currently, damage to fused silica often occurs on the component's surface, and it is widely acknowledged in the scientific community that this is closely associated with surface defects in fused silica [2][3][4]. These defects comprise two main categories: mechanical defects introduced during the fabrication process [5][6][7] and contaminative defects [8][9][10].…”