Subsurface damage characterization in fused silica: influence of surface quality assessed by optical coherence tomography

Fused silica (FS) is a key material in precision optics due to its outstanding optical and mechanical properties. However, grinding during manufacturing introduces subsurface damage (SSD), which can impair optical performance. This study investigates SSD in FS surfaces produced by different grinding methods—pre, fine, and ultrafine—using optical coherence tomography (OCT) for non-destructive analysis. FS samples were processed with grinding tools of varying grain sizes (D126, D35, D16), and SSD characteristics were evaluated based on area threshold segmentation. The OCT measurements, performed with a Thorlabs GAN621 system, revealed clear differences in SSD depth and distribution depending on surface quality. Notably, SSD data points grouped distinctly by grinding method at area thresholds ≤ 1%, with even coarse differentiation possible at thresholds up to 10%. These findings highlight OCT’s capability to visualize and quantify SSD with high sensitivity and robustness, making it a valuable technique for quality control in optical fabrication. The study underscores the correlation between grinding technique and SSD characteristics, emphasizing the importance of tailored processing to minimize subsurface defects and enhance component reliability.