Non-Destructive Estimation of Subsurface Glass Damage Using Fluorescent Confocal Microscopy

The processes of cutting, grinding and polishing optical materials cause fractures that extend some depth below the surface. The unrelieved strain and deep cracks present below the surface can seriously affect the performance of an optical system, especially in applications requiring precision optics. Subsurface damage (SSD) can lower image contrast, cause figure instability, and contribute to catastrophic fracture in high-power lasers [1]. Different optical materials present different forms of physical damage. Techniques used to increase productivity, such as high feed rates and high lap pressures, are the most serious causes of SSD [2]. An easily employed and non-destructive SSD measurement is important for the improvement of optical fabrication techniques.