Optical glass polishing by controlled laser surface-heat treatment

Abstract

It is shown that optical surfaces traditionally ground in conventional glasses with high coefficients of thermal expansion may be polished by irradiation with a space- and time-controlled uniform CO(2) laser beam. Comparisons of a theoretical simulation model of the laser-driven heating process with the experimental results allow us to determine the conditions for successful and reliable use of this technique. The technique can be applied indiscriminately to preheated samples made of different glasses, with any topography, and, of any size in a limited range that depends only on the available laser power.

Contact mechanics for randomly rough surfaces

“…The angular brackets ... in (14) stands for ensemble average or, what is in most cases equivalent, average over the surface area…”

Laser micro-fabrication of concave, low-roughness features in silica

“…This was recognized as an efficient way to polish optical surfaces. 1,2 Owing to the surface-minimizing effect of the surface tension, melting of large-scale domains which penetrate considerably into the volume will result in the formation of convex structures. While this behaviour has been successfully employed for the fabrication of convex micro-optical structures, [3][4][5][6] it is undesired in the context of surface polishing.…”

Fabrication of mirror templates in silica with micron-sized radii of curvature

“…With low irradiation, ablation becomes negligible whereas surface-tension-induced smoothing remains effective. 20 The protocol is sketched in Figure 2. Photoresist (AZ1512HS) is spun onto a flat silica substrate (f) and locally removed by means of standard photolithography in order to expose the underlying silica for a substrate-selective RIE step (CHF 3 /Ar/ O 2 ) (g).…”