Micro Optical Elements Formed by CO₂ Laser Irradiation on Densified Silica Glass

Abstract

Silica glass was densified by applying high-pressures and temperatures. Small area at the surface of the densified glass was relaxed by irradiating focused CO₂ laser beams. A bump having Gaussian shape was formed after the irradiation. Refractive index around the bump center was almost constant at the surface. A center region of bump acted as a convex lens and focused light, although a peripheral region acted as a concave lens and defocused light. The optical performance is due to the refraction of light at the bump surface and to the inflection of light by the gradient of refractive index inside the glass.