Laser-induced swelling of transparent glasses

We describe the process of forming bumps on the surface of transparent glasses such as display glasses with moderate thermal expansion ∼3.2 × 10⁻⁶ K⁻¹ and high coefficient of thermal expansion (CTE) glasses, e.g. soda-lime glasses with CTE ∼9 × 10⁻⁶ K⁻¹ using high-power ultra-violet (UV) lasers at a wavelength where glass is transparent. We characterize the effect with optical dynamic measurements. The process relies on increased glass absorption from color-center generation and leads to glass swelling with bumps formation. The bump height may constitute more than 10% of the thickness of the glass sample. The required exposure time is relatively short ∼1 s, and depends on the glass properties, laser power, its repetition rate, and focusing conditions. A brief review of the potential applications for these bumps is provided.