Femtosecond laser modification of glass

Tight focusing of ultrashort (∼100 fs) infrared laser pulses of moderate energy (typically 1–10 μJ) into a glass results in very high, localized (in space and time) intensities, in excess of 1014 W/cm2. Under these conditions the laser–materials interaction becomes highly nonlinear, resulting in permanent modification of the material. By precisely controlling sample position and movement it is possible to optically ‘write’ three-dimensional patterns inside a glass. The modified glass can differ from the unmodified material in a wide variety of properties including refractive index, absorption coefficient, nonlinear optical susceptibility, crystal structure, morphology etc. In this paper, I discuss how ultrafast laser modification of glass can be used to add new functionality to glasses. The structures that can be fabricated with the ultrafast laser writing technique have applications in optical data storage, telecommunications and bio-sensing and -imaging.