Ultrafast laser produces permanent optical waveguides in bulk glass

Ultrafast laser produces permanent optical waveguides in bulk glass

Researchers at the Hirao Active Glass Project (Kyoto, Japan) fabricated permanent waveguides in various bulk glasses by focusing 120-fs pulses from a regeneratively amplified Ti:sapphire laser system through a microscope objective and translating the glass sample parallel to the axis of the laser beam. The laser pulse photoinduced a refractive-index change in the glass. The laser wavelength was 800 nm, peak power was 109 W, and the glass sample was translated at a rate of 20 µm/s. The refractive-index changes were induced along the path traversed by the focal point, and the waveguides were written inside glasses such as fused and synthetic silica, germanium-doped silica, fluoride glasses, and others. The researchers also found that control of the refractive-index difference and core diameter was possible by adjustment of the writing conditions, such as the average power of the writing laser. Single-mode propagation was seen for small core diameters, while higher-order modes were observed with an increase of the core diameter. The work suggests new possibilities in integrated optics and three-dimensional optical circuits, especially in the area of compact, all-solid-state lasers, amplifiers, and switches.