By: Kazuyoshi Itoh, YasuyukiOzeki
Department of Material and Life Science, Osaka University
Focused ultrafast laser pulses can cause a variety of the structural modifications including void, damage, refractive index (RI) change, and crack, depending on materials and irradiation conditions such as pulse energy, pulse width and numerical aperture (NA) of the focusing lens. Among these modifications, the RI change is interesting especially for the application to micro-fabrication of 3D photonic devices inside glass. The RI change occurs as a result of localized melting and rapid re-solidification. Fused silica shows positive RI change, allowing us to fabricate waveguides in glass. Other devices such as diffractive optical elements (DOE’s) can be fabricated regardless of the sign of RI change. We review this technique focusing on the fabrication of photonic devices (see Fig. 1).