Study on the femtosecond laser-induced refractive index change in a silicate glass by transient lens method

When a laser pulse is tightly focused inside a transparent solid material, a permanent structural change occurs in the focused region. This phenomena will be very useful to construct many important devices such as integrated optical waveguides, or three-dimensional photonic devices. The mechanism of the light induced structural change inside a glass was investigated in a picosecond-nanosecond region by a transient lens technique with an intense subpicosecond pulsed laser and microscope objective lens. Just after the irradiation of the pump pulse inside the glass, a concave lens was instantaneously created. After this fast response signal, an oscillation with some different frequencies in GHz region was observed. The origin of the oscillation is discussed. (C) 2003 American Institute of Physics.