Motion of bubble in solid by femtosecond laser pulses

We report that irradiation of femtosecond laser pulses moves a microscopic bubble inside crystalline calcium fluoride and amorphous silica glass. In situ observation revealed that the bubble moves against the direction of propagation of laser pulses as far as 2 microns. We also demonstrate the lateral movement of a void along the axis perpendicular to the beam propagation axis by shifting the laser focus.