Three dimensional micromachining inside a transparent material by single pulse femtosecond laser through a hologram

A basic pattern of a three dimensional (3D) photonic crystal, which consists of 16 capsule shaped elements in eight layers, is formed inside a silica glass using only a single pulse femtosecond laser through a computer generated hologram. The three parameters indispensable to the completely flexible 3D patterning, namely, “absolute position,” “relative position,” and “shape” of each element, are discussed on the basis of the measured optical axis elongation as functions of pulse duration and fluence.