Laser polymerization of Photonic Crystals for collimation of beams at visible wavelengths

Three-dimensional photonic crystals with woodpile structure are demonstrated to exhibit collimation of light beams behind the photonic structure. Woodpile structure photonic crystals with longitudinal modulation periods in a range of 7.4 - 7.8 μm, and transverse periods of 1 μm were fabricated using laser multi-photon polymerization technique in a negative-tone photoresist. As expected from theoretical predictions, the beams propagating along the axis of period variation collimate behind the crystal, which is a first experimental observation of the phenomenon.