Submicron-sized voids and void channels can be generated in a solid transparent polymer by using a tightly focused femtosecond laser induced micro-explosion method. By stacking the voids and void channels layer by layer and periodically, we can fabricate various three-dimensional (3D) photonic crystals of woodpile, face-centred-cubic, body-centred-cubic, and diamond lattice structures. The photonic bandgap effects and the defect generation in the photonic crystals have been revealed.
Fabrication of three-dimensional photonic crystals by the microexplosion techniques has recently been demonstrated by a number of groups. However, simple models which are currently used for characterizing the void-based photonic structures do not produce adequate results. Here, we suggest a new theoretical approach for analyzing the properties of the three-dimensional photonic crystals which allow to improve the results of the theoretical modeling of the photonic crystals created by the microexplosion method. In particular, we study the bandgap spectrum of the three-dimensional photonic crystals introducing a shell of a high-index material surrounding an air void in the face-centered-cubic lattice. This allows us to suggest an effective theoretical model which correlates very well with the properties of the microexplosion polymer photonic crystals produced experimentally. We also discuss some interesting effects observed in the fabricated photonic crystals which until now have not been understood due to the inadequacies of simple models.
Micron-sized void dots have been generated in a solidified resin by using ultrafast-laser driven micro-explosion method. Side view confocal images of the void dots show that the void dots are almost spherical. The diameter of the void dots can be controlled by adjusting the laser power and exposure time. Three-dimensional (3D) structures, stacked in the  lattice direction, of diamond, FCC and BCC lattices have been fabricated, respectively. Multi-order stop gaps are observed for all three different types of structures. The suppression rate of the first order gap can be up to 70% for diamond and FCC structures. The angle dependence of the bandgap properties of a diamond structure reveals that the observed first order gap shifts to the longer wavelength whereas the second gap shifts to the shorter wavelength as the angle of incidence increases. Such a sensitive angular dependence of the bandgap structure may find applications in photonic crystal superprisms.