We report a minute-long, single step, room temperature and spontaneous route to complex 3-D optical lattices and their corresponding waveguide architectures. The method exploits the instability and spontaneous filamentation of broad light beams propagating through a photopolymerisable medium and in this way, combines the ease and elegance of self-organisation with the precision and directionality that characterise beam-directed lithography. We found that when launched into a photopolymer, an orthogonal pair of white incandescent beams spontaneously divided into light filaments that self-organised into a hexagonal lattice. When made to intersect, the orthogonal hexagonal lattices generated a 3-D optical lattice with BCC symmetry and when made to interleave, yielded a lattice with the woodpile arrangement. These optical lattices permanently inscribed microstructures composed of thousands of discrete cylindrical, multimode and polychromatic waveguides. The structural lattices spanned a volume of ≅1000 mm3, at least an order of magnitude greater than volumes that are typically constructed through lithography or assembled through self-organisation processes. The densely packed and multidirectional waveguide lattices could serve as fundamentally new and remarkably inexpensive devices with highly efficient, angle-independent light collection and guiding capability. As a result, they hold significant potential to improve the light-harnessing capabilities of photovoltaic devices and separately, to function as nonlinear photonic crystals.
