Development of three-dimensional photonic crystals in the infrared wavelength region by micromanipulation method

We demonstrate a novel fabrication technique that has the potential to realize intricate three-dimensional photonic devices. Photonic crystals were fabricated by stacking two-dimensional photonic plates by micromanipulation. Accurate periodicity was maintained by using fiducial holes, which were prepared in the frame of photonic plates, and polystyrene microspheres as stoppers. With this method, up to two periods (eight layers) of woodpile structures with a periodicity of 1.4 μm and a pile width of 0.37 μm were fabricated. With this technique, the accurate alignment of lattice can be achieved automatically regardless of how complicated the photonic crystal structure is. Thus, this technique is suitable for fabricating complex structures. The fabricated crystals were evaluated based on their optical properties. In the measurements of transmittance, a dip appeared in the supposed wavelength region (3-5 μm), and its intensity become stronger as the number of layers increased. In the measurements of reflectance, a peak appeared at the same wavelength. These results indicate that the obtained crystals are fine enough for developing an optical stopband in infrared wavelength region.