On-chip natural assembly of silicon photonic bandgap crystals

Abstract

Photonic bandgap crystals can reflect light for any direction of propagation in specific wavelength ranges. This property, which can be used to confine, manipulate and guide photons, should allow the creation of all-optical integrated circuits. To achieve this goal, conventional semiconductor nanofabrication techniques have been adapted to make photonic crystals. A potentially simpler and cheaper approach for creating three-dimensional periodic structures is the natural assembly of colloidal microspheres. However, this approach yields irregular, polycrystalline photonic crystals that are difficult to incorporate into a device. More importantly, it leads to many structural defects that can destroy the photonic bandgap. Here we show that by assembling a thin layer of colloidal spheres on a silicon substrate, we can obtain planar, single-crystalline silicon photonic crystals that have defect densities sufficiently low that the bandgap survives. As expected from theory, we observe unity reflectance in two crystalline directions of our photonic crystals around a wavelength of 1.3 micrometres. We also show that additional fabrication steps, intentional doping and patterning, can be performed, so demonstrating the potential for specific device applications.

Transport of particles in liquid crystals

“…Self-assembly of ordered structures, although offering a broad technological platform 8 , often requires a guiding support of quasi 2D templates (substrates) 100,101 . The development of practical strategies for the assembly of 3D arrays remains an unsolved problem 102 .…”

Tunable structural color in organisms and photonic materials for design of bioinspired materials

“…The crystalline diffraction from opal has been studied for photonic applications [50,51], and one of the milestone achievements was the design of an inverse silicone opal structure with a full band gap by the North American NEC group [52]. In addition to 3D photonic crystals, the structural color of colloidal crystals has been attracting increasing attention.…”

Designing synthetic optical media: photonic crystals

“…2, comprising an alternating sequence of 2D-periodic arrays of dielectric rods and holes, connecting into a diamond topology [14]; photographs of actual fabricated structures in progress [16] are shown at right. Many other 3D crystal fabrication strategies have also been employed, from colloidal self-assembly [17] to holography [18].…”