Sean Wong

Towards the synthetic all-optical computer: science fiction or reality?

The global race for the optically integrated photonic chip is driven by the prospective that miniaturization of optical devices and enhanced chip functionality may revolutionize the manufacture of optical circuits, and the futuristic dream of the all-optical computer may come true. The aim of this article is to take a brief yet critical look at some developments in microsphere self-assembly of colloidal photonic crystals and their technological potential from the perspective of research results that have recently emerged from our materials chemistry group. The focus of the discussion centers on the provocative vision of the “colloidal photonic crystal micropolis”, Fig. 1, which depicts the direction in which the colloidal photonic crystal research of our materials chemistry group is heading. It is intended to bring to the forefront the pointed question of whether the most recent versions of colloidal photonic crystals and their integration on chips, developed in our laboratory, can rise to the stringent specifications of structural perfection and optical quality, functionality and complexity that will be demanded for photonic crystal optical devices and optical circuits touted for next generation all-optical chip and telecommunication technologies.

Tungsten inverse opals: The influence of absorption on the photonic band structure in the visible spectral region

We fabricate and characterize tungsten inverse opals for the visible and near-infrared spectral region. The influence of absorption in this spectral region and the resulting breakdown of the bandstructure are experimentally investigated in detail

Measurement of group velocity dispersion for finite size three-dimensional photonic crystals in the near-infrared spectral region

We measure group delay and group velocity dispersion of silica colloidal photonic crystals in the near-infrared with white light interferometry. While group delay and group velocity dispersion increase with sample thickness, scattering on sample imperfections is found to counteract this development, resulting in group delays lower than theoretically expected. For thin photonic crystals, group velocity dispersion imposed by Fabry–Perot oscillations is as strong as the one resulting from the periodicity. Group velocity dispersions as high as 30ps2m−1 are observed. All measurements are in good quantitative agreement with numerical calculations.

Phase-matched nondegenerate four-wave mixing in one-dimensional photonic crystals

The authors report on nondegenerate four-wave mixing in the near infrared using a one-dimensional chalcogenide-glass based photonic crystal. For 76 lattice constants, they find a 3.5-fold enhancement of the mixing signal with respect to the optimum-thickness bulk chalcogenide film. The key is the ability to tailor the dispersion relation of light in the photonic crystal, allowing for phase matching. Numerical calculations agree well with the experiments.

F2-laser digital etching of colloidal photonic crystals

We report on digital etching of silica colloidal photonic crystals by employing a pulsed deep-ultraviolet F2 laser at 157nm wavelength. When the laser fluence is above a microsphere-size-dependent threshold and within an appropriate fluence window, colloidal crystals can be etched in a digitized fashion, whereby a single microsphere layer can be removed upon exposure to a single laser pulse. Alternatively, single spheres or lines of spheres can be selectively ejected by patterning the laser beam. The results demonstrate a fast, noncontact, straightforward, and cost-effective approach for engineering extrinsic defects into colloidal photonic crystals.

Er doped As 2 S 3 photoresist for 3-D direct laser fabrication of 3-D nanostructures

We present a novel high-index-of-refraction (2.45) photoresist material based on erbium doped arsenic trisulfide. It shows room temperature photoluminescence at 1.5 microns wavelength, and can directly be used for direct laser writing.

Chiral 3D Photonic Crystals as Compact Optical Isolators

We present a novel photonic heterostructure based on chiral 3D photonic crystals allowing for non-reciprocal transmission of light. We fabricate various corresponding structures by means of direct laser writing.

Phase-matched non-degenerate four-wave mixing in one-dimensional photonic crystals

We report on non-degenerate four-wave mixing in the near-infrared using a 76 layer thick one-dimensional chalcogenide-glass based photonic crystal. A 3.5-fold enhancement of the mixing signal with respect to the optimum-thickness bulk film is observed.

Direct laser writing of three-dimensional photonic crystals in high index of refraction chalcogenide glasses

We present a two-step method for the direct fabrication of functional three-dimensional photonic crystals in high index of refraction (n=2.45) arsenic-sulphur based thin films. Complete fabrication cycles can be as short as a few hours.