The photonic band gap of colloidal crystal films made of polystyrene nanospheres was controlled by dry etching
technology using hyperthermal neutral beam. Vertical deposition technique was applied to prepare colloidal crystal films
with face centered cubic lattice structure using aqueous suspension of monodispersed polystyrene particles. The
pseudogap of these colloidal photonic crystals was tuned by etching the films with neutral beam, which reduces the size
of the constituent polystyrene particles. Isotropic reduction of the particles in collodial crystal films resulted in the blue
shift of stop band of the photonic band gap materials. By changing the etching time, the reflected colors of the dry-etched
colloidal crystals were successfully controlled.
Holographic lithography provides a highly compatible and facile way to fabricate multi-dimensional periodic
nanostructures. Periodic nanostructures have useful applications not only as biological substrates or catalytic supports
but also as nanophotonic devices with various photonic properties such as photonic band-gap (PBG), localized surface
plasmon resonance (LSPR) or surface enhanced Raman scattering (SERS). In combination with single refracting prism
holographic lithography and conventional photolithography, we could achieve the micrometer-scale patterns of periodic
nanostructures which can be integrated in microfluidic chip. With the help of conventional MEMS technologies, Arrays
of pyramid shape and top-cut pyramid shape microprism can be prepared. Single laser exposure step through the
microprism arrays (MPAs) can be generate multiscale patterns of 2D and 3D nanostructures. As prepared nanostructures
combined with microfluidic chip is a highly efficient optofluidic platform which is applicable to the chemical and biosensors.
Diamond-like silicon photonic crystals were fabricated by sequential chemical vapor deposition of silica and silicon on
polymer templates photopatterned by holographic lithography. The optical properties of the 3D crystals after each
processing step were measured and compared to the corresponding bandgap simulation. The core-shell morphology
formed during CVD process is approximated using two level surfaces.
Photonic crystals have now started to make the transition from basic to applied research, with new
materials systems and device results being published on a frequent basis. While a number of
photonic crystals have been made using organic materials, the lack of high index organic materials
has impeded their development. We have investigated several novel high index organic systems for
use in both 2-D and 3-D photonic crystals. 2-D photonic crystal templates were made by a rapid
multibeam interference method in the photoresist SU-8, using 532nm laser radiation. These samples,
typically on glass, were then infiltrated by a number of methods including from solution and melt, as
well through chemical vapor deposition. Solutions of a titanium precursor with a cured refractive
index of 2.1 at 633nm were infiltrated and cured in the SU-8 structure, with the infiltrant deposited by
both by spin coating and casting. The resulting structure was shown to preserve the six-fold
symmetry of the initial photonic crystal and subsequent firing at high temperature effectively
removed the SU-8 template. We have also explored the infiltration of nanoamorphous carbon into
the photonic crystals using chemical vapor deposition. This material, which is essentially a
carbon-silicon ceramic, has exceptional infrared optical properties with a refractive index > 2 for
wavelengths beyond 2 μm. The SU-8 polymer template has been shown to survive the CVD
deposition process and the resulting infiltrated structure also preserves the initial PC symmetry. A
series of metal-like PCs with a full range of properties is enabled by the ability to dope the
nanoamorphous carbon with metals that possess exceptional refractive indices in the infrared regions
of interest. We have also investigated the potential for nonlinear optical devices based upon
azobenzene copolymer infiltrated silicon PCs and demonstrate the excellent properties of this material
with respect to all-optical effects.
We fabricated two-dimensional (2D) polymeric photonic crystals with atoms stretched along a specific direction by using a double exposure with phase modulation.
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