This PDF file contains the front matter associated with SPIE Proceedings Volume 6767, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

We have developed a simple method to produce large colloidal crystal films for a like-charged particles system, where particle arrays with single-crystalline-like characteristics are made by a flow-induced process. A poly-crystalline suspension was charged in a flat capillary and processed by strong shear flow. Optical characterizations for the uniform samples indicate that almost all the capillary space (several square centimeters wide and 0.1mm thick) is filled with a single-domain crystal with a fixed crystallographic orientation determined by the cell geometry. The single-domain crystal can be fixed in a self-standing hydro-gel film by polymerizing gelation agents added in the suspension. Upon gelation, the optical quality was found to be well preserved. We also show tunable characteristics of the gelled crystals in some different aspects. They can be contracted by changing the composition of the solvent. The stop-band width can be effectively expanded by adjusting the fabrication condition. These transformations can be made as single domains that should be advantageous to application purposes.

Photonic Crystals (PhCs) have been found to have exotic properties, such as the high dispersion and the slow group velocity, at different frequency range. It has also been reported that the photonic crystal can behave like a negative index material that is similar to the metallization based metamaterials composed of ring resonators and wires. It is essential to have knowledge about the effective properties of a photonic crystal to evaluate its performance. Here, we discuss a photonic crystal with air holes etched in a multilayer dielectric material. This structure can be cascaded to a three dimensional photonic crystal by simply stacking the porous multilayer film. Light is propagating perpendicularly through the multilayer film, and the transmission and reflection including both the magnitudes and the phases are obtained through numerical simulation. Effective properties along this direction, including the permittivity, the permeability and the effective refractive index, are calculated. From these basic and essential properties, other features such as dispersion, group velocity can be derived.

We report the application of a photonic crystal sensor for the components of a liquid mixture by a simple and easy technique. A closely packed colloidal crystal film is made of arrayed 202-nm PS particles and PDMS elastomer is used for filling the voids in the film. Bragg's diffraction in the visible wavelength region causes the formation of a structural color in the colloidal crystal. The structural color varies according to the solvents depending on the swelling ability of the PDMS elastomer. We can perform the quantitative analysis of the swelling phenomena by measuring Bragg's diffraction peaks. The peak shifts as a function of the mixing ratio of the solvents, i.e., methanol, ethanol, and propanol. The peak position is proportional to the solvent concentration. In the case of a water-ethanol system, there is little peak-shift up to 80 vol.% of ethanol concentration. Above this concentration, the rate of peak shift increases beyond 50 nm. A reflectance spectrometer enables the detection of the components of ethanol liquids with the volume concentration of water ranging from 0 to 10%. In this study, a commercially available optical fiber spectrometer detects the volume concentrations of water of the order of 1 vol.% in ethanol. The photonic sensor has the potential to be used in a rapid analysis method that employs a portable optical fiber spectrometer.

Morpho butterfly's metallic blue luster, which is produced from the butterfly's scale, has a mysterious feature. Since the scale does not contain a blue pigment, the origin of the coloration is attributed to a microscopic structure that can also explain its high reflectivity. However, it appears blue from wide angular range, which contradicts obviously the grating or multilayer. The mystery of the lack of multi-coloration has recently been explained with a peculiar nano-structure, and experimentally proven by fabricating the optical film by controlling the parameters in nanoscale. The reproduced Morpho-blue was found to be important from viewpoint of a wide variety of applications. However, optical properties of the fabricated film were found to contain still some differences with that of the Morpho-butterfly, although the basic characteristics of the Morpho-blue itself was reproduced. In order to make the artificial Morpho-blue closer to the natural one than the prototype, we attempted to optimize the artificial film structure by controlling fabrication parameters. In this process, optical simulations and micro-structural observations were taken in account. By comparing a series of films fabricated with different nano-patterns, optimized parameters were semi-empirically obtained. Also the relationship between the structural parameters and the optical properties was analyzed. The reflective characteristics of the optimized film were found to reproduce the optical properties more closely to the natural Morpho-blue than the prototypes.

Photo-tunable PBG composite material was prepared by infiltration of the polymer liquid crystal (LC) having azo-chromophores in a SiO₂ inverse opal structure. The SiO₂ inverse opal film infiltrated with the polymer LC reflected a light, which is called Bragg diffraction, corresponding to the periodicity as well as the refractive indices of the inverse opal structure. Linearly polarized light irradiation caused the shift of the the Bragg diffraction band to longer wavelength more than 15 nm. This is caused by the formation of uniaxially anistorpic molecular orientation of the polymer LC. The switched state was stable under interior light, and reversible switching of the reflection band can be achieved by the linearly and circularly polarized light irradiation. This photoswitching property will be suitable for various optical materials such as memory, display so on.

Incorporation of iron(0) complex into polymer-grafted silica and colloidal crystallization in organic solvent were studied. In this study, zero-valence iron complex, vinylferrocene (Vfc) and iron(0)tricarbonyl(4,4-dimethyl-1,-4-cyclohexadienyl) acrylate (Fe(0)Ac) or methacrylate (Fe(0)Me), were introduced into grafted polymer to prevent from increasing ionic strength in colloidal crystallization system. Poly(methyl methacrylate (MMA)-co-Vfc)-grafted silica never formed colloidal crystals in polar solvent, such as acetone or acetonitrile. However, increasing ferrocenyl group fraction in the polymer resulted in disturbing the crystallization. Poly(N-isopropylacrylamide (NIPAAm)-co-Vfc)-grafted silica, which was composed of mole fraction of Vfc, 1/3, afforded crystallization in ethanol over the particle fraction of 0.053. In the case of diene-Fe(0)(CO)₃/polymer-grafted silica, poly(MMA-co-Fe(0)Ac)-, poly(NIPAAm-co-Fe(0)Ac)- and poly(N.N-dimethylacrylamide (DMAAm)-co-Fe(0)Ac)-grafted silica gave colloidal crystallization in relatively low polar solvents, DMF, acetone, acetonirile and ethanol, critical volume fraction for which were in the range from 0.054 to 0.117. In the case of copolymer-grafted silica containing Fe(0)Me, poly(MMA-co-FeMe)-grafted silica crystallized in DMF, Interestingly, especially in cases of polymer-grafted silica containing Fe(0)Ac or Fe(0)Me composed of the highest mole fraction Fe(0)Me, 1/2, afforded crystallization in DMF. The iridescence color of the colloidal crystals was changed with the combination of grafted polymer and solvent. The characteristic coloration of the solution from reddish to greenish color is possibly due to absorption of blue light region by diene-Fe(0)(CO)₃ complex and Bragg deflection on colloidal crystals.

A theoretical model of a tunable Mach-Zehnder interferometer (TMZI) constructed in a 2D photonic crystal is proposed. The 2D PhC consists of a square lattice of cylindric air holes in silicon. The TMZI includes two mirrors and two splitters. Lights propagate between them employing self-collimation effect. The two interferometer branches have different path lengths. Parts of the longer branch are infiltrated with a kind of liquid crystal (LC) whose ordinary and extraordinary refractive indices are 1.522 and 1.706, respectively. The transmission spectra at two MZI output ports are in the shape of sinusoidal curves and have a uniform peak spacing 0.0017c/a in the frequency range from 0.26c/a to 0.27c/a. When the effective refractive index n_eff of the liquid crystal is increased from 1.522 to 1.706, the peaks shift to the lower frequencies over 0.0017c/a while the peak spacing is almost kept unchanged. So this TMZI can work as a tunble power splitter or an optical switch. For the central operating wavelength around 1550nm, its dimensions are only about tens of microns. So this device may be applied to photonic integrated circuits.

A modal solution approach, based on a powerful, full-vectorial, H-field based finite element method (FEM), has been used to analyze the single mode operation of a PCF and the modal solution of the fundamental space filling mode has been analyzed. The FEM with perfectly matched layer condition has been used to characterize the leakage loss of a PCF and the differential loss between the polarized modes of a PCF and as a result, the design of a single mode single polarization PCF has also been proposed.

LPG structures were fabricated on Microstructured Disordered Fibers with attenuation peaks from -16.9 to -24.5 dB in the transmission range from 1160nm and 1630nm, with an average of -20.8 dB and a standard deviation of 3.8dB. These structures were compared to LPGs fabricated previously on Random Hole Optical Fibers with the largest attenuations peaks for all modes located between 1160nm and 1630nm in the range from -9.5dB to -22.3dB with an average of -11.8dB, σ=5.2dB. Based on fabrication of long period gratings on these two different types of holey optical fibers, we have proven the feasibility of this process which may extend the possible field of application of those low cost fibers in fiber optic sensors and this has also confirmed the flexibility of the arc-discharge fabrication method for long period gratings.

In this paper, we present the numerical analyses of modal coupling properties and resonance spectral response of longperiod gratings (LPGs) in solid-core photonic crystal fibers (PCFs) with respect to their sensitivity to refractive indices of measurands in the air channels using a full-vectoral mode solver combined with frequency-domain method. The calculated results show that the wavelength resonance of a PCF-LPG can be extremely sensitive to the refractive index change. The PCF-LPG refractive index sensors, inscribed by residual stress relaxation using a scanning CO₂ laser, are also experimentally investigated in terms of resonance shift with the PCF-LPG structure filled with sodium chloride (NaCl) solutions at concentrations ranging from 0-26% (w/w). The spectral features were greatly improved by inscribing the LPG structure in PCF prefilled with water. The PCF-LPG sensors are shown to be able to detect the change of ~10^-7 refractive index unit (RIU) in the index range of 1.33 to 1.35, in a good agreement with the numerical simulation.

We have explored the use of index-guiding liquid-core photonic crystal fiber (LC-PCF) as a platform for sensing and measurements of analyte solutions of minute volume by normal and surface-enhanced Raman scattering (SERS). The index-guiding LC-PCF was fabricated by selectively sealing via fusion splicing the cladding air channels of a hollow-core PCF (HC-PCF) while leaving the center core open at both ends of the fiber. The center core of the resultant fiber was subsequently filled with water-ethanol solution mixtures at various ethanol concentrations for normal Raman scattering measurements and with water-thiocynate solutions containing Ag nanoparticle aggregates for SERS detection of thiocynate at trace concentrations. The light-guiding nature in the solution phase inside the LC-PCF allows direct and strong light-field overlap with the solution phase over the entire length of the PCF (~30 cm). This detection scheme also dramatically reduces the contribution of silica to Raman spectral background, compared with the solid-core counterpart, thus its potential interference in spectral analysis. These features attribute to ready normal Raman measurements of water, ethanol, and water (99 vol.%)-ethanol (1 vol.%) solutions as well as sensitive and reproducible SERS detection of ~10 ppb thiocynate in water, all at a volume of ~0.1 μL.

We report the progress toward a novel waveguide gas laser based on hollow-core light guiding capillaries and hollowcore photonic bandgap (PBG) fibers. Since Smith reported the first waveguide He-Ne laser at 0.633μm with a 20cm length of 430μm-diameter-bore glass-capillary-tubing in 1971, no smaller size waveguide gas laser has ever been constructed. Conventional hollow waveguide theory reveals that small bore size tubes suffer greater waveguide loss which hinders the construction of smaller size waveguide gas lasers. Hollow-core PBG fibers guide light through PBG effect that is different from grazing incidence mechanism of traditional simple hollow waveguides, and PBG fibers with a loss of below 0.5dB/m have been demonstrated at various wavelengths including 633nm. This indicates that we may construct waveguide gas lasers with such hollow-core PBG fibers. We carried out a series of experiments and succeeded in discharging gases contained within 250μm, 150μm and 50μm bore diameter hollow-core light guiding capillaries or fibers. Stable glow discharge of at least several minutes was observed for these waveguides. A flash glow was also observed from a hollow-core capillary with a diameter of ~20μm. Initial measurements of current-voltage (I-V) characteristics have been carried out for various tube sizes filled with various gases at different pressures. Theoretical IV characteristics are also presented and compared with experimental results. Discharging miniature waveguide bore tubes was found to exhibit unique characteristics that are different from the traditional larger diameter tubes.