In this paper we report the superconducting quantum interference device (SQUID) and magnetic force microscope (MFM) measurements of magnetic multilayer nanoscale antidot samples. The systems used consist of Fe(60 Å)/Ni(90 Å)/Fe(60 Å) (FeNiFe) multilayer antidots with hexagonal lattice fabricated on nanochannel glass (NCG) substrates with antidot diameters of 260, 362, 530, and 800 nm. The results indicate that the domain structure is commensurate with the holes due to the pinning effect of the antidots. This pinning effect is inversely proportional to the diameter of the antidots. The field dependent MFM data show that the hexagonal antidot lattice induces a weak anisotropy with the magnetic easy axis along the nearest neighbor direction. The unit cell in the antidot arrays could be used for data storage.

We performed superconducting quantum interference devices and magnetic force microscopy (MFM) measurements on magnetic multilayer Co(60 Å)/Ni(90 Å)/Co(60 Å) nanoscale antidot samples. The antidot samples were fabricated on nanochannel glass substrates with different antidot diameters and the antidots ordered as a two dimensional hexagonal lattice structure. The results indicate that a self-organized domain structure is formed due to the pinning effect of the antidots. The strong uniaxial anisotropy of Co suppresses the shape anisotropy of the antidots and results in an uncommon domain structure. The field dependent MFM data reveal a reversal of magnetization.

The authors demonstrate the fabrication of suspended photonic crystal membranes in GaN films deposited on Si(111). The photonic crystal patterns fabricated in these membranes consisted of triangular arrays of holes having diameters in the range of 70–175nm, with a lattice spacing of 200–500nm. The patterns included optical cavity structures (groups of missing holes), which are predicted to exhibit resonances in the visible to near-IR spectral region. Such suspended photonic crystal membranes may serve as the basis for efficient wavelength-scale GaN-based light emitters monolithically integrated with Si.

We demonstrate that the spectrum of an asymmetrical photonic crystal slab has regions of vanishing transmission. Measurements are performed on GaN photonic crystal slabs consisting of twodimensional triangular lattices of holes on sapphire substrates.

A number of applications require deposition of thick, high-quality AlN films with low stress on Si substrates. Conventional high-temperature MOCVD growth produced an AlN film that exhibited cracking for a film thickness greater than 300nm due to the large tensile stress generated during the growth process. Alternative methods, including the introduction of low-temperature AlN interlayers, were developed to control the strain developed during MOCVD growth of thick AlN on Si. Additionally, an alternating sequence of AlN and AlGaN—with up to 70% AlN—in a superlattice structure was found to decrease cracking in the films. Structures with thin crack-free GaN cap layers were demonstrated.

We have developed growth techniques for GaN-based multilayer films suitable for low-loss optical waveguides, as well as precision patterning for integrated optics and photonic crystal structures with sub-100 nm critical features.

High density patterns of holes in metalorganic chemical vapor deposition grown GaN films on sapphire have been fabricated by inductively coupled plasma etching using a nickel mask. Pattern transfer from the e-beam lithographically patterned resist to the nickel etch mask was accomplished by ion beam milling. A Cl2–BCl3 inductively coupled plasma was used to anisotropically etch patterns of 200–250-nm-diam holes with 300nm center-to-center spacing through the entire thickness of a 265-nm- and a 300-nm-thick GaN film. This work demonstrates a pattern transfer technique to Ni by ion beam milling and Ni as a durable etch mask under a chlorine environment for high density patterning of GaN films.

We demonstrate that guided resonant modes can be readily observed in asymmetrical photonic crystal slabs on high-index substrates. In spite of the high radiative loss associated with all optical modes in these cases, the guided resonant modes are found to give rise to strong high-Q features in the transmission spectra. Since these photonic crystal structures are far more robust and easier to fabricate than the free-standing photonic crystal membranes used in previous studies of guided resonant modes, detailed studies of relevant optical phenomena and the implementation of proposed applications are greatly simplified.

Iron nanoparticles were synthesized in situ within the channels of a microchannel glass by differentially pumping across the plate in conjunction with plasma enhanced chemical vapor deposition. The microchannel glass was mounted on a custom designed differentially pumped sample holder, which produced 10 Torr of differential pressure across the 5 μm channels. The iron precursor was ferrocene [(C5H5)2–Fe]. The composition and structure of the nanoparticles was determined by electron diffraction to be Fe3O4, where oxidation of the nanoparticles occurred upon exposure to air. Transmission electron microscopy revealed the formation of nanoparticles ranging in size from 150 to 960 nm, which are formed from smaller nanoparticles on the order of 5–10 nm. The large nanoparticles (150–960 nm) grow independently of one another and are largely freestanding within the channels, i.e., they are not highly attached to the channel walls or agglomerated. The magnetic signature of the large nanoparticles is consistent with ferrimagnetic Fe3O4. The magnetic hysteresis loops of the particles are reminiscent of superparamagnetic behavior, which would suggest that the magnetic coupling between the 5 and 10 nm nanoparticles is weak. A model for nanoparticle formation based on plasma suspension of the Fe nanoparticles inside the glass channels is proposed.

Propagation of electromagnetic waves through a two-dimensional triangular lattice has been studied for different values of refractive index contrast between the constituent dielectrics, and for angles of incidence both in and out of the plane of periodicity. Transmission results have been obtained both experimentally and with the transfer matrix technique, and good agreement has been found between the two. Comparison with band structure calculations has also been made.

We demonstrate high-pass optical filters with cutoffs in the 0.3-10-micron spectral region. These filters consist of uniform arrays of hollow metallic waveguides, obtained by coating wafers of the previously developed channel-glass (CG) materials with a thin metal film. In these filters the channel diameter controls the cutoff frequency, the channel length controls the sharpness of the cutoff, and the channel density determines the transmission efficiency at cutoff. All of these parameters can be controlled in the CG starting material. The properties of the metal coatings that influence the filter properties are also discussed. Cutoff wavelengths near 300 nm have been achieved to date by using CG materials with submicrometer channel diameters. At all channel diameters, the transmission spectra include a peak just above the cutoff wavelength, where the transmission value can exceed that expected on the basis of the geometrical open area of the CG structure.

Summary form only given. Photonic crystals are nanostructured materials that possess a periodic modulation of the dielectric constant. We have fabricated two-dimensional (2D) triangular photonic crystals in which one of the elements is a phthalocyanine (Pc) dye. These Pc's have a wavelength dependent absorption and large nonlinear absorption and nonlinear refraction coefficients. Thus, in our new photonic crystal materials, there is a wavelength and fluence dependent modulation in both the real and imaginary part of the dielectric constant. We investigate the optical properties of such photonic crystal materials and their potential for optical limiting applications.

We have investigated the visible-region transmission spectra of light propagating in directions which lie outside the array plane of a two-dimensional photonic crystal. These photonic crystals consist of arrays of glass rods inside a glass matrix, with periodicities comparable to the wavelengths of interest. When the propagation direction is within the array plane, attenuations corresponding to the Brillouin-zone boundaries are observed, while for out-of-plane propagation all attenuation features shift to shorter wavelengths. interesting polarization-dependent effects appear for out-of-plane propagation.

Two-dimensional photonic band-structure effects have been observed in the visible and near-uv regions, between 350 and 800 nm. These effects appear in all-solid-state arrays of glass cylinders in a glass matrix. The arrays have center-to-center nearest-neighbor separations between 0.188 and 0.278 μm, perfect long-range order, and low refractive index contrast. For light propagating perpendicular to the cylinder axes, very narrow attenuations appear in the transmission spectra as a result of the photonic band structure. The positions of these attenuations are determined by the periodicity, composition, and symmetry of the arrays.

We describe the fabrication and optical transmission of two-dimensional periodic dielectric structures with photonic band gaps in the near infrared. The structures consist of triangular arrays of air cylinders embedded in a glass matrix, with center-to-center nearest-neighbor separations between 1.08 and 0.73 microm. The band gaps corresponding to the first Brillouin zone's boundaries occur at wavelengths between 2.5 and 1.1 microm. For each array size, the band gaps along the two high-symmetry propagation directions are spectrally overlapped for light polarized perpendicular to the cylinder axes. The observed positions, widths, and polarization dependence of the band gaps are in good agreement with theoretical calculations.

We demonstrate that two-dimensional periodic dielectric structures with low index contrast give rise to remarkable photonic band-structure effects. Our structures consist of triangular arrays of glass cylinders embedded in a matrix composed of a different glass, having center-to-center nearest-neighbor separations from 1.08 mu m to 0.54 mu m. The indices of refraction of the two glasses differ by less than 0.02 in the relevant spectral region. The attenuation features corresponding to the boundaries of the first Brillouin zone appear in the near-infrared, at photon energies between 0.4 eV and 0.9 eV.

The photoluminescence (PL) of 1–2 monolayers (ML) of C60 adsorbed on cold-deposited Ag and In surfaces is strongly quenched by the metal-C60 interaction. However, similar to the case of the Raman spectra of C60 on the same surfaces, the PL intensity increases substantially upon annealing of the surfaces of 300 K. Changes in the PL spectrum indicate that the metal-C60 interaction, which includes charge transfer from the surface to the adsorbed C60, perturbs the first C60 ML more strongly than the second. We attribute these effects to the introduction of nonradiative deexcitation channels involving electronic states near the metal's Fermi level.

Enhanced Raman spectra of C60 monolayers adsorbed on continuous cold-deposited silver and indium surfaces are reported; no enhancement is observed on dielectric surfaces. Surprisingly, this enhancement of the spectra of C60 on Ag and In increases significantly as the surfaces are annealed towards room temperature; such annealed surfaces do not exhibit surface-enhanced Raman scattering for other adsorbates, such as benzene. We suggest that this unusual enhancement results from a resonant Raman process involving the metal-C60 interaction, which includes electron transfer to C60. The interaction also modifies the spectral line shapes of adsorbed C60.

The infrared- and Raman-active vibrational modes of ${\mathrm{C}}_{60}$ were measured in the various structural states of ${\mathrm{RbC}}_{60}$. According to earlier studies, ${\mathrm{RbC}}_{60}$ has an fcc structure at temperatures above \ensuremath{\sim}100 \ifmmode^\circ\else\textdegree\fi{}C, a linear chain polymer orthorhombic structure when slowly cooled, and an as yet undetermined structure when very rapidly cooled (``quenched''). We show that the spectra obtained in the polymer state are consistent with each ${\mathrm{C}}_{60}$ molecule having bonds to two diametrically opposite neighbors. In the quenched state, we find evidence for further symmetry breaking, implying a lower symmetry structure than the polymer state. The spectroscopic data of the quenched phase are shown to be consistent with ${\mathrm{Rb}}_{2}$(${\mathrm{C}}_{60}$${)}_{2}$, a dimerization of ${\mathrm{C}}_{60}$.