Miriam Deutsch

Single-domain spectroscopy of self-assembled photonic crystals

We show how optical microscopy can be used to study the optical properties of a single crystalline domain in a self-assembled photonic crystal. By measuring spatially resolved reflection and emission spectra from a synthetic opal, inhomogeneities due to averaging over inherent disorder can be avoided. From “defect-free” reflection and emission spectra, the intrinsic photonic band structure can be extracted and inhibition of spontaneous emission can be verified.

Conjugated-polymer photonic crystals

Three-dimensional photonic crystals made from an organic semiconductor—poly(p-phenylenevinylene) (PPV)—are studied here. Their synthesis (via colloidal assembly), physical appearance, and optical properties are investigated. The Figure shows optical micrographs of a polished PPV photonic crystal under ultraviolet (top) and white (bottom) light illumination, indicating fluorescence and optical diffraction, respectively (see also cover).

Curvature-induced radiation of surface plasmon polaritons propagating around bends

We present a theoretical study of the curvature-induced radiation of surface plasmon polaritons propagating around bends at metal-dielectric interfaces. We explain qualitatively how the curvature leads to distortion of the phase front, causing the fields to radiate energy away from the metal-dielectric interface. We then quantify, both analytically and numerically, radiation losses and energy transmission efficiencies of surface plasmon polaritons propagating around bends with varying radii as well as sign of curvature.

Surface plasmon polariton propagation around bends at a metal–dielectric interface

A short-wavelength analysis for the transmission coefficients of surface plasmon polaritons around a finite-radius metallic bend shows lower losses than on flat surfaces may occur. The maximum transmittance depends non-monotonically on the bend radius

Plasmon-assisted transparency in metal-dielectric microspheres.

We present a theoretical analysis of light scattering from a layered metal-dielectric microsphere. The system consists of two spherical resonators coupled through concentric embedding. Solving for the modes of this system, we find that near an avoided crossing the scattering cross section is dramatically suppressed, exhibiting a tunable optical transparency. Similar to electromagnetically induced transparency, this phenomenon is associated with a large group delay, which in our system is manifest as flat azimuthal dispersion.

Coherent light scattering from semicontinuous silver nanoshells near the percolation threshold.

We report on measurements of visible extinction spectra of semicontinuous silver nanoshells grown on colloidal silica spheres. We find that thin, fractal shells below the percolation threshold exhibit geometrically tunable plasmon resonances. A modified scaling theory approach is used to model the dielectric response of such shells, which is then utilized to obtain the extinction cross section in a retarded Mie scattering formalism. We show that such spherical resonators support unique plasmon dynamics: in the visible there is a new regime of coherently driven cluster-localized plasmons, while crossover to homogeneous response in the infrared predicts a delocalized shell plasmon.

Enhanced surface plasmon resonance absorption in metal-dielectric-metal layered microspheres

We present a theoretical study of the dispersion relation of surface-plasmon resonances of mesoscopic metal-dielectric-metal microspheres. By analyzing the solutions to Maxwells equations, we obtain a simple geometric condition for which the system exhibits a band of surface-plasmon modes whose resonant frequencies are weakly dependent on the multipole number. Using a modified Mie calculation, we find that a large number of modes belonging to this flat-dispersion band can be excited simultaneously by a plane wave, thus enhancing the absorption cross section. We demonstrate that the enhanced absorption peak of the sphere is geometrically tunable over the entire visible range.

Macroscopically ordered thin films of an organic salt grown by low-pressure organic vapor-phase deposition

Abstract We demonstrate the process of low-pressure organic vapor-phase deposition (LP-OVPD) for the growth of crystalline thin films of the organic charge-transfer salt 4′-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) on amorphous TiO 2 substrates. LP-OVPD grown films exhibit polycrystallinity with long-range structural ordering limited only by substrate size. Film surface coverage and macroscopic ordering are strongly determined by the preparation of the TiO 2 surface prior to growth. The morphology and ordering of the films are also found to depend on the deposition temperature and the composition of the precursor molecules. These results suggest that LP-OVPD films are of sufficient quality for use in optical waveguide and related photonic devices.

Conductivity and scaling properties of chemically grown granular silver films

We address room-temperature conductivities of chemically grown silver films. Disordered, granular silver films are grown using a modified Tollens reaction. Thick, polycrystalline films are transparent at visible wavelengths, with crystallinity similar to that of silver powders. The measured conductivities are close to those measured by I. V. Antonets, L. N. Kotov, S. V. Nekipelov, and Ye. A. Golubev, Tech. Phys. 49, 306 (2004) in amorphous silver films, however the thickness where bulk conductivity is reached is anomalously high. While measured resistance values do not obey a scaling relation in thickness, accounting for the films’ structural porosity through geometrical rescaling of the thickness leads to emergence of the well-known percolation power-law scaling, albeit that of two-dimensional percolating films.

Metamaterial coatings for broadband asymmetric mirrors

We report the design and fabrication of nanostructured metal-dielectric mirrors with high reflectance asymmetries in the visible spectral range. Applying dispersion engineering principles to model a broadband and large reflectance asymmetry, we obtain a dielectric function for this metamaterial, closely resembling the effective permittivity of disordered metal-dielectric nanocomposites. Coatings realized by using disordered nanocrystalline silver films on glass substrates confirm the theoretical predictions, exhibiting symmetric transmittance, accompanied by large broadband reflectance asymmetries.