The focus of this present work is concerned with a novel and facile method for obtaining colored Ag nanoparticle films using a sulfide as a coloring agent. The Ag nanoparticle films change their colors depending on the dipping time in a solution of a sulfide and the dipping time is at most on the second time scale. The color of the films, initially sliver (shiny white), changes to shiny yellow, red, and blue. Our scanning electron microscopy studies indicate that the color of the Ag nanoparticle films depend on the particle size of the Ag nanoparticle films.

Conventional photonic crystals exhibit low-lying full band gaps for the dielectric contrast smaller than 15. As the dielectric contrast increases, the band gap patterns change characteristics and exhibit interesting properties. In particular, the dispersion curves near the band gap region become concentrated to the middle band frequencies and exhibit an overall red shift in frequency. For a dielectric column photonic crystal made of a hexagonal lattice of circular cylinders, the maximum full band gap was found at the dielectric contrast as high as 27.5, which is attainable by using ceramics materials. The gap opens at high-lying bands, has simultaneous TM and TE band edges, and exhibit flattened dispersion curves near the band edges.

Electromagnetic mode localization within photonic bandgap (PBG) crystals has been evidenced by external measurement of enhanced optical emission from quantum dots or photoemissive polymers that are placed within the structure. In this paper wavelength is decreased and photonic crystal dimensions increased to allow insertion of a loop probe in the PBG to directly measure volumetric electromagnetic fields; thereby producing a volume -frequency map of field amplitude and phase within the PBG. The unit cells of the PBG are formed from arrays of Alumina strips which are supported by surrounding acrylic supports. Electromagnetic fields of single, two and three layer PBGs are predicted and these compare well with measurement.

Field localization within the PBG and transmission coefficients of the PBG, with and without electrical perturbations, are presented. Predictions assume layered unit cells formed from sections in which translational invariance along the Z-axis is assumed for zn-1 ≤ z ≤ zn for the nth section. Periodicity implies that field X dependence can be represented as a sum of Floquet modes and field solutions are found by mode matching techniques in combination with multimode cascade matrix formalism.

Transmission coefficient is measured using a focused beam, network analyzer based system and volumetric fields within the PBG are measured using a loop probe antenna inserted between Alumina strips and moved to different positions. Measurements at 1600 frequencies over the 4-18 GHz band at each of 100 positions are made. PBG fields are calibrated to probe measurements at identical positions and frequencies but absent the PBG.

Both electromagnetic model and measurement shows field localization and effective negative or zero indexes at multiple frequencies within the 4 to 18 GHz band. Volumetric field magnitudes increase by at least one order of magnitude and local field phase-frequency derivatives are negative or near zero near localization frequencies. Field localizations and transmission are sensitive to small perturbations of electrical properties or geometry. Wideband measurements of PBGs, perturbed by small cylindrical inserts placed at high field locations, allow precision measurements of an insert’s electromagnetic properties.

We report plasmon lasers with strong cavity feedback and optical confinement to 1/20th wavelength. Strong feedback arises from total internal reflection of plasmons, while confinement enhances the spontaneous emission rate by up to 18 times.