We have theoretically investigated wave propagation in nonreciprocal photonic crystals (PC), which break simultaneously space-inversion and time-reversal symmetries. We identify a remarkable set of properties that are consequences of simply imposing the two symmetry constraints (independent of material choices, dimensionality, etc.). The model material system that we have investigated is a 1D periodic, lossless dielectric helical medium with magnetooptic activity for which we obtained both analytic and numerical solutions of the dispersion relations. We show that nonreciprocal PC display indirect photonic band gaps (band edges are not aligned in k-space, by analogy with the electronic case) even in the 1D case. Furthermore, we find that these PC support backward wave eigenmodes (opposite group and phase velocities). By analyzing the isofrequency contour diagrams, we show that it is also possible to obtain negative refraction at the interface between air and the photonic crystal, that nonlinearities of the photonic bands allow for superprism effects which differ from the known case by being unidirectional (i.e. not present if the light path is reversed), and that the propagation direction of light waves inside the nonreciprocal PC can be laterally deflected by perpendicular magnetic fields.
The use of virus nanoparticles, specifically Chilo and Wiseana Invertebrate Iridovirus, as building blocks for iridescent nanoparticle assemblies and core substrates in the fabrication of metallodielectric nanostructures is discussed. Virus particles are assembled in vitro, yielding films and monoliths with optical iridescence arising from multiple Bragg scattering from close packed crystalline structures of the iridovirus. Bulk viral assemblies are prepared by centrifugation followed by the addition of glutaraldehyde, a cross-linking agent. Long range assemblies were prepared by employing a cell design that forced virus assembly within a confined geometry followed by cross-linking. In addition to these assemblies core-shell particles were created from the same virus. A gold shell is assembled around the viral core by attaching small gold nanoparticles to the virus surface by means of the inherent chemical functionality found within the protein cage structure of the viral capsid. These gold nanoparticles act as nucleation sites for electroless deposition of gold ions from solution. UV/Vis spectroscopy and electron microscopy, were used to verify the creation of the virus assemblages. The optical extinction spectra of the metallo-viral complex were compared to Mie scattering theory and found to be in quantitative agreement. These investigations demonstrate that direct harvesting of biological structures, rather than biochemical modification of protein sequences, is a viable route to create unique, optically active materials.
We present a combined analysis on the creation and fabrication of three-dimensional bicontinuous photonic crystals with large complete gaps based on the modulation of the dielectric material along principal directions and its relation to the interference lithography technique.
Preferential sequestering of surface modified metal/semiconductor nanocrystals within microphase separated block copolymer domains holds the promise for engineering large-scale polymer based photonic materials. In my talk I want to review block copolymers as a material platform for photonic crystal engineering as well as the prospects of metallodielectric photonic materials based on metal nanocrystal/block copolymer composites. The effect of metal nanocrystal additives on the optical properties of the composite is found to be determined by: (1) changes in the optical properties of individual nanocrystals due to the spatial confinement of the free electrons by the crystal boundary and (2) by collective effects resulting from the particle size-dependent morphology of the nanocrystals within the polymer domains. The particle core size, the polymer domain spacing as well as the particle surface chemistry are shown to determine three distinct morphological types in particle/block copolymer composites. A detailed comparison between morphological studies and theoretical predictions will be presented that aim to better understand and control morphologies of structured cluster matter in order to tailor optical and mechanical properties of new photonic materials.
The investigation of the chemistry and physics of thin films has had a considerable impact on the fields of optics, microelectronics, coating technology, and imaging. Of the experimental work reported in the literature, films of one or two layers have been investigated. Modeling the waveguide properties of these films is straight forward and easily done. Of further interest are polymer laminates of several layers as well as polymer films with concentration gradients. As part of a larger overall effort to study multilayer film structures, computational models of optical waveguides of as many as 100 layers have been developed. With these models, it is possible to observe the changes in the distribution of the optical field intensity within the waveguide, and thus the resulting Raman intensity, by varying the number of layers, the refractive indices and thicknesses of each layer, and the wavelength. This has led to some interesting insights into the design of planar optical waveguides for spectroscopy.
Conference Committee Involvement (1)
Organic and Hybrid Materials for Nanophotonics
4 August 2003 | San Diego, California, United States