Joseph B. Geddes

Learn More
The human eye is a remarkable imaging device, with many attractive design features. Prominent among these is a hemispherical detector geometry, similar to that found in many other biological systems, that enables a wide field of view and low aberrations with simple, few-component imaging optics. This type of configuration is extremely difficult to achieve(More)
The high natural abundance of silicon, together with its excellent reliability and good efficiency in solar cells, suggest its continued use in production of solar energy, on massive scales, for the foreseeable future. Although organics, nanocrystals, nanowires and other new materials hold significant promise, many opportunities continue to exist for(More)
Spatially overlapping plates in tiled configurations represent designs that are observed widely in nature (e.g., fish and snake scales) and man-made systems (e.g., shingled roofs) alike. This imbricate architecture offers fault-tolerant, multifunctional capabilities, in layouts that can provide mechanical flexibility even with full, 100% areal coverages of(More)
The refractive index of a dielectric medium comprising both passive and inverted components in its permittivity was determined using two methods: (i) in the time domain, a finite–difference algorithm to compute the frequency–domain reflectance from reflection data for a pulsed plane wave that is normally incident on a dielectric half–space, and (ii) in the(More)
Control of spontaneous emission (SE) is central to many applications involved with photon management including light emitting sources, [ 1–3 ] solar energy [ 4 , 5 ] and quantum information processing. [ 6 , 7 ] For example, control of the direction of SE may facilitate more effi cient light extraction in optical display devices. Spectral redistribution of(More)
The durations and average speeds of ultrashort optical pulses transmitted through chiral sculptured thin films (STFs) were calculated using a finite–difference time–domain algorithm. Chiral STFs are a class of nanoengineered materials whose microstructure comprises parallel helicoidal nanowires grown normal to a substrate. The nanowires are ∼10–300 nm in(More)
X-ray computed tomography is used to reconstruct the 3D structure of a polymeric photonic crystal. The reconstructed structure is compared to the structure predicted by a model. This analysis provides means to better understand deformations that occur during holographic fabrication of photonic crystals.
Two choices are possible for the refractive index of a linear, homogeneous, isotropic, active, dielectric material. Either of the choices is adequate for obtaining frequency-domain solutions for (i) scattering by slabs, spheres, and other objects of bounded extent; (ii) guided--wave propagation in homogeneously filled, cross-sectionally uniform, straight(More)