arXiv subjects

Joseph B. Geddes III

Publications and source records attributed to Joseph B. Geddes III.

4 recordsLinked to original sources

arXiv2010

Thin-Film Metamaterials called Sculptured Thin Films

Morphology and performance are conjointed attributes of metamaterials, of which sculptured thin films (STFs) are examples. STFs are assemblies of nanowires that can be fabricated from many different materials, typically via physical vapor deposition onto rotating substrates. The curvilinear--nanowire morphology of STFs is determined by the substrate motions during fabrication. The optical properties, especially, can be tailored by varying the morphology of STFs. In many cases prototype devices have been fabricated for various optical, thermal, chemical, and biological applications.

physics.optics↗

arXiv2007

When does the choice of the refractive index of a linear, homogeneous, isotropic, active, dielectric medium matter?

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 waveguide sections with perfectly conducting walls; and (iii) image formation due to flat lenses. The correct choice does matter for the half-space problem, but that problem is not realistic.

physics.optics↗

arXiv2007

On the refractive index for a nonmagnetic two-component medium: resolution of a controversy

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 frequency domain, the deflection of an obliquely incident Gaussian beam on transmission through a dielectric slab. The dielectric medium was found to be an active medium with a negative real part for its refractive index. Thereby, a recent controversy in the scientific literature was resolved.

physics.optics↗

arXiv2006

Swamping of circular Bragg phenomenon and shaping of videopulses

We studied the durations and average speeds of videopulses transmitted through chiral sculptured thin films using a finite-difference algorithm. The chiral STF was either linear or possessed an intensity-dependent permittivity. Videopulse durations tended to decrease with increasing carrier wavelength and to increase, for given carrier wavelength and polarization state, when the chiral STF was nonlinear with intensity-dependent permittivity. The rate of decrease in durations with wavelength was less than that for longer-duration pulses. The effect of the circular Bragg phenomenon was swamped by the wide bandwidth possessed by videopulses. Two measures of videopulse average speed did not change much with carrier wavelength, and decreased slightly, for a given carrier wavelength and polarization state, in the nonlinear case. The other measure of average speed tended to increase with increasing carrier wavelength, and decrease, for a given carrier wavelength and polarization state, in the nonlinear case.

physics.optics↗