Accession Number:

ADA591236

Title:

Subwavelength Sensing Using Nonlinear Feedback in a Wave-Chaotic Cavity

Descriptive Note:

Doctoral thesis

Corporate Author:

DUKE UNIV DURHAM NC DEPT OF PHYSICS

Personal Author(s):

Report Date:

2013-01-01

Pagination or Media Count:

293.0

Abstract:

Typical imaging systems rely on the interactions of matter with electromagnetic radiation which can lead to scattered waves that are radiated away from the imaging area. The goal such an imaging device is to collect these radiated waves and focus them onto a measurement detector that is sensitive to the waves properties such as wavelength or color and intensity. The detectors measurements of the scattered fields are then used to reconstruct spatial information about the original matter such as its shape or location. However, when a scattered wave is collected by the imaging device, it diffracts and interferes with itself. The resulting interference pattern can blur spatial information of the reconstructed image. This leads to a so-called diffraction limit, which describes the minimum sizes of spatial features on a scatterer that can be resolved using conventional imaging techniques. The diffraction limit scales with the wavelength of the illuminating field, where the limit for conventional imaging with visible light is approximately 200 nm. Investigating subwavelength objects requires more advanced measurement techniques, and improving the resolving capabilities of imaging devices continues to be an active area of research. Here, I describe a new sensing technique for resolving the position of a subwavelength scatterer with vastly subwavelength resolution . My approach combines two separate fields of scientific inquiry time-delayed nonlinear feedback and wave chaos. In typical time-delayed nonlinear feedback systems, the output of a nonlinear device is delayed and fed back to its input. In my experiment, the output of a radio-frequency 15 cm nonlinear circuit is injected into a complex scattering environment known as a wave-chaotic cavity.

Subject Categories:

  • Radiofrequency Wave Propagation

Distribution Statement:

APPROVED FOR PUBLIC RELEASE