A finite thickness slab of a metamaterial having a refractive index close to n = -1, can be used for sub-wavelength scale
imaging. In the image domain, the measured fields contain evanescent wave contributions from subwavelength scale
features in the object but these have to be related to the intrinsic parameters describing the scatterer such as refractive
index or permittivity. For weak scatterers there can be a simple relationship between the field distribution and the
permittivity profile. However for strong (multiple) scatterers and, more importantly, for objects for which
subwavelength features contribute to the scattered (near) field, there is no simple relationship between the measured data
and the permittivity profile. This is a significant inverse scattering problem for which no immediate solution exists and
given the metamaterial slab’s limitations one cannot assume that either angle or wavelength diversity will be available to
apply an inverse scattering algorithm. We consider wavelength diversity in this paper to acquire the measured data
necessary to estimate a superresolved solution to the inverse scattering problem.
We investigate superresolution imaging using negative index metamaterials. Measurement of subwavelength scale
features in the image domain is tedious and compressive sampling techniques are considered to alleviate this problem. A single detector (c.f. a single pixel camera geometry) is considered from which a high resolution image can be computed, which makes use of structured illumination for coding.
In order to better understand how to improve the performance of a superlens, structural and geometrical arrangements of
meta-atoms are investigated. Each meta-atom (i.e. the unit element composing a metamaterial) in our study is an
asymmetric 3D "S"-shaped resonator. This structure radiates an enhanced scattered field at several possible resonant
frequencies, some of which are out of phase with the incident wave. We retrieve the effective parameters of different
metamaterials and discuss the role of meta-atom symmetries and dimensions in affecting the effective refractive index of
a metamaterial slab. Relative locations and orientations of individual meta-atoms are investigated to provide desired
properties with low loss despite the inevitable finite size of each meta-atom. The results presented provide insights for
designing superlenses, resonant antennas, and other potential applications.
The Talbot effect refers to the self-imaging property of periodic structures illuminated by collimated, coherent light.
Complex periodic and quasi-periodic irradiance distributions are formed in three-dimensional (3-D) space near the
gratings through diffraction and interference. A wide variety of novel irradiance distributions can be synthesized through
design of the grating structures. These irradiance distributions can be converted into dielectric structures through
exposure of photosensitive materials and subsequent processing or, alternately, can serve as inspiration for photonic
crystals to be fabricated through other techniques. In this paper, we explore the dispersion properties of a rhombus lattice
photonic crystal structure inspired by the fractional Talbot effect. These "Talbot crystals" are used to demonstrate
potential for broadband "all-angle" self-collimation for waveguide and optical multiplexing applications. Additional
directions for future research will also be discussed.
Interference in the Fresnel regime of periodic structures creates a wide variety of intricate diffraction patterns. The diffraction patterns from both amplitude and phase gratings can bear a strong resemblance to the grating itself, or have much more complex structures. In this paper, we discuss a general approach for using interference patterns from amplitude gratings for lithographic fabrication of optical microstructures. We address the generation of the interference patterns from the standpoint of Talbot self-imaging. This approach enables the realization of complex optical structures with a single exposure in an appropriate fractional Talbot plane. Design approaches are discussed, and both theoretical and experimental results are presented.