Wyatt Adams

Bringing the ‘perfect lens’ into focus by near-perfect compensation of losses without gain media

In this paper, the optical properties and imaging performance of a non-ideal Pendrys negative index flat lens with a practical value for loss are studied. Analytical calculations of the optical properties of the lens are performed, and those results are used to further study the lens and corresponding imaging system numerically. An inverse filter emulating the plasmon injection scheme for loss compensation in negative index metamaterials is applied to the results from the imaging system, resulting in a perfect reconstruction of a previously unresolved image that demonstrates sub-diffraction-limited resolution.

Review of near-field optics and superlenses for sub-diffraction-limited nano-imaging

Near-field optics and superlenses for imaging beyond Abbe’s diffraction limit are reviewed. A comprehensive and contemporary background is given on scanning near-field microscopy and superlensing. Attention is brought to recent research leveraging scanning near-field optical microscopy with superlenses for new nano-imaging capabilities. Future research directions are explored for realizing the goal of low-cost and high-performance sub-diffraction-limited imaging systems.

Enhancing the Resolution of Hyperlens by the Compensation of Losses Without Gain Media

We present a method to improve the resolution of available hyperlenses in the literature. In this method, we combine the operation of hyperlens with the recently proposed plasmon injection scheme for loss compensation in metamaterials. Image of an object, which is otherwise not resolvable by the hyperlens alone, was reconstructed up to the minimum feature size of one seventh of the free-space wavelength.

Active plasmon injection scheme for subdiffraction imaging with imperfect negative index flat lens

We present an active physical implementation of the recently introduced plasmon injection loss compensation scheme for Pendry’s non-ideal negative index flat lens in the presence of realistic material losses and signal-dependent noise. In this active implementation, we propose to use a physically convolved external auxiliary source for signal amplification and suppression of the noise in the imaging system. In comparison with the previous passive implementations of the plasmon injection scheme for subdiffraction-limited imaging, where an inverse filter post-processing is used, the active implementation proposed here allows for deeper subwavelength imaging far beyond the passive post-processing scheme by extending the loss compensation to even higher spatial frequencies.

Plasmonic superlens image reconstruction using intensity data and equivalence to structured light illumination for compensation of losses

Imaging with a silver superlens under incoherent illumination is simulated using the finite-difference time-domain method. Conceding the use of incoherent light allows for illumination with a compact light source such as a light-emitting diode and enables both linear and nonlinear deconvolution of the resulting image with only intensity data that remains robust in the presence of Gaussian additive noise. The result is a super-resolved image of double-slit metallic mask objects with reconstructions exhibiting increased contrast and reduced full-width half-maximum. Resolution better than one-eighteenth of the free-space wavelength recovered from a previously unresolved double-slit is achieved with both deconvolution algorithms. The linear deconvolution procedure is unified with structured light illumination, directly analogous to recently proposed physical and computational loss compensation schemes, which employed coherent light. The results provide a path toward design of an ultracompact super-resolution imaging system that only requires intensity information for image reconstruction.

Analytical description of inverse filter emulating the plasmon injection loss compensation scheme and implementation for ultrahigh-resolution hyperlens

An inverse filter full analytical description and implementation of a recently proposed plasmon injection scheme for improving the resolution of a hyperlens is presented. Different types of loss mechanisms existing in the hyperlens imaging system are identified and studied in detail. It is shown that the plasmon injection scheme and its inverse filter analog can compensate all the major loss mechanisms. As a result, an object with deep subwavelength features, otherwise unresolvable with a hyperlens alone, is fully reconstructed.

Spatial filtering of evanescent waves with rough multilayer hyperbolic metamaterials

Hyperbolic metamaterials acting as spatial filters, passing incident evanescent waves and blocking incident propagating waves, can be produced for ultraviolet wavelengths by a stack of alternating metal/dielectric films. However, real fabricated devices have disordered layer surfaces due to imperfect material deposition. Here, we investigate the effect of realistic surface roughness on the spatial filtering properties of such devices. The findings have implications in subdiffraction imaging and photolithography.

Controlling optical absorption in metamaterial absorbers for plasmonic solar cells

Metals in the plasmonic metamaterial absorbers for photovoltaics constitute undesired resistive heating. However, tailoring the geometric skin depth of metals can minimize resistive losses while maximizing the optical absorbance in the active semiconductors of the photovoltaic device. Considering experimental permittivity data for InxGa1-xN, absorbance in the semiconductor layers of the photovoltaic device can reach above 90%. The results here also provides guidance to compare the performance of different semiconductor materials. This skin depth engineering approach can also be applied to other optoelectronic devices, where optimizing the device performance demands minimizing resistive losses and power consumption, such as photodetectors, laser diodes, and light emitting diodes.