The promise of high-resolution imaging beyond the diffraction limit has been a core motivation for research in the fields of metamaterials and plasmonics. However, the problems with material losses have quelled some of the enthusiasm which once existed. Here, we review our recent approach relying on imaging theory and correlations to push the limits of super-resolution imaging in the presence of losses and noise. Starting with plasmon injection scheme for compensating losses, we subsequently extended the same principle to a broad range of near-field and far-field imaging systems involving both coherent and incoherent light, and hence termed this approach more encompassing active convolved illumination" (ACI). In ACI a relatively narrow range of spatial frequencies are amplified at a time. Since the total power in the active image does not change significantly, the spectral SNR is significantly improved in the region of amplification. This improves the overall resolution of the images. We also present potential extension of ACI into different research domains including atmospheric imaging, time-domain spectroscopy, and quantum computing.
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.
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.
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