In lensless microscopy, spatial resolution is usually provided by the pixel density of current digital cameras, which are reaching a hard-to-surpass pixel size / resolution limit over 1 µm. As an alternative, the dependence of the resolving power can be moved from the detector to the light sources, offering a new kind of lensless microscopy setups. The use of continuously scaled-down Light-Emitting Diode (LED) arrays to scan the sample allows resolutions on order of the LED size, giving rise to compact and low-cost microscopes without mechanical scanners or optical accessories. In this paper, we present the operation principle of this new approach to lensless microscopy, with simulations that demonstrate the possibility to use it for super-resolution, as well as a first prototype. This proof-of-concept setup integrates an 8 × 8 array of LEDs, each 5 × 5 μm2 pixel size and 10 μm pitch, and an optical detector. We characterize the system using Electron-Beam Lithography (EBL) pattern. Our prototype validates the imaging principle and opens the way to improve resolution by further miniaturizing the light sources.
The physical laws of diffraction limit the spatial resolution of optical systems. In contrary to most superresolution microscopy approaches used today, in our novel idea we are aiming to overcome this limit by developing a spatially resolved illumination source based on semiconductor nanoscale Light Emitting Diode (nanoLED) arrays with individual pixel control. We present and discuss the results of optical simulations performed for such nanoLED emitter arrays and analyze the theoretical limits of this approach. As possible designs we study arrays of GaN nanofins and nanorods (obtained by etching nanofin arrays), with InGaN/GaN multi quantum wells embedded as active regions. We find that a suitable choice of the array dimensions leads to a reasonably directed light output and concentration of the optical power in the near field around an activated pixel. As a consequence, the spatial resolution for this type of microscopy should only be limited by the pixel pitch, and no longer by the optical diffraction. Realization of optimized nanoLED arrays has a potential to open new field of chip based superresolution microscopy, making super-high spatial resolution ubiquitously available.
In strongly coupled light matter systems electronic energy levels become inextricably linked to local electromagnetic field modes. Hybridization of these states opens new relaxation pathways in the system, particularly important for plasmon decay into single electron states, known as hot carriers. We investigate the influence of the coupling strength between a plasmonic resonator and a molecule on hot carrier generation using first principles calculations. An atomistic approach allows the capture of changes in the electronic structure of the system. We show that hot carriers are not only preferably generated at excitation frequencies matching the new polaritonic resonances, but their energy distribution strongly deviates from the one corresponding to the non-interacting system. This indicates existence of new plasmon decay paths due to appearance of hybridized nanoparticle–molecule states. We observe also direct electron transfer between the plasmonic nanoparticle and the molecule. Therefore, we may conclude, that bringing plasmonic nanostructures in strong interaction with molecules gives the ability to manipulate the energy distribution of the generated hot carriers and opens possibility for charge transfer in the system.
We analyze the microscopic mechanism of the improvement of solar cell efficiency by plasmons in metallic components embedded in active optical medium of a cell. We focus on the explanation of the observed new channel of plasmon photovoltaic effect related to the influence of plasmons onto the internal cell electricity beyond the previously known plasmon mediated absorption of photons. The model situation we analyze is the hybrid chemical perovskite solar cell CH3NH3PbI3−αClα with inclusion of core–shell Au/Si02 nanoparticles filling pores in the Al2O3 or TiO2 porous bases at the bottom of perovskite layer, application of which improved the cell efficiency from 10.7 to 11.4% and from 8.4 to 9.5%, respectively, as demonstrated experimentally, mostly due to the reduction by plasmons of the exciton binding energy.
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