Search results for: Vasily N. Astratov
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Laser & Photonics Reviews > 17 > 12 > n/a - n/a
Label‐free super‐resolution (LFSR) imaging relies on light‐scattering processes in nanoscale objects without a need for fluorescent (FL) staining required in super‐resolved FL microscopy. The objectives of this Roadmap are to present a comprehensive vision of the developments, the state‐of‐the‐art in this field, and to discuss the resolution boundaries and hurdles that need to be overcome to break...
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Laser & Photonics Reviews > 17 > 12 > n/a - n/a
Roadmap on Label‐Free Super‐Resolution Imaging
In article number 2200029, Vasily Astratov and colleagues representing 27 research teams worldwide created a roadmap on label‐free super‐resolution imaging. Its scope spans from diffraction‐limited interference detection techniques to methods allowing to overcome classical diffraction limit without using fluorescent markers, which are based on information...
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Laser & Photonics Reviews > 17 > 9 > n/a - n/a
One of the most significant developments in life sciences—the discovery of bacteria and protists—was accomplished by Antoni van Leeuwenhoek in the 17th century using a single ball lens microscope. It is shown that the full potential of single lens designs can be realized in a contact mode of imaging by ball lenses with a refractive index of n ≈ 2, suitable for developing compact cellphone‐based microscopes...
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Based on analogy between quantum mechanics and the classical electrodynamics, we sorted dielectric microspheres with almost identical positions of their whispering gallery mode (WGM) resonances as photonic atoms. Such microspheres were assembled in a wide range of structures including linear chains and planar photonic molecules. We studied WGM hybridization effects in such structures using side coupling...
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The mechanisms of super-resolution imaging by contact microspherical (or microcylindrical) nanoscopy remain an enigmatic question since these lenses neither have an ability to amplify the near fields like in the case of far-field superlenses, nor they have a hyperbolic dispersion similar to hyperlenses. In this work we study theoretically and numerically the resolution of point sources which are imaged...
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A classification of label-free super-resolution imaging mechanisms is given based on the nonlinear reduction of the point-spread function (PSF), near-field scanning, image magnification and gain, structured and sparse illumination, and information approaches. We argue that the super-resolution capability of contact microspheres stems from an image magnification effect taking place in close proximity...
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Laser & Photonics Reviews > 11 > 2 > n/a - n/a
This work takes inspiration from chemistry where the spectral characteristics of the molecules are determined by hybridization of electronic states evolving from the individual atomic orbitals. Based on analogy between quantum mechanics and the classical electrodynamics, we sorted dielectric microspheres with almost identical positions of their whispering gallery mode (WGM) resonances. Using these...
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Annalen der Physik > 528 > 11-12 > 901 - 904
In a comment [A. Darafsheh, Ann. Phys. (Berlin) 528 (2016)] on our paper [K. W. Allen et al., Ann. Phys. (Berlin) 527, 513–522 (2015)], the results and conclusions of our work were doubted along two directions. The first is related to the methodology of our resolution quantification and use of confocal microscopy. The second is related to the mathematical treatment of our magnification measurements...
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The use of contact microlenses first started being used as a simple method which allows resolving nanometer sized objects using visible light. The resolution beyond the classical diffraction limit has been reported for nanoplasmonic structures. However the mechanism is not fully understood whether it is from photonic nanojets, plasmon-polaritons, localized surface plasmon resonances, coherent modal...
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In this work, we propose and optimize several designs of mid-IR focal plane arrays (FPAs) where individual pixels are integrated with dielectric microspheres to provide maximal light collection efficiency in combination with large angle-of-view (AOV). The designs are developed for back-illuminated FPAs with progressively shorter effective focal length to increase AOV by more than an order of magnitude...
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Through numerical modeling, we study routing of the light pulses in coupled cylindrical whispering gallery mode microresonators. The coupling of light in and out of such structures is provided using strip-waveguides. We show that such photonic molecules display a complicated resonant behavior, leading to a nonreciprocal transport and a wavelength-dependent connectivity of the optical ports.
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The use of contact microlenses attracted a great deal of attention recently because in the case of imaging nanoplasmonic structures it showed the resolution values exceeding the classical diffraction limit. The mechanisms that allow for this type of imaging are presently still debated in the literature; these range from photonic nanojets, plasmon-polaritons, localized surface plasmon resonances and...
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Optical nanoscopy with contact microlenses emerged as a simple method which allows overcoming the classical diffraction limit represented by the Abbe's formula. The mechanisms of such imaging are debated in the literature including photonic nanojets, plasmon-polaritons, localized surface plasmon resonances and coherent modal excitations in metallic objects, as well as optical resonances in microspherical...
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Despite all the success with developing super-resolution imaging techniques, the Abbe limit poses a severe fundamental restriction on the resolution of far-field imaging systems based on diffraction of light. Imaging with contact microlenses, such as microspheres or microfibers, can increase the resolution by a factor of two beyond the Abbe limit. The theoretical mechanisms of these methods are debated...
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Dielectric microspheres, with sizes on the order of several wavelengths, support high-quality whispering gallery (WG) modes and provide nonresonant focusing of light into tiny spots termed nanoscale photonic jets. In this chapter, we review properties of more complicated multiple-cavity systems that are formed by microspheres assembled in chip-scale structures. The resonant optical properties of such...
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Annalen der Physik > 527 > 7-8 > 513 - 522
Microsphere‐assisted imaging has emerged as an extraordinary simple technique of obtaining optical super‐resolution. This work addresses two central problems in developing this technology: i) methodology of the resolution measurements and ii) limited field‐of‐view provided by each sphere. It is suggested that a standard method of resolution analysis in far‐field microscopy based on convolution with...
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Microsphere-assisted ultramicroscopy is a powerful, yet simple, technique to visualize nanometric-scale objects with visible light. In this method, dielectric microspheres are placed in contact with the nanoscale objects, so that the spheres experience object's optical near-fields. The mechanism of imaging is still debated in the literature; however it is likely to involve surface plasmon resonances...
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In 2011, super-resolution imaging by microspheres emerged as an extraordinary simple and broadband technique. The mechanism of imaging remains a mystery still today. The most likely candidates are the optical near fields, plasmonic resonances, photonic nanojets and whispering gallery modes. The critical problem in this area is the experimental definition of resolution which historically has been based...
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Resonances can give rise to the appearance of large and highly frequency selective optical forces on microparticles. The forces are studied in two cases: when intrinsic resonances in dielectric particles exist and when resonances are created as a result of the interaction of particles with waveguides. The resonant forces can be used for high accuracy particle sorting and power-efficient particle manipulation.
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Photonic molecules formed by microresonators with coupled whispering gallery modes were studied by finite-difference time-domain modeling. Mode splitting was observed due to coherent coupling. Spatial mode distribution was shown to be different for each coupled mode. The advantages of photonic molecules over single resonators for sensing applications were demonstrated.
