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Large field-of-view super-resolution image obtained by manipulating submerged microsphere
摘要： Images with super-resolution can be obtained by dielectric microspheres with appropriate refractive index. However, in practical applications, the microsphere must be moved to the desired position and can scan the large specific area. Here we present a simple method of positioning a microsphere by using a four-dimensional precision translation stage. The simulations have been performed to confirm that 16 μmφ barium titanate glass (BTG) microsphere submerged in alcohol can obtain high quality images and the influence of the probe and the flowing liquid on imaging can be ignored. Therefore, by driving the translation stage, the submerged microsphere can scan the sample surface along the X and Y axis at the speed of 10 μm/s and the large field-of-view image can be achieved by stitching the pictures of different positions. This work has provided a new technique in super-resolution imaging and can be widely applied in field of scientific research.
关键词： photonic nanojet,scanning,super-resolution imaging,large field-of-view,microsphere
更新于2025-09-23 15:21:21
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Internal electromagnetic waves, energy trapping, and energy release in simple time-domain simulations of single particle scattering.
摘要： During the decay phase of the interaction of a femto-second Gaussian pulse with a single spherical particle, the presence of quasi-periodic short oscillatory bursts of electromagnetic energy at points in the near field outside the particle have been observed in three-dimensional simulations. Analogous behavior can be very easy produced and understood in simple one-dimensional scattering calculations. In two dimensions the situation immediately becomes more complicated and interesting. Here we discuss results from two-dimensional pseudo-spectral time-domain simulations of scattering from circular, elliptical, and hexagonal particles with the real index of refraction m=1.3. Our focus is on how energy initially trapped within a particle after interaction with an incident Gaussian pulse is released over time, and we show two kinds of events that can result in 'bursts' of energy release from the particles: (i) the coalescence of counter-propagating wave-packet-like electromagnetic field structures that have maximum amplitude near the surface of the particle, and (ii) encounters of individual packets with surface regions of high curvature. The coalescence events in the circular case show the dynamical origin of a two-dimensional form of 'photonic nanojet.' The two-dimensional simulations make clear the reason for quasi-periodic intermittent bursts at fixed near-field points outside the particle. Examination of field evolution shows that distinct near-surface internal field maxima, ostensibly the 'source' of the emission bursts, are in fact inter-connected by caustic-like internal field structures that extend throughout the particle and have complex time evolution. The revealed intricacy of these connections suggests that understanding the origins of pulsed emissions in three dimensions, even for simple particle geometries, may be quite challenging.
关键词： caustic evolution,photonic nanojet,single particle scattering,femtosecond Gaussian pulses,internal electromagnetic waves
更新于2025-09-19 17:15:36
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Quantum Dots Luminescence Collection Enhancement and Nanoscopy by Dielectric Microspheres
摘要： In recent years, dielectric microspheres have been used in conjunction with optical microscopes to beat the diffraction limit and to obtain superresolution imaging. The use of microspheres on quantum dots (QDs) is investigated, for the first time, to enhance the light coupling efficiency. The enhancement of the QD luminescence collection in terms of extraction and directionality is demonstrated, as well as the enhancement of spatial resolution. In particular, it is found that a dielectric microsphere, placed on top of an epitaxial QD, increases the collected radiant energy by about a factor of 42, when a low numerical aperture objective is used. Moreover, if two or more QDs are present below the microsphere, the modification of the far field emission pattern allows selective collection of the luminescence from a single QD by simply changing the collection angle. Dielectric microspheres present a simple and efficient tool to improve the QD spectroscopy, and potentially QD-based devices.
关键词： microspheres,photoluminescence,photonic nanojet,near field
更新于2025-09-16 10:30:52
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Localized Photonic Jets Generated by Step-Like Dielectric Microstructures
摘要： In this contribution we reveal how the step-like topology of a microstructure can contribute to the formation of a single high-intensity nanojet (NJ) beam located on its axis of symmetry. The proposed method for generating condensed optical NJ beams relies on the complex electromagnetic phenomenon associated with the light diffraction on the edges of step-like dielectric microstructures embedded in a host medium with lower refractive index. The possibility of NJ beam intensification in the near zone of such microstructure illuminated by a plane wave is demonstrated and explained by the recombination of multiple NJ beams associated with different edges or edge segments of the step-like microlens. We demonstrate that by changing materials of the layers we can intensify the NJ beam. We examine the dependence of the generated beam on the step size, shape and material.
关键词： near field focusing,microlens,photonic nanojet,edge diffraction
更新于2025-09-09 09:28:46