Optical wireless communication (OWC) is envisioned to become an indispensable technology in future wireless networks. However, one of the main issues hindering the widespread of OWC systems is the strict alignment required to maintain connectivity. This is due to the tradeoff between the receiver’s active area and its response speed, which necessitates the use of a lens to focus the light, limiting the field of view (FOV). Taking inspiration from the wide-FOV eyes of horseflies to address this issue, we propose the use of a convex-surface fused fiber-optic taper (FFOT) that can effectively expand a planar array of photodetectors and project it onto a spherical dome, respectively improving the light collection of individual photodetectors and expanding the overall FOV of the array. In our proof-of-concept demonstration, we show an optical receiver with a FOV semi-angle of around 25° and optical power density gain up to 120 in a 1-GHz link whose bandwidth is limited only by the photodetector. Moreover, reducing of the FOV of each individual fiber that results from tapering and the extra-mural absorption material incorporated around the fibers’ cores reduce the crosstalk between them, preserving the image quality. Therefore, unlike non-imaging light focusing elements, FFOTs can potentially be used in applications in which preserving the image is necessary, such as in imaging multiple-input and multiple-output systems and light detection and ranging (LiDAR). We also show the performance of FFOTs in collecting light from color-converting materials, a technique used in expanding the FOV beyond the étendue limit.

PNJs are non-resonant travelling beams with applications in enhanced Raman scattering, coupled resonator optical waveguide, high resolution microscopy, lithography and nonlinear optics. The length and beam width of the PNJ can be controlled by engineering the shape of the dielectric structure as well as by changing the refractive index contrast between the particle and the surrounding medium. The waist of PNJ moves towards the diffracting particle with increase in refractive index, and for refractive indices higher than 2, the waist is inside the particle. This migration of beam waist towards the interior of the particle is the biggest hurdle in on chip PNJ generation, because many CMOS compatible materials, including Silicon has refractive index higher than 2. In this study, we present the design and computational results of a photonic chip made of Silicon that can support PNJ outside the material boundary. We have studied the characteristics of PNJ including the width and length as well as the effect of surrounding medium.

Various attempts have been discussed to overcome the lateral resolution limit and thus to enlarge the fields of application of optical interference microscopy. Microsphere assisted microscopy and interferometry have proven that the imaging of structures well below Abbe’s resolution limit through near-field assistance is possible if microspheres are placed on the measured surface and utilized as near-field assisting imaging elements. The enhancement of the numerical aperture by the microspheres as well as photonic nanojets were identified to explain the resolution enhancement, but also whispering gallery modes and evanescent waves are assumed to have an influence. Up to now, to the best of our knowledge there is no complete understanding of the underlying mechanisms and no model enabling to examine ideal imaging parameters. This contribution is intended to clarify, how much the lateral resolution of an already highly resolving Linnik interferometer equipped with 100x, NA 0.9 objective lenses can be further improved by microspheres. Our simulation model is based on rigorous near-field calculations combined with the diffraction limited illumination and imaging process in an interference microscope. Here, we extend the model with respect to microsphere assisted interference microscopy providing a rigorous simulation of the scattered electric field directly above the sphere. Simulation and experimental results will be compared in the 3D spatial frequency domain and discussed in context with ray-tracing computations in order to achieve an in-depth understanding of the underlying mechanism of resolution enhancement by the mircosphere.

Extreme field localization and giant field enhancement are often achieved by using plasmonic nanostructures and metamaterials such as strongly coupled silver nanoparticles. Dielectric particles and structures can focus light beyond the diffraction limit (photonic nanojet effect), but with much weaker strengths. Recently, we showed that dielectric microspheres could support high-order Mie resonance modes ('super-resonance modes'), that can generate similar level of electric field intensity enhancement as plasmonic structures on the order of 10⁴-10⁷. In this work, we aim to further advance our understanding of the super-resonance modes. New results on the effects of size parameter and refractive index on optical super-resonances across a wide parameter range and with improved numerical accuracies is presented. The results suggest that the electric field intensity enhancement could reach a record high level of 10⁹-10¹¹ at specific conditions that surpass plasmonic enhancements. Moreover, super-resonance-enabled focusing by microsphere lens under different lighting sources (e.g., different color LEDs or lasers, halogen lamps) is investigated and compared for the first time. These results are important in understanding the super-resolution mechanism for microsphere nanoscopy and will find numerous potential applications in photonics.

It is shown that the resolution of portable and lightweight smartphone-based microscopy can be increased up to the diffraction limit by using imaging through ball lenses with refractive index sufficiently close to n=2 under contact conditions with nanoplasmonic and biomedical samples. It is demonstrated that the millimeter-scale ball lenses made from LASFN35 glass with n=2.02 at λ = 600 nm allow achieving extraordinarily high image magnification up to 50u. Under these conditions, it is possible to move away from the conventional resolution limitations of cellphone microscopy determined by the pixilation of the images and to reach the diffraction-limited resolution ~600 nm. It is shown that the dispersion of n allows tuning of magnification in a very broad range. The magnification values are explained by the exact numerical solution of the Maxwell equations and a good agreement with the experiment is demonstrated. We performed smartphone imaging of different biomedical samples such as melanoma and human aorta and demonstrated that the quality of imaging is comparable to that in conventional microscopy with the 10× objectives. The in-principle possibility is suggested of melanoma diagnostics based on observation of distribution of lymphocyte cells by application of cellphone microscope to the patient’s skin without a need to make histological samples.

As the tweezer light sources, single beam optical traps, have become a kind of important tool for non-contact manipulation of microscopic objects. The interaction of light-sheets with objects allows flow visualization, nondestructive optical sectioning and imaging of the internal subcellular features. In the framework of GLMT, based on the vector angular spectrum decomposition method, with the Lorenz gauge condition and Maxwell’s equations allow adequate determination of the Cartesian components of the incident radiated electric field components. The Bessel pincer light-sheets with characteristics of auto-focusing and self-bending, has great advantages in non-destructive optical sectioning and imaging of the internal subcellular features. The influences of the Bessel pincer light-sheets (mainly focusing on beam order and scaling parameter) acting on a dielectric sphere particle, will be discussed. The results will show the sensitivity of beam parameters (beam order and scaling parameter) to the radiation force and the negative force. Further, the present solution can be used to calculate the optical torque, which is of great importance in particle transport and rotation.

The optical spin torque (OST) on a magneto-dielectric Mie sphere has been discussed and analyzed analytically in this investigation, using the Generalized Lorenz-Mie theory (GLMT). The incident electromagnetic field is an Airy light-sheet, with the parameters transverse scale kω₀ and attenuation parameter γ, where kω₀ modulates the width of the main lobe of the Airy light-sheet, and γ controls the attenuation of Airy light-sheet. The effect of kω₀ and γ of Airy light-sheet on the OST has been studied. The size parameters ka, permittivity, and permeability of the magneto-dielectric Mie sphere have also been discussed. This investigation of the optical spin torque (OST) on the magneto-dielectric Mie sphere has specific reference significance and is expected to be applicable to the field of manipulation of microparticles and biomedicine.

The optical spin torque (OST) exerted on a dielectric Rayleigh spherical particle by photonic hook is investigated in the framework of dipole approximation. Optical spin torque is a type of optical torque that causes a particle to rotate around its center of mass. I.V. Minin and O.V.Minin discovered the photonic hook phenomenon in 2015 (Patent of Russia 161207). They used the combined structure of cube and prism to form a curved beam to pull a small particle, which caused a great sensation in the field of photonics. In this paper, the photonic hook is generated by a plane wave illuminating a dielectric irregular cuboid with one corner cut off. The effects of wavelength and slope of cutting of the irregular cuboid on the OST are analyzed. The numerical results show that the wavelength and inclination of cutting greatly affect the OST. Optical spin torques contain a large amount of negative torques and are sensitive to the slope of cutting of the irregular cuboid. The results of this paper are expected to provide theoretical support for the manipulation and rotation of Rayleigh particles in structured wavelength-scaled localized beams.

Here we create a holographic trap that allows trapping with scalar Gaussian and vortex beams, as well as vectorial combinations of the two. When equally weighted, the resultant is a propagation invariant flat-top beam trap. The set-up includes a spatial light modulator in an interferometer to combine the beams, an inverted microscope for imaging, and a photon counting fluorescence detection stage. We outline the functionality of this system, measure the trap stiffness for some example beams, and show in-situ fluorescence measurement from quantum dots attached to micro-scale beads.

Some new unusual physical phenomena and effects associated with dielectric mesoscale particles with Mie size parameter near 10 were studied and have been discovered during the last decade. In this paper, we propose nanoholes structured wavelength-scaled dielectric cubic particle with refractive index near two, where the array of nanoholes can act as a plurality of near-field probes to simultaneously illuminate the sample surface and it has the potential of surpassing the performance of most existing nearfield imaging approaches. We also offer the concept of the single nano-structuring of a dielectric cylinder or sphere made from conventional optical materials. The choice of the diameter of the nanohole in the particle "transfers" it into the resonance mode, when the characteristics of the field localized in the shadow part of the particle are determined not by the wavelength, but by the size of the nanohole. Thus, the diameter of the focused spot at the exit from the particle can be much smaller than the solid immersion diffraction limit.

Viruses are unseen enemies which tend to disarmingly spread from person-to-person, therefore causing health damages and weakens the immunity system. Their invisibility give rise to various representations, projections and imaginations that allow laypeople to tame the unseen and intangible nature of viruses. For the first time to our knowledge, we are proposing a novel and uncommon scientific approach resting on the synergy between two scientific field: Technical Sciences & Medicine (TSM) with Social Sciences and Humanities (SSH). Therefore, we present the results of our investigations concerning the evaluation of the social impact of the scientific image of free virions on a specific population, particularly affected by the Covid-19 pandemic: people over 60 years old. For this research, we have implemented two scientific imaging solutions to visualize the free viral particles of SARS-CoV-2. The first one is a standard solution of electron microscopy and the second one is an optical and computational solution of microscopy. The scientific representations of SARS-CoV-2 that we have proposed is in fact highly different from the mass media image that we can see everywhere. Concerning the targeted population, we have demonstrated that the scientific image has a negative impact on the population. Thus, the socially constructed representations of these invisible enemies have a preponderant role in driving laypeople’s emotional reactions and health-related behaviors. Therefore, imaging viruses remains a critical scientific effort that contributes irrevocably to alleviate laypeople’s misrepresentations of these invisible enemies.

Some new unusual physical phenomena and effects associated with dielectric mesoscale particles with typical Mie size parameter around 10 were studied and have been discovered during the last decade. There are: optical nanovortices; anapoles; photonic nanojets and terajets as in transmission as in reflection modes; structured fields in the form of photonic hooks and loops with subwavelength curvature; effects of anomalous apodization; high-order Fano resonances; effects associated with the generation of extreme magnetic and acoustic fields; effects of overcoming the diffraction limit; anomalous Gouy phase shift; flat focusing mirrors, and others. This brief review presents the authors’ approach to these problems. The focus of this review is on structural design, numerical simulation, demonstration of new concepts and functionalities, application of the proposed principles in devices. The presence of a number of interesting applications in optics, terahertz, acoustics and plasmonics indicates that in optics, terahertz, acoustics and plasmonics a new promising direction arose, which can be called as “mesotronics”.

We use spin-orbit interaction (SOI) effects of light in tight focusing by optical tweezers to engineer the dynamics of birefringent microparticles at different spatial locations close to the focal region of the tweezers. Thus, we tightly focus radially and azimuthally polarized first order vortex (Laguerre-Gaussian) beams - that do not carry intrinsic orbital angular momentum (OAM) - into a refractive index stratified medium, and observe multiple birefringent particles orbiting around a single particle trapped stably at the beam center. This is due to the fact that tight focusing induces a longitudinal component of the electric field in the case of radial polarization, which completely modifies the intensity distribution, creating finite intensity at the center - which is typically dark for vortex beams. The intensity at the beam center and off-axis - in an annular ring - are both enhanced on introducing a refractive index stratified medium in the path of the optical tweezers, so that particles are trapped in both regions. In addition, the presence of the longitudinal component leads to an additional transverse spin angular momentum (TSAM) and extrinsic transverse orbital angular momentum (ETOAM). The latter causes single or multiple birefringent particles trapped in the annular ring to rotate around the beam axis, while a single particle is also trapped without displaying rotation or translation. This demonstrates the effectiveness of SOI in engineering the dynamics of mesoscopic particles in optical tweezers.