This PDF file contains the front matter associated with SPIE Proceedings Volume 11368, including the title page, copyright information, table of contents, and author and conference committee lists.

Whispering gallery modes (WGMs) occur due to total internal reflection in symmetric dielectric structures. These modes have high quality (Q) factor and low mode volume (Veff). Photoluminescence (PL) of an emitter when coupled with WGMs leads to the modification in the radiative rate of the emitter. This effect on the radiative rate is known as Purcell effect. Purcell factor (FP) is proportional to Q/Veff of the cavity. Localized surface plasmon resonance (LSPR) of metal nanoparticles (NPs) can be used along with the WGMs of the microcavity to have a combined LSPR-WGM hybrid system. LSPR depends on the shape and size of the NPs which can affect FP of the microcavity. In this work, we report the effect of octopod and octahedral shaped gold nanoparticles (AuNPs) on the radiative rate of rhodamine B (RB) doped microspheres. FP values of smaller than unity have been observed indicating the inhibition of the radiative rate in the microcavity.

Regular arrays of quasi-micro-beads have been fabricated via a modified microlens array fabrication process. Thanks to surface energy modification and control, microlens have been obtained with shapes being significantly more than hemispherical, realizing regular arrays of quasi-micro-beads. This fabrication method is the only reported technique - to the best of our knowledge - enabling the massive parallelization of super-resolution imaging via nanojet thanks to the regularity of the array. Results of super-resolution imaging using these arrays will be reported and discussed.

We report the effect of coating of tungsten disulphide (WS₂) on fiberized silica microsphere resonator. Transmission measurements of the microsphere resonator have been done with the help of a tunable laser source and a tapered fiber. The quality (Q) factors have been measured for bare and WS2 coated microcavities. Results indicate that although there is a decrease of Q-factor from 10⁷ to 10⁵ after coating, it results in a cleaner spectrum. Cleaning of WGM spectra becomes important for applications such as sensing where observing a single mode resonance is essential in estimating the shift precisely. Asymmetric Fano-type profile has been observed in the clean spectrum due to the interaction of WS2 with the uncoated WGMs at 1550 nm.

In classical microscopy, the diffraction of light limits the resolving power of the system, which restricts the detailed observation of nanoscale elements. From the cut-off frequency of the optical transfer function, the lateral resolution of an optical microscope can thus be quantified as 0.5 Lambda/NA, where Lambda and NA are the wavelength of the light source and the numerical aperture of the microscope objective, respectively. A white-light microscope thus allows the visualisation of objects having a minimum size that is just greater than half of the wavelength of the illumination in air. Recently, several far-field methods have been developed in order to overcome this limitation. Microsphere-assisted microscopy is one such recent technique which allows the diffraction limit to be broken. In 2011, Wang & al. developed two-dimensional super-resolution imaging through glass microspheres. They showed that microsphere-assisted microscopy distinguishes itself from others by being able to perform label-free and full-field acquisitions. In addition, with only slight modifications of classical white-light microscopy, microsphere-assisted microscopy makes it possible to reach a lateral resolution of a few hundred nanometres (~λ/7 in immersion). Placing a microsphere on a sample, directly or at a few hundred nanometres distance allows the generation of a super-resolved virtual image of the object, which is then collected by a microscope objective. Currently several studies have been aimed at providing a better understanding of the super-resolution phenomenon in microsphere imaging. Now we know that the performance in microsphere-assisted microscopy depends on the optical and geometrical parameters. According to many studies on the PJ prediction, the imaging process in microsphere-assisted microscopy can be addressed by considering the sphere as a photonic jet lens. However, recently, we demonstrated that the photonic jet (PJ) generation by a microsphere, and considered here as the point spread function, is not small enough to justify this resolution improvement in the imaging process. Although, the size of the focus spot overcomes the diffraction limit, the full width at half maximum of the PJ waist is around a third of the wavelength, which is lower than the super-resolving power which is around λ/7 in immersion. However, the PJ phenomenon can explain the imaging through the microsphere, the nature of the image, the position of the image plane and the lateral magnification dependence provided by the microsphere. Moreover, we have investigated the contrast in the virtual image according to the relative phase difference between close point sources. When the point sources are initially in-phase, the two virtual images cannot be distinguished. However, when the point sources are initially out-of-phase, the two virtual images can be clearly distinguished. Our work considers a third hypothesis by contributing to the investigation of the role of whispering gallery modes (a radially evanescent wave) in the microsphere assisted microscopy mechanism through numerical simulations using a finite element method.

The diffraction limit of electromagnetic waves restricts the formation of sub-wavelength spots. The feasibility to generate scattered beams of light with a high-intensity main lobe, a weak sub-diffracting waist, and a very low divergence angle, named Photonic nanojets, was demonstrated traditionally with spherical particles. Various practical applications require the creation of different types of photonic jets or electromagnetic streams with specific characteristics and properties. For instance, photonic jets can be applied to ease the coupling into the optical waveguides. In this case, photonic jets play the role of a coupling element similar to the lens, grating coupler or prism. To address this challenge, we study the Fresnel Zone Plate (FZP) of rings-like shape. We show that the Babinet principle can be applied for studying the complementary diffractive structures for the formation of near-field photonic jets on a facet of the optical waveguide. Using COMSOL Multiphysics, we built a model of the Fresnel Zone Plate structure based on rings and demonstrate the applicability of Babinet’s principle for the formation of photonic jets in the near-infrared.

During last several years it was shown, that an electromagnetic field can be made to curve after propagation through a simple dielectric mesoscale Janus particle of special shape, which adds a newfound degree of simplicity. This effect was discovered by I.V.Minin and O.V.Minin and termed ‘photonic hooks’– it is an unique electromagnetic self-bending subwavelength structured light beams configuration behind a mesoscale particle with a broken symmetry and differ from Airy-family beams. PH features the radius of curvature, which is about 2 times smaller than the electromagnetic wavelength - this is the smallest curvature radius of electromagnetic waves ever reported. The nature of a photonic hook is in dispersion of the phase velocity of the waves inside of particle, resulting in interference. Here, we report an experimental verification of the photonic hook effect in terahertz waveband.

In this work we have developed new type of color splitters, which separate spectrally and spatially the light reaching image sensors by exploiting the nanojet (NJ) beam phenomenon. The goal is to channel respective R, G and B (red, green and blues) spectra to corresponding pixels, and to replace absorbant color filters for a better light efficiency management. The proposed method relies on light diffraction on the edges of constitutive parts of the studied multimaterial elements. Diffraction of light on the edge of a dielectric microstructure forms a tilted focused beam whose characteristics depend on the ratio of refractive indexes between the materials of the elements creating this edge. Combination of two or more dielectric materials with different refractive indexes leads to the creation of multiple NJs with different angles of deviation, lengths and intensities. The possibility to split color-bands of the incident light by combining two or more dielectric materials is discussed. In this way the generated NJ beams create a spectrally dependent NJ pattern in the near zone. We demonstrate that the proposed topologies of multi-material microlenses help to reduce the size of the color splitting element as well as the optical crosstalk through the dielectric layer.

In this work, we show that suitable continuous superposition of zero-order Bessel beams, combined with the use of a mathematical operator which raises the topological charge of any optical beam, allow us to structure on demand non-diffracting hollow beams endowed with orbital angular momentum (OAM) within micrometer spatial domains. Our Analysis is exact and analytical, fully based on the Maxwell equations. Such method can find potential applications in many fields, especially those which require the use of highly non-paraxial optical beams, like optical tweezers, optical guiding of atoms, control of the OAM over microscopic regions and photonics in general.

This March 2020, Professors Igor V. Minin and Oleg V. Minin, Doctors of Physics, correspondent members of Russian Academy of Metrology, outstanding scientists in the field of diffractive optics, terahertz photonics and calculation experiment technology, has marked their 60-th anniversary. This article gives a brief review of their life-time achievements in science and education. We briefly analyze the jubilee’s contribution to the development of photonics, diffractive optics, shock waves, cumulative jets, field localization by mesoscale particles, and acoustic.

We report the study of light absorption efficiency of a hollow spherical microparticle (microcapsule) doped with strongly absorbing gold nanoparticles of spherical and cylindrical spatial shapes. By means of the FDTD numerical simulations, the absorption spectra of a doped microcapsule in the visible and near-IR spectral regions (from 0.5 μm to 0.9 μm) are calculated. Based on the research results we can draw the several conclusions. First, the absorption efficiency of initially transparent spherical microcapsule is effectively tailored by doping the necessary amount of strongly absorbing nanometersized metal (gold) particles. Meanwhile, with a rather low volume fraction of nano-inclusions in the capsule shell (~ 18%) it is possible to rise its absorption cross-section to the value of an absolutely absorbing sphere. Next, the spectral absorption of a microcapsule turns out to be quite non-uniform in the considered wavelength range of incident radiation and depends on the morphology of nano-inclusions. In some spectral regions, substantial capsule absorption enhancement is realized due to the resonant excitation of surface plasmons in nanoparticles (from 540 nm to 570 nm for spheres, from 670 nm to 770 nm for rods of various form factors). In the long-wavelength wing of the spectrum, the efficiency of absorption of a nanoparticle-doped capsule as a rule decreases due to its Mie-parameter decrease and a drop in the absorption coefficient of bulk gold. The chromatic dispersion of microcapsule absorption decreases with the increasing of volume content of plasmonic nanoparticles. By simultaneous combining gold nanoparticles of various shapes (spheres and rods), it is possible to obtain a quasi-neutral absorption of composite capsule in the considered wavelength range. Finally, the absorptivity of a nanoparticle-doped microcapsule can be calculated using the effective homogenized medium formulae mainly in the conditions of weak chromatic dispersion of capsule absorption. This situation is usually realized with cylinder-shaped nano-inclusions or at high levels of total shell absorption. Besides, the Bruggeman mixing rule does not capture the surface plasmon resonances of nanoparticle-dope.

In this communication, we describe the operating principle of a polarization-sensitive dichroic filter consisting of a multilayered photonic structure with an embedded anisotropic composite layer. Our goal is to obtain two separate narrow passbands for two mutually orthogonal polarizations of light. To that effect, we propose to combine a photonic crystal structure with a two-dimensional array of spheroidal metallic nanoparticles. The former consists of two distributed Bragg reflectors surrounding a cavity layer that ensures the existence of narrow transmission peaks (defect modes) in the photonic bandgaps of the structure. The polarization sensitivity of transmittivity and reflectivity is provided by the rectangular array of spheroidal metallic nanoparticles embedded at the center of the cavity layer, in which the excitation of surface plasmon resonances depends on the relative orientations of the anisotropy axes of the nanoparticles and the polarization direction of the incoming light wave.