The photonic hook (PH) generated by a partially illuminated high-index dielectric particle hemi-immersed in the dielectric film is investigated. A tunable PH is generated from a cylinder deposited on a dielectric film, and the cylinder is partially illuminated by the placement of a thin, flat aluminum mask in front of it. The effects of film type, mask width, and height of dielectric film are mainly discussed. The results provide a novel design method for PHs, which have potential applications in optical manipulation and high-resolution imaging.
Water droplets are a highly abundant phase-change material to realize tunable optical lenses. We demonstrated for the first time that freezing mesoscale water droplets could be used as a tunable optical lens, such that freezing becomes an asset despite the low absolute values of the refractive indices of the shell and core materials and their optical contrast. It is shown that the dielectric shell of mesoscale water droplets in solid ice allows controlling both the maximum field intensity and the focus position of the formed photonic nanojet. The ice formation with air bubbles during the freezing of a water droplet is appropriate for a dynamic increase in the range of change of the focal position compared to solid ice. The proposed concept of a tunable spherical lens based on a freezing water drop can be used for microscopy and optical trapping in "green" mesotronics.
Dielectric mesoscale spheres have aroused strong interest because of their potential to localize light at deep subwavelength volume and to yield extremal internal magnetic and/or electric field enhancements. Recently, it was showed that such particle could support high-order Mie resonance modes with giant field localization and enhancement. Optimizing the internal fields appears as a key challenge for enhancing wave matter interactions in dielectric mesoscale particles. However, a dielectric particle is always located in some medium, and not in a vacuum. Moreover, the question is how much the environment medium affects the internal field intensities enhancement in the super-resonance effect. Based on Mie theory we show for the first time that the presence of the environment leads to a significant decrease in the intensity of the field in the particle. Thus, the study of the effect of super-resonance becomes meaningless without taking into account the environment. However, a greater enhancement of the internal field is found for the blue-shifted Mie size parameter of the sphere when the particle, for example, is in air rather than in vacuum.
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.
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