Roadmap on Label-Free Super-Resolution Imaging.

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 which need to be overcome to break the classical diffraction limit of the LFSR imaging. The scope of this Roadmap spans from the advanced interference detection techniques, where the diffraction-limited lateral resolution is combined with unsurpassed axial and temporal resolution, to techniques with true lateral super-resolution capability which are based on understanding resolution as an information science problem, on using novel structured illumination, near-field scanning, and nonlinear optics approaches, and on designing superlenses based on nanoplasmonics, metamaterials, transformation optics, and microsphere-assisted approaches.

Half-space invisible states in dielectric particles.

The concept of invisible optical states in dielectric particles is developed. Two cases for excitation of invisible states are discussed. The first one is the excitation in the microparticles with fixed shapes (e.

Trapped modes in particles with a negative refractive index.

The natural oscillations of the electromagnetic field in a particle made from left-handed metamaterial, where both permittivity and permeability are negative, are considered. Based on the exact solution of the sourceless Maxwell equations, it is shown that due to the opposite directions of the phase and group velocities in the metamaterial, natural oscillations in such particles decay exponentially at infinity, that is, these natural oscillations can be considered as trapped modes with a finite energy. The manifestation of such modes in experiments with Bessel beams is also discussed.

Transverse Kerker effect in all-dielectric spheroidal particles.

Kerker effect is one of the unique phenomena in modern electrodynamics. Due to overlapping of electric and magnetic dipole moments, all-dielectric particles can be invisible in forward or backward directions. In our paper we propose new conditions between resonantly excited electric dipole and magnetic quadrupole in ceramic high index spheroidal particles for demonstrating transverse Kerker effect.