Optical magnetic lens: towards actively tunable terahertz optics.

As we read this text, our eyes dynamically adjust the focal length to keep the image in focus on the retina. Similarly, in many optics applications the focal length must be dynamically tunable. In the quest for compactness and tunability, flat lenses based on metasurfaces were introduced.

Homogeneous enhancement of near-fields in all-dielectric metasurfaces with cluster-based unit cells.

To construct a dielectric analog of a spaser, we study several configurations of cluster-based unit cells for an all-dielectric metasurface characterized by resonant conditions of the trapped mode excitation. Excitation of the trapped mode is realized by performing either specific displacement of particles in the cluster or perturbation of the equidistantly spaced particles by off-centered holes. The latter approach is more advantageous for enhancement of the electric near-field with homogeneous distribution in-plane of the structure and strong field localization outside the high-refractive-index dielectric particles.

High-quality trapped modes in all-dielectric metamaterials.

A planar all-dielectric metamaterial made of a double-periodic lattice whose unit cell consists of a single subwavelength dielectric particle having the form of a disk possessing a penetrating hole is considered. The resonant states in the transmitted spectra of the metamaterial are identified considering modes inherent to the individual cylindrical dielectric resonator. A correlation between the asymmetry in the particle's geometry, which arises from the off-centered displacement of the hole and the formation of the Mie-type and trapped modes, is established.

Nanostructured metal film with asymmetric optical transmission.

We demonstrate for the first time a nanostructured planar photonic metamaterial transmitting light differently in forward and backward directions.