Optical metasurfaces are thin-layer subwavelengthpatterned structures that interact strongly with light. Metasurfaces have become the subject of several rapidly growing areas of research, being a logical extension of the field of metamaterials towards their practical applications. Metasurfaces demonstrate many useful properties of metadevices with engineered resonant electric and magnetic optical responses combined with low losses of thin-layer structures.Here we introduce the basic concepts of this rapidly growing research field that stem from earlier studies of frequencyselective surfaces in radiophysics, being enriched by the recent development of metamaterials and subwavelength nanophotonics. We review the most interesting properties of photonic metasurfaces, demonstrating their useful functionalities such as frequency selectivity, wavefront shaping, polarization control, etc. We discuss the ways to achieve tunability of metasurfaces and also demonstrate that nonlinear effects can be enhanced with the help of metasurface engineering.

When the constitutive materials of photonic crystals (PCs) are magnetic, or even only a defect introduced in PCs is magnetic, the resultant PCs exhibit very unique optical and magneto-optical properties. The strong photon confinement in the vicinity of magnetic defects results in large enhancement in linear and nonlinear magneto-optical responses of the media. Novel functions, such as band Faraday effect, magnetic super-prism effect and non-reciprocal or magnetically controllable photonic band structure, are predicted to occur theoretically. All the unique features of the media arise from the existence of magnetization in media, and hence they are called magnetophotonic crystals providing the spin-dependent nature in PCs.

Optical second harmonic generation (SHG) is studied from multilayer graphene films in the presence of DC electric current flowing in the sample plane. Graphene layers are manufactured by chemical vapour deposition (CVD) technique and deposited on an oxidised Si(001) substrate. SHG intensity from graphene layer is found to be negligible in the absence of the DC current, while it increases dramatically with the application of the electric current. The current-induced change of the SHG intensity rises linearly with the current amplitude and changes its sign under the reversal of the current direction to the opposite. The observed effect is explained in terms of the interference of second harmonic radiation reflected from the Si surface and that induced by the DC current in multilayer graphene.Since its first experimental realisation in 2004 graphene continues to attract enhanced interest as a prospective material for both fundamental and applied science. Fascinating electronic properties which include electric fieldeffect[1], "chiral" quantum Hall effects [2,3], prospects for spintronics [4] and valeytronics [5] immediately pushed graphene research to the cutting edge of modern nanomaterial science and technology. Among the numerous problems currently being studied for graphene is the possible connection between the electron transport and the nonlinear-optical response. The importance of this task is dictated not only by needs of the applied research as allows distant probing of the electron flow in graphene devices but, perhaps, more importantly as a route to gain new comprehensive insight into its fundamental electronic properties.Second harmonic generation (SHG) is among the most ubiquitous methods used for probing surfaces and interfaces of centrosymmetric materials.[6] High sensitivity to the surface and thin film properties arises from SHG being prohibited in the electric dipole approximation in the volume of a centrosymmetric medium. As a result it is generated basically at surfaces and interfaces where the central symmetry is broken. Moreover one can break the inversion symmetry by an external influence such as electric and magnetic field causing so-called field induced second harmonic generation. [7][8][9] It has been demonstrated recently both theoretically and experimentally [10,11] that DC electric current flowing in the plane of a centrosymetric semiconductor can break the symmetry of the electron density distribution, resulting in current-induced SHG (CSHG) which can overwhelm conventional electric-field-induced mechanism if the conductivity of the probed material is sufficiently high. Moreover, theoretical predictions[11] made almost a decade before the advent of graphene demonstrate the possibility of the SHG enhancement by 1∼2 orders of magnitude in case of ballistic electron transport and in case of two-dimensional nature of the investigated electron system. In this paper we report the first investigation of current-induced second harmonic generation in multilayer graphene under ambient conditions...

An ultrathin nonlinear optical (NLO) organic surface composed of numerous self-assembled frustum-shaped whispering-gallery-mode resonators displays both two-photon luminescence and second-harmonic-generation signals. A super-second-order increase of the NLO intensity with respect to pump power confirms the microlasing action and practical usefulness of the NLO organic surfaces.

For what is to our knowledge the first time, electric-field-induced optical second-harmonic generation (SHG) is studied at the Si-SiO(2) interface by the use of a metal-oxide-semiconductor (MOS) structure. The crystallographic anisotropy of this phenomenon is studied for MOS structures. Experimental results indicate that the MOS technique of dc electric-field application to the Si-SiO(2) interface can be effectively used for studying electroinduced effects on SHG.