The optical properties of metamaterials made by block copolymer self-assembly are tuned by structural and environmental variations. The plasma frequency red-shifts with increasing lattice constant and blue-shifts as the network filling fraction increases. Infiltration with dielectric liquids leads also to a red-shift of the plasma edge. A 300 nm-thick slab of gyroid-structured gold has a remarkable transmission of 20%.

The control of the optical activity and ellipticity of a medium has drawn considerable attention due to the recent developments in metamaterial design techniques and a deeper understanding of the light matter interaction in composite metallic structures. Indeed, recently proposed designs of metaatoms have enabled the realisation of materials with unprecedented chiral optical properties e.g. strong optical activity, broadband optical activity, and nondispersive zero ellipticity. Combining chiral metamaterials with nonlinear materials has opened up new possibilities in the field of nonlinear chirality as well as provided the foundation for switchable chiral devices. Furthermore, chirality together with hyperbolicity can be used to realise new exciting materials such as photonic topological insulators. In this review, we will outline the fundamental principles of chiral metamaterials and report on recent progress in providing the foundations for promising applications of switchable chiral metamaterials.

Metallic single gyroids, a new class of self-assembled nanoplasmonic metamaterials, are analyzed on the basis of a tri-helical metamaterial model. The physical mechanisms underlying the chiral optical behavior of the nanoplasmonic single gyroid are identified and it is shown that the optical chirality in this metallic structure is primarily determined by structural chirality and the connectivity of helices along the main cubic axes.

Electric control of coupling in hybrid graphene/metamaterial system enables strong selective modulation of light polarization.

Topological photonics has recently been proved a robust framework for manipulating light. Active topological photonic systems, in particular, enable richer fundamental physics by employing nonlinear light-matter interactions, thereby opening a new landscape for applications such as topological lasing. Here we propose an all-dielectric topological insulator laser scheme in telecommunication region based on semiconductor cavities formed by topologically distinct Kagome photonic crystals. Our theoretical results show that the proposed planar semiconductor Kagome lattice can lift degeneracy with geometrical perturbation and open broad photonic bandgaps, and valley-dependent edge states and topologically robust transport with subwavelength scale confinement are observed at the edge of the perturbed Kagome lattices with distinct valley Chern numbers. An interesting feature of the Kagome lattices is that it supports two different types of valley Hall edge modes, which enables the coexistence of high Q ring-resonator modes and lossy Fabry-Pérot resonator modes in the proposed topological cavities. Moreover, we explore pumping and lasing dynamics of the topological cavities by means of a four-level two-electron model and demonstrate that this model offers a powerful platform to investigate non-Hermitian topological laser cavities with arbitrary geometry. The proposed topological semiconductor scheme provides a new route to study non-Hermitian topological photonics and to develop integrated topological systems for robust light generation and transport.