The topological properties of an object, associated with an integer called the topological
invariant, are global features that cannot change continuously but only through abrupt …

Photonic Time-Crystals (PTCs) are materials in which the refractive index varies periodically
and abruptly in time. This medium exhibits unusual properties such as momentum bands …

Time reflection is a uniform inversion of the temporal evolution of a signal, which arises
when an abrupt change in the properties of the host material occurs uniformly in space. At …

Photonic time crystals are artificial materials whose electromagnetic properties are uniform
in space but periodically vary in time. The synthesis of these materials and experimental …

Gratings which are in apparent motion reveal some startling properties for classical
radiation, especially for luminal gratings traveling at or around the speed of light. We show …

For optics, like semiconductor heterostructures, the interfaces and inhomogeneities in
materials can manipulate optical waves and fields. Numerous photonic devices and …

Here we present a roadmap on Photonic metasurfaces. This document consists of a number
of perspective articles on different applications, challenge areas or technologies underlying …

We present an experimental study of optical time-refraction caused by time-interfaces as
short as a single optical cycle. Specifically, we study the propagation of a probe pulse …

Recent advances in ultrafast, large-modulation photonic materials have opened the door to
many new areas of research. One specific example is the exciting prospect of photonic time …

Time reflection and refraction are temporal analogies of the spatial boundary effects derived
from Fermat's principle. They occur when classical waves strike a time boundary where an …