  A new class of phenomena stemming from topological states of quantum matter
has recently found a variety of analogies in classical systems. Spin-locking
and one-way propagation have been shown to drastically alter our view on
scattering of electromagnetic waves, thus offering an unprecedented robustness
to defects and disorder. Despite these successes, bringing these new ideas to
practical grounds meets a number of serious limitations. In photonics, when it
is crucial to implement topological photonic devices on a chip, two major
challenges are associated with electromagnetic dissipation into heat and
out-of-plane radiation into free space. Both these mechanisms may destroy the
topological state and seriously affect the device performance. Here we
experimentally demonstrate that the topological order for light can be
implemented in all-dielectric on-chip prototype metasurfaces, which mitigate
the effect of Ohmic losses by using exclusively dielectric materials, and
reveal that coupling of the system to the radiative continuum does not affect
the topological properties. Spin-Hall effect of light for spin-polarized
topological edge states is revealed through near-field spectroscopy
measurements.
