  Valley photonic crystal is one type of photonic topological insulator, whose
realization only needs P-symmetry breaking. The domain wall between two
valley-contrasting photonic crystals support robust edge states which can wrap
around sharp corners without backscattering. Using the robust edge states, one
can achieve the pulse transmission. Here, using time-domain measurement in the
microwave regime, we show distortionless pulse transmission in a sharply bended
waveguide. An Omega-shaped waveguide with four 120-degree bends is constructed
with the domain wall between two valley photonic crystal slabs. Experimental
results show the progress of Gaussian pulse transmission without distortion,
and the full width at half maximum of the output signal was changed slightly in
the Omega-shaped waveguide. By measuring steady state electric field
distribution, we also confirmed the confined edge states without out-of-plane
radiation which benefits from the dispersion below the light line. Our work
provides a way for high-fidelity optical pulse signal transmission and develop
high-performance optical elements such as photonic circuits or optical delay
lines.
