  Light propagation in periodic environments is often associated with a number
of interesting and potentially useful processes. If a crystalline optical
potential is also linearly ramped, light can undergo periodic Bloch
oscillations, a direct outcome of localized Wannier-Stark states and their
equidistant eigenvalue spectrum. Even though these effects have been
extensively explored in conservative settings, this is by no means the case in
non-Hermitian photonic lattices encompassing both amplification and
attenuation. Quite recently, Bloch oscillations have been predicted in
parity-time-symmetric structures involving gain and loss in a balanced fashion.
While in a complex bulk medium, one intuitively expects that light will
typically follow the path of highest amplification, in a periodic system this
behavior can be substantially altered by the underlying band structure. Here,
we report the first experimental observation of Bloch oscillations in
parity-time-symmetric mesh lattices. We show that these revivals exhibit
unusual properties like secondary emissions and resonant restoration of PT
symmetry. In addition, we present a versatile method for reconstructing the
real and imaginary components of the band structure by directly monitoring the
light evolution during a cycle of these oscillations.
