  The dark solitons observed in a large variety of nonlinear media are unstable
against the modulational (snake) instabilities and can break in vortex streets.
This behavior has been investigated in nonlinear optical crystals and ultracold
atomic gases. However, a deep characterization of this phenomenon is still
missing. In a resonantly pumped 2D polariton superfluid, we use an all-optical
imprinting technique together with the bistability of the polariton system to
create dark solitons in confined channels. Due to the snake instabilities, the
solitons are unstable and break in arrays of vortex streets whose dynamical
evolution is frozen by the pump-induced confining potential, allowing their
direct observation in our system. A deep quantitative study shows that the
vortex street period is proportional to the quantum fluid healing length, in
agreement with the theoretical predictions. Finally, the full control achieved
on the soliton patterns is exploited to give a proof of principle of an
efficient, ultra-fast, analog, all-optical maze solving machine in this
photonic platform.
