  This paper introduces a new approach to neuromorphic photonics in which
microcavities exhibiting strong exciton-photon interaction may serve as
building blocks of optical spiking neurons. The experimental results
demonstrate the intrinsic property of exciton-polaritons to resemble the Leaky
Integrate-and-Fire spiking mechanism. It is shown that exciton-polariton
microcavities when non-resonantly pumped with a pulsed laser exhibit
leaky-integration due to relaxation of the excitonic reservoir,
threshold-and-fire mechanism due to transition to Bose-Einstein condensate, and
resetting due to stimulated emission of photons. These effects, evidenced in
photoluminescence characteristics, arise within sub-ns timescales. The
presented approach provides means for energy-efficient ultrafast processing of
spike-like laser pulses at the level below 1 pJ/spike.
