  We resonantly inject polaritons into a microcavity and track them in time and
space as they feel a force due to the cavity gradient. This is an example of
"slow reflection," as the polaritons, which can be viewed as renormalized
photons, slow down to zero velocity and then move back in the opposite
direction. These measurements accurately measure the lifetime of the polaritons
in our samples, which is 180 $\pm$ 10 ps, corresponding to a cavity leakage
time of 135 ps and a cavity $Q$ of 320,000. Such long-lived polaritons
propagate millimeters in these wedge-shaped microcavities. Additionally, we
generate polaritons by two-photon excitation directly into the polariton
states, allowing the possibility of modulation of the two-photon absorption by
a polariton condensate.
