  We demonstrate sequential lasing at two well-separated energies in a highly
photoexcited planar microcavity at room temperature. Two spatially overlapped
lasing states with distinct polarization properties appear at energies more
than 5 meV apart. Under a circularly polarized nonresonant 2 ps pulse
excitation, a sub-10-ps transient circularly polarized high-energy (HE) state
emerges within 10 ps after the pulse excitation. This HE state is followed by a
pulsed state that lasts for 20--50 ps at a low energy (LE) state. The HE state
is highly circularly polarized as a result of a spin-preserving stimulated
process, while the LE state shows a significantly reduced circular polarization
because of a diminishing spin imbalance.
