  We demonstrate a photonic crystal nanocavity laser essentially driven by a
self-assembled InAs/GaAs single quantum dot gain. The investigated nanocavities
contain only 0.4 quantum dots on an average; an ultra-low density quantum dot
sample (1.5 x 108 cm-2) is used so that a single quantum dot can be isolated
from the surrounding quantum dots. Laser oscillation begins at a pump power of
42 nW under resonant condition, while the far-detuning conditions require ~145
nW for lasing. This spectral detuning dependence of laser threshold indicates
substantial contribution of the single quantum dot to the total gain. Moreover,
photon correlation measurements show a distinct transition from anti-bunching
to Poissonian via bunching with the increase of the excitation power, which is
also an evidence of laser oscillation with the single quantum dot.
