  We report on use of a radiation pressure induced restoring force, the optical
spring effect, to optically dilute the mechanical damping of a 1 gram suspended
mirror, which is then cooled by active feedback (cold damping). Optical
dilution relaxes the limit on cooling imposed by mechanical losses, allowing
the oscillator mode to reach a minimum temperature of 6.9 mK, a factor of
~40000 below the environmental temperature. A further advantage of the optical
spring effect is that it can increase the number of oscillations before
decoherence by several orders of magnitude. In the present experiment we infer
an increase in the dynamical lifetime of the state by a factor of ~200.
