We describe and demonstrate a method to control a detuned movable-mirror
Fabry-Perot cavity using radiation pressure in the presence of a strong optical
spring. At frequencies below the optical spring resonance, self-locking of the
cavity is achieved intrinsically by the optomechanical (OM) interaction between
the cavity field and the movable end mirror. The OM interaction results in a
high rigidity and reduced susceptibility of the mirror to external forces.
However, due to a finite delay time in the cavity, this enhanced rigidity is
accompanied by an anti-damping force, which destabilizes the cavity. The cavity
is stabilized by applying external feedback in a frequency band around the
optical spring resonance. The error signal is sensed in the amplitude
quadrature of the transmitted beam with a photodetector. An amplitude modulator
in the input path to the cavity modulates the light intensity to provide the
stabilizing radiation pressure force
