We present theoretical results that demonstrate a new technique that can be
used to improve the sensitivity of thermal noise measurements: intracavity
intensity stabilization. It is demonstrated that electro-optic feedback ca
n be used to reduce intracavity intensity fluctuations, and the consequent
radiation pressure fluctuations, by a factor of 2 below the quantum-noise l
imit. We show that this reduction is achievable in the presence of large cl
assic intensity fluctuations in the incident laser beam. The benefits of th
is scheme are a consequence of the sub-Poissonian intensity statistics of t
he field inside a feedback loop and the quantum nondemolition nature of rad
iation pressure noise as a readout system for the intracavity intensity flu
ctuations. (C) 1999 Optical Society of America. OCIS codes: 270.2500, 120.5
050, 120.7280.