We have constructed and tested a laser interferometer transducer for a long, wideband, laser-linked gravitational radiation antenna. Photon-noise-limited performance was achieved using 80 µW from a single mode Spectra-Physics 119 laser in a modified Michelson interferometer on a vibration isolation table in a quiet room. A piezoelectric driver on one of the interferometer mirrors was used to generate subangstrom (3 × 10-14-m) vibrations of known amplitude. The measured displacement sensitivity of the system in the kilohertz region was 1.3 × 10-14m/Hz1/2, which compares well with the calculated photon noise limit of 1.06 × 10-14 m/Hz1/2. This is the smallest vibrational displacement measured directly with a laser to date.
G. E. Moss, L. R. Miller, and R. L. Forward, "Photon-Noise-Limited Laser Transducer for Gravitational Antenna," Appl. Opt. 10, 2495-2498 (1971)