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 , which compares well with the calculated photon noise limit of . This is the smallest vibrational displacement measured directly with a laser to date.
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