ROOM-TEMPERATURE TESTS OF AN OPTICAL TRANSDUCER FOR RESONANT GRAVITATIONAL-WAVE DETECTORS

A two-oscillator transducer incorporating a laser-illuminated Fabry-Perot cavity with a finesse of 77,500 and a power dissipation of 1.2 mu W was tested at room temperature. The energy of the last resonator with a mass of 1.25 g was measured to be k(B)T within 8%, and no back action from the sensor could be detected. The lowest value of the noise measured away from resonance was 1.0 x 10(-15) m/root Hz, and the electronic noise was 3.2 x 10(-17) m/root Hz. That transducer is designed for a 2400-kg gravitational wave antenna operating at cryogenic temperatures. At 4.2 K and for mechanical quality factors of 3 x 10(6), the measured thermal and electronic noise levels would translate into a sensitivity in h equal to 7.0 x 10(-19) and 1.5 x 10(-19), respectively.