Optical transducer prototype for gravitational-wave bar detectors

A prototype resonant transducer based on a Fabry-Perot optical cavity has been developed. The resonant mass carries one of the mirrors of the Fabry-Perot cavity, while the other mirror is attached to the bar detector. If a Nd:YAG laser is frequency-locked to this cavity, one could then measure small variations in the distance between the mirrors by comparing the laser light frequency to the characteristic frequency of a second Fabry-Perot cavity. This optical transducer prototype could theoretically operate as a single-quantum-limited device thereby bringing the bar detector to its maximum sensitivity. Preliminary room temperature tests of this prototype are reported in this paper.