AUTOMATIC ALIGNMENT-CONTROL SYSTEM FOR A SUSPENDED FABRY-PEROT CAVITY

In interferometric gravitational-wave detectors, most of the optical c omponents are suspended by wires so that they are isolated from all ki nds of forces except gravity. The requirement for the alignment of opt ical components to the laser beam is crucial. We have demonstrated a s ervo system developed for a Fabry-Perot cavity whose mirrors are suspe nded independently. We use mechanical modulation and a lock-in detecti on method to detect any misalignment. This system directly detects the relation between the axis of the laser beam and the axis of the cavit y and automatically aligns the cavity to the laser beam. We confirmed that the intensity of the reflected light from the suspended Fabry-Per ot cavity can be minimized with this system. Automated control of the alignment of the large-scale detectors is also discussed.