Keck Interferometer differential-phase planet-detection system requires a picometer accuracy, large (2 μm to 4 μm) amplitude optical path-length modulator that can operate at fairly high frequencies (250 Hz, 750 Hz, and 1250 Hz, a partial, triangular wave motion).
We have developed a gauge which monitors the amplitude of the motion of the path-length modulator and which is capable of reaching a sensitivity of at least 3 pm per sqrt(Hz) within a band width of 1 Hz at 250 Hz, 750 Hz, and 1250 Hz. Two of these gauges are built. The gauges are compared to each other while monitoring a common optical path-length modulator to determine their accuracy.
In this paper, the gauge construction details, the results of the gauge accuracy tests as well as the final path-length modulator performance details are presented.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.