Application of geometric phase techniques to stellar interferometry

In stellar interferometry the fringe visibility can be measured by modulating the optical path difference between the two arms of an interferometer. This approach yields accurate estimates of the fringe visibility only if the bandwidth is small, and this limits the sensitivity of the technique. We propose using a geometric phase modulator that is achromatic and does not suffer from bandwidth restrictions. Fringe detectors using geometric phase modulation have the potential of greatly increasing the sensitivity of optical stellar interferometers.