Towards practical wavefront sensing at the fundamental information limit

The performance of adaptive optics systems, such as for astronomical telescopes, is often limited by the available light for wavefront sensing. The efficiency of the wavefront sensor is therefore of vital importance. We have recently used a Fisher information approach to derive a fundamental limit for the measurement of wavefront phase for adaptive optics systems at low light levels. The limit, which arises from the quantized nature of light, suggests that it may be possible for adaptive optics systems to operate at light levels close to the one photon per correction mode.