High resolution adaptive optics using an interference phase loop

Abstract

The Interference Phase Loop is an interferometer with feedback of the output intensity to a phase modulator in one of the inteferometer arms. When a spatial optical phase modulator is used, the modulator phase distribution approximates to the conjugate of the spatial phase distribution in the interferometer, and so the device has potential for application in adaptive optics. We have implemented an interference phase loop using a high-resolution liquid crystal spatial light modulator (PAL-SLM) and a common path radial shearing interferometer. We show how the system can be analysed in simple terms, derive some design and operating criteria, and demonstrate diffraction-limited real-time aberration correction of arbitrary input wavefronts using the system. Because of the nature of the interferometer used, our system has the potential to operate in white light.