A relatively simple 'all-optical' system, called a self-referenced interference phase loop (IPL), is presented for measuring spatial and temporal phase fluctuations over an optical wavefront, and also adaptively correcting that wavefront and/or generating a conjugate wave. It is shown that this system can unambiguously (with no phase quadrant ambiguity) estimate and compensate phase in real time over multiple Tr radians of dynamic range/ and is essentially unaffected by simultaneous wave amplitude variations. Furthermore, this system requires no external reference wavefront and can operate on partially coherent and multispectral (i. e, "white light") wavefronts, in which case it estimates and compensates optical-path-distance errors. In addition, the IPL readily lends itself to high resolution "all-optical" implementations containing thousands to millions of spatial resolution elements. The IPL can also be operated as a bistable array in optical information processing and computing applications.
Arthur D. Fisher,
"Self-referenced High Resolution Adaptive Wavefront Estimation And Compensation", Proc. SPIE 0551, Adaptive Optics, (16 January 1986); doi: 10.1117/12.949009; https://doi.org/10.1117/12.949009