Orthogonally acting phase-locked loops operating at distinct, well-separated dither frequencies are used to automatically align (maximize output power) an argon ion pump laser, its pointing into a ring dye laser, and optimize a dye laser beam coupling into a single mode fiber of 4 micron core diameter. Such a system of feedback loops or combination of them is an ATOM (Alignment Through Orthogonal Maxima).
M. C. Rushford,
P. J. Kuzmenko,
"Pointing Alignment By Orthogonal Phase-Lock Feedback Loops", Proc. SPIE 0608, Optical Alignment III, (12 May 1986); doi: 10.1117/12.976190; https://doi.org/10.1117/12.976190