Analysis of an active stabilization system for a holographic setup

An active stabilization system for a holographic setup based on detection of phase shift between the interference pattern and a reference hologram is described. Its basic feature is the possibility of operating for 0, pi or +/-pi/2 at will, always in a null-detection mode. The reference hologram may be a previously recorded permanent hologram or a real-time (even reversible) one. The use of the open loop response of the stabilization system is developed for analyzing its performance, which allows closer insight into parameters limiting Its behavior. The effects of different noise sources are analyzed in detail. The real-time effect in a positive resist is successfully employed for operating the stabilization setup for recording an improved grating in this material.