Insight into a new geometrical approach to beam fanning in BaTiO3

The fanning behavior of the two interacting laser beams in a double phase-c onjugate mirror (DPCM) obviously influences the characteristics of the mirr or. We present a two-dimensional experimental study and model of the beam-f anning patterns obtained in nominally undoped and cobalt-doped (20 parts in 10(6)) BaTiO3 samples. We propose a numerical method based on beam couplin g theory that allows us to determine, for each crystal, which directions wi ll develop significant fanning. We thus interpret the beam-fanning patterns by focusing on the influence of the incident beam's width and incidence an gle. The time evolution of the intensity in each of these directions is als o studied and modeled. This model has been applied to DPCM to enable both i ncident beams to generate fanning in a common direction, with good results in terms of response time, efficiency, and stability. (C) 2001 Optical Soci ety of America.