Ol. Antipov et al., Dynamics of refractive-index changes in a Nd : YAG laser crystal under excitation of Nd3+ ions, J OPT SOC B, 16(7), 1999, pp. 1072-1079
The mechanism for refractive-index changes that accompany changes in popula
tion during pumping and amplification of an optical beam is studied in a Nd
:YAG laser crystal by both resonant four-wave mixing and interferometric te
chniques. It is found that these refractive-index changes (connected with t
he difference in polarizability of excited and unexcited Nd3+ ions) have tw
o components: a small noninertial component that accompanies an amplified o
ptical pulse and the major changes that are intensified with a delay time o
f similar to 3 mu s The latter effect is explained by population (or depopu
lation) of a higher-lying energy level (2)(F2)(5/2) of the 4f electron shel
l of Nd3+ ions, which has large polarizability in near-IR and visible light
. The real part of the nonlinear optical resonant susceptibility of the inv
ert;ed Nd:YAG caused by the refractive-index changes is also discussed. (C)
1999 Optical Society of America [S0740-3224(99)00407-5].