extracting random effect standard deviation

Hello,

How can I 'extract' the value of a random effect's standard deviation
from an lmer model?
This number is (a rather important) part of the usual lmer() output
but I cannot figure out anywhere in str(lmer.model) where it can be
found!

I can get it from summary(lmer.model)@REmat[,4], but that 'extra' call
to summary is slowing down my program.

Obviously the model has this information in it somewhere because the
model listing contains it.
How can I get it out?

Thanks,
Daniel