Quasi-resonant nonlinear absorption for optical power limiting: solgel-processed Er3+-doped multicomponent silica glass

We demonstrate optical power limiting by what we believe to be a new mechan ism of nonlinear absorption, which involves a quasi-resonant ground-state a bsorption that is either phonon assisted or assisted by the presence of def ect sites (tail absorption). Such a mechanism provides high transmittance a t low intensity yet optical limiting under cw conditions. The sample used w as a novel solgel-processed Er3+-doped multicomponent silica glass. in this system the nonlinear absorption process is achieved because the resonant e xcited-state (I-4(13/2) --> S-4(3/2)) absorption cross section is larger th an the quasiresonant ground-state (I-4(15/2) --> I-4(9/2)) absorption cross section. (C) 2000 Optical Society of America OCIS codes: 160.5690, 230.115 0, 300.1030.