We demonstrate optical power limiting by what we believe to be a new mechanism of nonlinear absorption, which involves a quasi-resonant ground-state absorption that is either phonon assisted or assisted by the presence of defect sites (tail absorption). Such a mechanism provides high transmittance at low intensity yet optical limiting under cw conditions. The sample used was a novel solgel-processed Er<sup>3+</sup>-doped multicomponent silica glass. In this system the nonlinear absorption process is achieved because the resonant excited-state (<sup>4</sup><i>I</i><sub>13/2</sub> → <sup>4</sup><i>S</i><sub>3/2</sub>) absorption cross section is larger than the quasi-resonant ground-state (<sup>4</sup><i>I</i><sub>15/2</sub> → <sup>4</sup><i>I</i><sub>9/2</sub>) absorption cross section.
© 2000 Optical Society of America
Glauco S. Maciel, Abani Biswas, Christopher S. Friend, and Paras N. Prasad, "Quasi-Resonant Nonlinear Absorption for Optical Power Limiting: solgel-Processed Er3+-Doped Multicomponent Silica Glass," Appl. Opt. 39, 2433-2436 (2000)