Power limiting property of nano-sized
BaFe12O9 and Cr2O3 organosols
Pengfei Wu a, D. V. G. L. N. Rao*, a, Brian R. Kimballb, Masato Nakashimab, Barry S. DeCristofanob, Bingsuo Zouc
aDepartment of Physics, University of Massachusetts,
Boston, MA 02125 USA bMaterial Science Team, U. S. Army Soldier Systems Center, Natick, MA 01760 USA cSchool of Chemistry and Biochemistry, Georgia Institute of Technology Atlanta, GA 30332 USA
Nano-sized materials which exhibit large and fast third-order nonlinearities due to quantum confinement effect is attracting much attention recently. Large ratio of surface atoms to bulk atoms in nano-particles results in enhancement of optical nonlinearity. As such the surface chemical modification becomes more important for the optical property of the nano-materials. The synthesis by means of surface chemistry is a new direction to obtain novel nano-sized materials with surface coating. The micro-emulsion method is an example for synthesizing nanoparticles of core-shell structure by modifying a given size-quantized nanoparticles with surfactant molecules. These composite nanoparticles have been proved experimentally to exhibit some new features such as a tunable optical gap and spatial separation of the carriers, etc. In this article, we present results of optical power limiting property of two new nano-sized materials of BaFe12O9 and Cr2O3 organosols, which are synthesized by using micro-emulsion method. Both materials show good optical power limiting feature by using 532 nm Nd:YAG nanosecond frequency-doubled pulse laser. For BaFe12O9 nano-material, the limiting threshold of input fluence is about 10-6 J, and the transmission decreases to 50% of initial value when the input fluence increases to 10-5 J. The limiting threshold of input fluence for Cr2O3 material is about 4*10-6 J. We believe the power limiting features for these nano-sized materials are due to the absorption of a new excited state.
D. V. G. L. N. Rao
Department of Physics, University of Massachusetts
100 Morrissey Blvd.
Boston, MA 02125-3393 USA