Bistable emission of a black-body radiator

Bistable black-body emission is reported from resonantly excited Er3+,Yb3+:Y2O3Er3+,Yb3+:Y2O3 nanopowders. A simple model based on thermo-optic nonlinear response in the strongly scattering random medium explains the observed behavior.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69863/2/APPLAB-85-23-5517-1.pd

Self Assembly and Optical Properties of Dendrimer Nanocomposite Multilayers

Ultrathin multilayers are important for electrical and optical devices, as well as for immunoassays, artificial organs, and for controlling surface properties. The construction of ultrathin multilayer films by electrostatic layer-by-layer deposition proved to be a popular and successful method to create films with a range of electrical, optical, and biological properties. Dendrimer nanocomposites (DNCs) form highly uniform hybrid (inorganic–organic) nanoparticles with controlled composition and architecture. In this work, the fabrication, characterization, and optical properties of ultrathin dendrimer/poly(styrene sulfonate) (PSS) and silver–DNC/PSS nanocomposite multilayers using layer-by-layer (LbL) electrostatic assembly techniques are described. UV-vis spectra of the multilayers were found to be a combination of electronic transitions of the surface plasmon peaks, and the regular frequency modulations attributable to the multilayered film structure. The modulations appeared as the consequence of the highly regular and non-intermixed multilayer growth as a function of the resulting structure. A simple model to explain the experimental data is presented. Use of DNCs in multilayers results in abrupt, flat, and uniform interfaces.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/56176/1/1032_ftp.pd

Multiple scattering and nonlinear thermal emission of Yb3+,Yb3+, Er3+:Y2O3Er3+:Y2O3 nanopowders

Radiation transport and multiple scattering calculations are presented and compared with experimental observations to characterize light attenuation in high emissivity nanopowders irradiated with low power laser light at room temperature, and to explain the associated white light emission and the onset of melting. Using radiation tuned to an absorption resonance of Yb3+Yb3+ dopants in Y2O3Y2O3 nanopowder, we observed the onset of intense blackbody emission above a well-defined intensity threshold. Local melting of the compact above threshold leads to the formation of single crystal microtubes. Evidence is provided to show that two-flux transport theory and diffusion theory both significantly underestimate the absorption due to dependent, multiple scattering and that the threshold for the thermal runaway process responsible for this behavior is very sensitive to porosity of the random medium. © 2004 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70611/2/JAPIAU-95-8-4069-1.pd