Self-organized Metallic Nanotemplates Sayantani Ghosh, University of California – Merced, DMR Nano-materials exhibit properties distinctly different from those of their bulk counterparts, underlining the ideology that “small is different”. One popular type of nano-scale structures are quantum dots (QDs) – a few nanometer (10 -9 m) diameter artificial atoms with electronic and optical properties that can be tuned by alteration of the QD sizes. The questions of how the behavior of these QDs change when electronic or optical interactions are introduced between them have generated considerable interest and investigations in the recent years. We are using novel thermoplastic substrates with metallic coatings to develop self-organized nanostructured templates. Deposition of chemically synthesized QDs on these structures have demonstrated signatures that the QDs develop electronic dipolar couplings, leading to spectral red-shift and increased rates of recombination. 11 ns 3 ns In solution On metal & red-shifted A B C (A) Gold coated thermoplastic substrate showing the formation of self-organized micro- and nano-wrinkles. (B) CdSe QDs spin coated on the substrate show spectral red-shift of almost 10 nm compared to the emission in solution (red circle) in certain regions and this appears to follow the structural pattern of the metal wrinkles. This red-shift also appears localized and is not seen everywhere (example, blue circle) (C) Time-resolved measurements show faster decay rate in QDs on the metal structures.

Optical pulse evolution in optical fibers Sayantani Ghosh, University of California – Merced, DMR An optical fiber is an excellent system in which to observe the formation and evolution of temporally short light pulses. It enables one to experimentally validate mathematical models in nonlinear dynamics. Solitons and similaritons are two special kinds pulse shapes: the former travels along without changing its shape whereas the latter features self- similar behavior. We observe unique cooperative behavior between optical pulses, solitons in this case, as they shift in frequency due to propagation through an exciting class of optical fibers called photonic crystal fibers. Cross sectional views of a photonic crystal fiber Supercontinuum effect due to pulse propagation Cooperative spectral shifting of pulses

Enter Your Highlight Title Here Sayantani Ghosh, University of California – Merced, DMR UC Merced is building an undergraduate culture where research experience is strongly emphasized. The laser and detection system purchased through this grant has been made accessible to several undergraduate students in the Ghosh Lab. They are completing their senior thesis projects. This coming year we will incorporate this new laser system into our Physcis 160 Modern Physics Laboratory course. Junior year students will learn the basics of system operation and characterize numerous aspects of the output of the system. A large number of undergraduate researchers in the Ghosh Lab have been trained on the laser system purchased through this grant, and are engaged in senior research projects in varied disciplines which utilize this set-up. (Above, left to right): Anthony Grimes, Biology; Stephen Horabin, Bioengineering; Richard Inman, Physics; Christopher Ferri, Physics; Patricia Duggan, Management.