Physics Seminar:Ceyhun Bulutay, April 28 2010, FENS L035, 13:40 p.m.

    Interaction of light with silicon & germanium nanocrystals at the atomistic level

 
                                                     Ceyhun Bulutay
                                  Fizik Bölümü, Bilkent Üniversitesi, Ankara

Abstract: Silicon is abundant and easy to fabricate, but it is barely luminescent. Germanium is slightly better, but still poor for optics. However, their nanocrystalline forms have improved and tunable optical properties, therefore intensive research efforts are dedicated for their photonic and photovoltaic applications. In this talk, I shall review our theoretical studies over the past five years, on the interaction of light with silicon and germanium nanocrystals of few nanometers in diameter embedded in an oxide host matrix. For an atomistic level understanding, we have developed a pseudopotential electronic structure tool that can solve tens of thousand-atom structures. Using this approach, first we have modeled two important non-radiative Coulomb processes: Auger recombination and carrier multiplication. On the light-matter interaction in Si and Ge nanocrystals, we have studied the linear and third-order nonlinear optical properties as well as the electroabsorption under a strong Stark field. The agreement of our results with experiment is quite satisfactory when excitonic effects are included, and even better if the spin-orbit coupling is also accounted. Finally, on the quantum optics in these nanocrystals, I shall talk about our recent efforts on the coherent population transfer based on the stimulated Raman adiabatic passage technique.

Biography: Ceyhun Bulutay received his PhD degree in 1997 from Middle East Technical University working with Prof. Mehmet Tomak on the computational many-body physics of two- and three-dimensional electron liquids. He was a postdoctoral researcher for one year at the University of California, Santa Barbara, followed by two-years at the University of Essex. Since September 2000, he is with the Department of Physics of Bilkent University. His research is on the computational semiconductor physics and more specifically their optical properties, carrier dynamics and atomistic structural properties.


Wednesday,  April 28 2010, FENS L035, at 13:40 p.m.