--------------------------------------------------------------------
   COLLOQUIUM OF THE LABORATORY FOR COMPUTER DESIGN OF MATERIALS
                   School of Computational Sciences
                           (CSI 898-Sec 001)
--------------------------------------------------------------------
OPTICAL EXCITATIONS AND SPIN CONTROL IN SEMICONDUCTOR QUANTUM DOTS

                              Andrew Shabaev 
              Center for Computational Materials Science, 
               Naval Research Laboratory,Washington DC

Semiconductor quantum dots are nanometer scale structures with a discrete
energy spectrum that results from the confinement of carriers
(electrons and holes) within the dots. Technological advances open
an opportunity to control the size, shape and composition of quantum dots.
Quantum dots are often described as artificial atoms because some properties
of quantum dots are comparable to those of atoms including atomic-like
optical spectra with very sharp spectral lines. The linear excitation spectrum
of undoped quantum dots is that of a coupled electron-hole pair,
or exciton. Oscillator strengths of excitons exceed those in atoms making
them very attractive for a variety of nonlinear optical applications utilizing
the interference of coherent quantum states. The practical use of these
coherent
effects depends on their coherence lifetime. This is the time it takes for
the polarization of an exciton to lose its coherence with the optical field.
The spin polarization induced by the same field exists for a longer time.
Recently, it was proposed that the spin coherence time can be increased
by doping quantum dots with an extra electron. The ability to maintain and
control spin coherence for a substantially long period of time is extremely
important in spin coherent electronics, or spintronics. The combination of
strong
nonlinear optical properties with a long spin coherence time opens new
possibilities for a wide range of applications, from ultrafast magnetooptics
to quantum computation.
                        
                        Monday , November 22, 2004
                                  4:30 pm
              Room 206, Science & Tech. I, Fairfax Campus

Refreshments will be served at 4:15 PM.
----------------------------------------------------------------------
Find the schedule at http://www.scs.gmu.edu/lcdm/seminar/schedule.html
--------------------------------------------------------------------