Thursday July 7, 2005
2 PM - 3:30 PM
ENG Z-50 Auditorium

Office Hours:
Thursday July 7, 2005
3:30 PM - 4 PM
ENG B-18

"Vibronic excitation of single molecules: A new technique for studies in chemical physics and quantum optics"
Prof. Alper Kiraz
Koc University

In this talk, the results of our experiments at cryogenic temperatures on single dye molecules will be presented. The fluorescence of single molecules was first detected at cryogenic temperatures using narrow bandwidth excitation of the purely electronic zero-phonon line. While this type of experiments yields a detailed insight into the interaction between a chromophore and its environment, its application is restricted to very few systems. In our experiments, we have realized the vibronic excitation scheme where we made use of the broad width of vibronic molecular transitions. Excitation of these bands allow for the observation of the extremely narrow, nearly lifetime limited zero-phonon line emission. By monitoring the spectral position of the zero phonon line emission, important hints on conformational changes can be observed. This technique can be applied to unravel protein folding mechanisms. The nearly transform limited zero-phonon line emission of a single molecule can also be used as a single photon source for applications in quantum information science. These applications rely heavily on the two-photon interference phenomenon. When two indistinguishable photons arrive at a 50/50 beam spliter from different input channels, they will leave the beam splitter through the same output channel. In our experiments, we have demonstrated this phenomenon by directing the zero-phonon line emission of a single molecule to a Michelson interferometer and performing coincidence detection experiments at the output of the interferometer. We have observed a lack of coincidence counts as the signature of two-photon interference.