Title: Coherent Spectroscopy of Quantum Dots: Experiments & Theory
Speaker: Dr. Madhuri Mukhopadhyay
Abstract: Coherence plays a crucial role in energy transfer dynamics in photosynthetic pigment proteins as well as their artificial analogues. Our studies using ultrafast 2D-optical spectroscopic technique, where the four wave mixing method has a control over the phase information, clearly reveals the phase evolution of phonons and exciton-phonon coupling in quantum dots. The 2D-spectra resolve the nature of the coherent phonon, comparing the ground state bleaching and stimulated emission. To view the coherent oscillation in additional dimension, we introduce third Fourier transform along the waiting time of 2Dspectra, which precisely shows the bounce back of phonon wave packets in 160 fs at the excited electronic potential. We also describe theoretically the decoherence in Rabi oscillation in single electron quantum dot, taking into account inherent damping in the system and deriving the Hamiltonian equation using Euler-Lagrange method. Using many body configuration interaction method as well first-principles calculations, we predict how the relative energy of coherent and incoherent states can be controlled through chemical doping and the possibilities of high nonlinear optical activities in graphene quantum dots.
References:
1. 3D spectroscopy of coherences in colloidal quantum dots (in manuscript) Mukhopadhyay, M.; Augulis , R.; Lenngren, N.; K.; Zidek, Zigmantas, D.; Pullerits, T. ( accepted for presentation in International Conference on Coherent Multidimensional Spectroscopy, 2012 http://www.mbiberlin.de/cmds2012/images/program_cmds2012.pdf )
2. Coherent artifact study of two dimensional spectral shearing interferometry Rhodes, M.; Mukhopadhyay, M. ; Birge, J.; and Rick TrebinoJournal of the Optical Society of America B, 2015, 32 (9), 18811888
3. Tweaking optical efficiency by altering interfacial atom stoichiometry in hetero structure nano crystal,Jose F. Aldana, Madhuri Mukhopadhyay , Benard Omogo, and Colin D. Heyes (inmanuscript)
4. Nature of blinking with variation of shell materials on CdTe core quantum dotMadhuri Mukhopadhyay, Feng Gao, Benard Omogo, and Colin D. Heyes (in manuscript)
5. Linear and Nonlinear Optical Properties of Graphene Quantum Dots:A Computational Study,Yamijala S. SRKC; Mukhopadhyay, M; Pati, S. K.J. Phys. Chem. C, 2015, 119, 12079 − 12087
6. Rabi type oscillations in damped two dimensional single electron quantum dots,Mukhopadhyay, M .; Hazra, R.K.; Ghosh, M.; Mukherjee, S.; Bhattacharyya, S.P Cent. Eur. J. Phys, 2012, 10(4) , 983988
7. Tuning the Optically Bright and Dark States of Doped Graphene Quantum DotsMukhopadhyay. M. ; Pandey, B.; Pati, S. K. Phys. Rev. App. 2016, 6, 044014