Deployment of nanometer-sized semiconductor quantum dots (QDs) in the active region of
photonic devices such as lasers, semiconductor optical amplifiers (SOA's), photo-detectors etc.
for the next generation communication systems offers unique characteristics such as
temperature-insensitivity, high optical output power, high speed operation, wide-band
characteristics etc.; not commonly attainable in the conventional design approaches. Despite
more than twenty years of research on the electronic and optical properties of QDs, still
challenges remain such as wavelength tuning to 1.5μm regime and achieving isotropic
polarization from these compressively strained nano-structures etc. We apply atomistic modeling
techniques to study the electronic structure, optical spectra and polarization response of QDs and
engineer them for the desired properties. This talk will provide a brief overview of the QD based
photonic devices and their main challenges, followed by our recent experimental and theoretical
work to overcome these problems by structural and strain engineering of QDs to enable new
routes towards future photonic devices.
Muhammad Usman is currently working at Tyndall National Institute, Ireland as a researcher,
after graduating with a PhD degree in Electrical Engineering from Purdue University, Indiana,
USA in August 2010. Tyndall National Institute is one of the leading European research centers
that specializes in all aspects of Information, Communications, and Technology (ICT) research
and hosts about 420 researchers as full time staff members, graduate students, and industrial
visitors. Broadly speaking, Usman's research focuses on improving the efficiency of
photovoltaics as renewable and economical energy resources, wavelength engineering by novel
materials and confinement techniques for Infrared range devices, and realization of quantum
information through coupled quantum dots. He is a member of the American Physical Society
(APS), Material Research Society (MRS), Institute of Electrical and Electronics Engineers
(IEEE), and serves on the editorial board of the American Journal of Condensed Matter Physics
(AJCMP). He is also closely affiliated and an active contributor of the National Science
Foundation (NSF) funded Network for Computational Nanotechnology (NCN) and its cyberinfrastructure
Presenter's website: http://web.ics.purdue.edu/~usman
Full abstract here: http://events.thayer.dartmouth.edu/index.php?com=detail&eID=1330&year=2012&month=03
M. Usman, "In-plane polarization anisotropy of ground state optical intensity in InAs/GaAs quantum dots", Journal of Applied Physics 110, 094512, (2011);
M. Usman, S. Heck, E. Clarke, P. Spencer, H. Ryu, R. Murray, G. Klimeck, "Experimental and theoretical study of polarization-dependent optical transitions in InAs quantum dots at telecommunication-wavelengths (1300-1500 nm)", Journal of Applied Physics 109, 104510 (2011);
M. Usman, T. Inoue, Y. Harda, G. Klimeck, T. Kita, "Experimental and atomistic theoretical study of degree of polarization from multilayer InAs/GaAs quantum dot stacks", Physical Review B 84, 115321 (2011);
Researchers should cite this work as follows:
- M. Usman, "Quantum Dot based Photonic Devices", Quantum/Nano-Physics Seminar, Department of Physics and Astronomy, Dartmouth College, Hanover, NH, 03755, USA; March 9, 2012.
Dartmouth College, Hanover, NH
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