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When embedded in a microcavity, quantum dots (QD) are expected to interact with a confined optical mode only when there is an overlap in energy between the cavity resonance and the discrete excitonic transitions. However, experiments with self-assembled QDs have shown that the latter inherently exhibit a multi-excitonic background continuum, which couples efficiently to the mode and results in spurious light emission. Is this problem universal to all QD systems? The answer is no, as we have demonstrated using pyramidal QDs integrated into photonic crystal slab cavities.
For more details:
M. Calic, P. Gallo, M. Felici, K. A. Atlasov, B. Dwir, A. Rudra, G. Biasiol, L. Sorba, G. Tarel, V. Savona and E. Kapon, “Phonon-Mediated Coupling of InGaAs/GaAs Quantum-Dot Excitons to Photonic Crystal Cavities”, Phys. Rev. Lett. 106, 227402 (2011).
May 2010 : Polarization entangled photons from pyramidal QDs
Semiconductor quantum dots (QDs) have been proposed and demonstrated as a source of on demand polarization-entangled photons. We recently reported on the generation of entangled photons from highly symmetric, site-controlled QDs grown in inverted pyramids. The unique symmetry and exceptional uniformity of the pyramidal QDs provide significant potential for producing sources of triggered entangled photons from as-grown QDs without resorting to any of the post-processing steps customarily used in previous studies.
For more details: A. Mohan, M. Felici, P. Gallo, B. Dwir, A. Rudra, J. Faist, E. Kapon, “Titre”, Nature Photonics 4 302-306 2010 (- ).
April 2009 : Hybridization of electron and hole states in QD molecules
Hybridization of both electron and hole states in QD molecule was demonstrated for the first time using pyramidal QD molecule system. The hybridized the hole states in such structure induces switching of hole character as well as the emission polarization, which is of high interest for polarization-controlled QD photonic devices.
For more details: Q. Zhu, K. F. Karlsson, M. Byszewski, A. Rudra, E. Pelucchi, Z. B. He and E. Kapon, “Hybridization of Electron and Hole states in Semiconductor Quantum Dot Molecules”, Nature Photonics 4 329-33 2009
We demonstrated mode coupling in two coupled photonic-crystal cavities, showing that not only the resonant wavelength, but also the cavity loss, splits due to coupling. It is also shown that loss equalization of the coupled modes is necessary for efficient photon transfer between cavities.
For more details: K. A. Atlasov, K. F. Karlsson, A. Rudra, B. Dwir and E. Kapon, “Wavelength and loss splitting in directly coupled photonic-crystal defect microcavities”, Opt. Express 16 (20), 16255-16264 (2008)
August 2008: Positioning and alignment of DNA molecules
Electron-beam-induced lithography of organic films deposited on graphite substrates is employed for implementing positioning and alignment of triple- and double-stranded DNA molecules. Similar nano-templates based on such ”electrostatic traps” should be useful for producing a variety of nanoscale molecular or bioelectronic devices.
For more details: D. Klinov, K. Atlasov, A. Kotlyar, B. Dwir and E. Kapon, “DNA Nanopositioning and Alignment by Electron-Beam-Induced Surface Chemical Patterning”, Nano Letters. 7 (12), 3583-3587 (2007).
August 2008: Terahertz quantum cascade laser grown by MOVPE
THz quantum cascade lasers grown by metallorganic chemical vapor deposition (MOVPE), emitting photons of 90�m wavelength (3.3THz) are reported for the first time. Maximum operating temperature is 93K. The use of MOVPE in the growth of these complex nanostructures brings about new opportunities for studying their operation mechanisms and facilitating their manufacturing.
For more details: L. Sirigu, A. Rudra, E. Kapon, M.I. Amanti, J. Scalari and J. Faist, “A terahertz quantum cascade. laser grown by low-pressure metalorganic vapor phase epitaxy”, Appl. Phys. Lett. 92 , 181111 (2008).
August 2008: Integration of site-controlled quantum dots and photonic crystal cavities
A site-controlled InGaAs pyramidal quantum dot (QD) was integrated with an L3 photonic crystal membrane cavity. Evidence for deterministic coupling of the QD emission to the cavity mode is provided by optical spectroscopy and modeling. Such structures may form the basis for the integration of more QD systems with photonic nanostructures, for applications in quantum information processing and communications.
For more details: P. Gallo, M. Felici, B. Dwir, K.A. Atlasov, K.F. Karlsson, A. Rudra, A. Mohan, G. Biaisol, L. Sorba and E. Kapon, “Integration of site-controlled pyramidal quantum dots and photonic crystal membrane cavities”, Appl. Phys. Lett. 92 , 63101 (2008).
March 2007 : Scientific Omega Prize 2006 awarded to Martin H. Baier
The award was discerned to Dr. Martin H. Baier for his thesis entitled ”Correlated Photon Emission from Pyramidal Quantum Dot Heterostructures”, performed at LPN-EPFL and defended in 2005.