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Fostering Excellence
in Photonics and Quantum Science
at the University of Warsaw

Newsletter: Second Issue, March 2014

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Workshop on Molecular beam epitaxy

The workshop on “Molecular beam epitaxy” was organized between 16.09.2013 and 15.10.2013 at the Faculty of Physics, University of Warsaw. We hosted two lecturer - trainers - dr Carsten Kruse from Univerity of Bremen (Germany) and prof. Marek Potemski from Grenoble High Magnetic Field Laboratory (France). Dr Carsten Kruse realized practical exercises on substrate preparation for epitaxy, growth of photonic structures, and growth of low dimensional structures based on II-VI semiconductor compounds. Several clean-room and growth procedures trained with dr. Carsten Kruse were performed at University of Warsaw for the first time. They will be very important for research activity of workers participating in the project. Using ultra-pure materials prepared for the workshop (in particular zinc and magnesium), we have grown several microcavties and structures containing quantum dots. One day of dr. Carsten Kruse stay was devoted to lectures, seminars and discussions on epitaxy. Practical exercises planed by dr. Kruse were intensively continued during the workshop. The practical activities were coordinated by Wojciech Pacuski. Second lecturer, prof. Marek Potemski, realized more theoretical part of the workshop, with many discussions, seminars and one big lecture. In particular the vivid discussions on the role of solitary magnetic dopants in quantum dots gave ideas on new research methodologies and techniques. We discussed the research progress, shared experimental data. The seminars and discussions were chaired by prof. Andrzej Golnik. The new ideas were immediately tested and a new growth processes were done.

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Photonic Fibers I

The session on the topic Photonic Fibers I - “Nonlinear microstructured optical fibres” was organized by PhoQuS@UW in the framework of 15th Conference on Optical Fibers and Their Applications in Białystok – Lipowy Most between 29.01 and 1.02.2014. It consisted of 3 invited presentations given by scientists from three European research groups working in the domain of photonic crystal fibers. Every invited talk was planned for 30 min. The presentations were given by A. Heidt from University of Southampton, United Kingdom, U. Møller from Tech. Univ. of Denmark, Denmark and M. H. Frosz from Max Planck Institute for the Science of Light, Germany. This session was chaired by Ryszard Buczyński.

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Plasmonic Group

Plasmonic Group consisting of Tomasz Szoplik, Tomasz Stefaniuk and Piotr Wróbel, is active in simulation, fabrication and characterization of plasmonic nanostructures such as probes for scanning near-field optical microscope (SNOM), single and multilayer metal-dielectric plasmonic lenses, and structured metal films with application in photovoltaics. Since 2007 the Group has been involved in development of high resolution probes for SNOM. Together with Dr. Tomasz J. Antosiewicz, a former Group member, we proposed the first exact description of SNOM probe radiation that fully corresponds to experimental measurements. Then, we proposed and fabricated aperture, tapered-fiber, metal-coated SNOM probes with corrugated core-metal surface which increases energy throughput. More recently, we proposed and simulated properties of an aperture, tapered-fiber, metal-coated probe with internal azimuthally polarized illumination which concentrates longitudinal component of the magnetic field of light. The probe may serve for measurements of magnetic response of metamaterials. The Group is equipped with a fabrication tool (e-beam evaporator Lesker PVD75) as well as characterization devices such as scanning SNOM, AFM, STM, and electron microscopes. Functionality of the e-beam evaporator is enhanced with specially designed and built rotating and temperature-controlled sample holders. Performance of the commercial SNOM is improved with additional multiwavelength illumination system designed for transmission mode of work. Current research of the Plasmonic Group is oriented towards the following topics: 1. Design, fabrication and characterization of plasmonic nanolenses which in the far-field focus visible light to regions with full-width at half-maximum smaller than half a wavelength. The multilayer nanolenses are composed of two layers of metal: the output layer has concentric grooves or slits and the other forms Fabry-Perot resonator giving nearly 80% transmission. The metal films are separated with two dielectric layers: the input one serves as antireflecting coating while the other as metal separator. 2. Design, fabrication and characterization of plasmonic nontransparent metal cathodes for photovoltaics. Passage of a photon through a thin solar cells lasts about one femtosecond. To increase the probability of generation electron-hole pair, light should be trapped and density of electric field of light should be enhanced. This is achieved due to plasmonic effects on nanostructured surface of thin polymer solar cells. 3. Studies on morphological, optical and electrical properties of thin metal films. Smoothness of metal surface depends on a wetting interlayer used to control adhesion between metal and substrate particles in the evaporation process. Several wetting layers are tested to choose the ones which prevent island deposition and reduce specific resistivity of films at the same time. The Group collaborates with Prof. Pierre Chavel, Institut d’Optique Graduate School, Palaiseau, France, in the field of modelling and characterization of micro- and nano-optical devices and systems. Metal-dielectric nanoscale photonic devices support plasmon-polariton surface waves what results in novel functionalities such as superresolution and localized surface plasmon resonances useful in sensors. The second foreign partner is Prof. Concita Sibilia, University of Rome La Sapienza, Italy. Our contacts have been initiated under COST Action P11 and resulted in a book “Photonic Crystals: Physics and Technology”, C. Sibilia, T.M. Benson, M. Marciniak, T. Szoplik, Editors. (Springer, Milano, 2008). At present, Prof. Sibilia shares our interest in asymmetric transmission of terahertz radiation through periodic metal structures.

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Quantum information theory group

Quantum Information Theory group consists of Rafał Demkowicz Dobrzański and three PhD students - Jan Kołodyński, Marcin Jarzyna, and Tomasz Kaftal. Research interests of the Group cover a broad spectrum ranging from quantum cryptography, communication and computation problems with special focus on the subject of quantum metrology. They develop theoretical tools, which can be applied when solving quantum estimation tasks and designing required protocols. One of the aims is to build such techniques that can be efficiently applied when analyzing modern quantum-enhanced metrological experiments of atomic spectroscopy, quantum magnetometry and optical interferometry such as gravitational waves detection or atomic clock calibration. Fundamental bounds on maximal possible quantum enhancement that can be achieved in quantum metrological protocols operating in realistic environments have been derived. The derived bounds allow to understand the regime where quantum entanglement is helpful in boosting measurement precision and set a benchmark for experimental implementations of quantum enhanced protocols. In particular it has been shown that the quantum enhancement obtained recently in the GEO600 gravitational wave observatory using squeezed vacuum states is operating very close to the fundamental bound. R. Demkowicz-Dobrzanski is the leader of the Warsaw node of the SIQS (Simulators and Interfaces with Quantum Systems) FP7 Collaborative project 2013-2016. Within the project the group works on problems of quantum enhanced sensing, in particular metrology with multiparticle entangled states.

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