Wydział Fizyki UW > Badania > Seminaria i konwersatoria > Seminarium Optyczne

Seminarium Optyczne

2006/2007 | 2007/2008 | 2008/2009 | 2009/2010 | 2010/2011 | 2011/2012 | 2012/2013 | 2013/2014 | 2014/2015 | 2015/2016 | 2016/2017 | 2017/2018 | 2018/2019 | 2019/2020 | 2020/2021 | 2021/2022 | 2022/2023 | 2023/2024 | 2024/2025 | Seminarium na YouTube

RSS

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

Piotr Deuar (IF PAN)

Scalar field dark matter: a BEC with a galaxy-size wavelength

I will introduce the topic of scalar field dark matter, which is actually quite relevant for lovers of Bose quantum gases and classical wave fields, and then tell a bit about our preliminary investigations with collaborators at Newcastle University into the nonequilibrium dynamics of a dark matter halo.

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

Emilia Witkowska (IF PAN)

Spin chains and squeezing: simple theoretical results

Entanglement in systems with single-particle control is a well-established resource of modern quantum technology. Spin-squeezing is a great example of such. Applied in an optical lattice clock it can reduce the statistical uncertainty of spectroscopic measurements.During the seminar, I will consider the dynamic generation of spin squeezing in spin chains. I will show how anisotropic interactions and inhomogeneous magnetic fields generate scalable spin squeezing when their magnitudes are sufficiently small, but not negligible. The simple models for collective spin will be shown to describe the dynamics effectively. I will also discuss the effect of nonuniform filling caused by hole doping, at a microscopic level, demonstrating their limiting role in the dynamics and scaling.

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

Joanna Jankowska (Wydział Chemii UW)

Unidirectional molecular rotary motor with remotely-switchable rotation direction

Light-driven rotary motors allow direct transformation of light energy into unidirectional rotary motion at the nanoscale, giving rise to countless emerging applications in molecular engineering. The key feature enabling the unidirectional rotation and controlling its direction is the motor chirality, an inherently chemical factor, hard to modify postsynthetically. Here we propose a new molecular rotary motor architecture, E-motor, in which the motor operation direction can be switched in situ, without the need for chemical modification of the system structure. This effect is achieved by application of an external electric-field pulse, and is intended to provide means for chirality control in motors deposited on a surface. Our study relies on quantum-chemical calculations and nonadiabatic molecular dynamics simulations performed for a specifically-tailored system, PFCN, designed to provide illustration for the proposed new motor type. We show that the model system’s chirality and, hence, its operation direction, depends on orientation of a covalently bound polar switching unit, which can be controlled with an external electric field. At the same time, the proposed system manifests all characteristic photophysical properties of a unidirectional molecular motor, and its set chirality is preserved, i.e., it is thermally and optically stable during the regular motor operation in the absence of the electric field.

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

Piotr Wasylczyk (IFD UW)

How to pursue you dreams in the free time at FUW, feel great... and fail

I will present a few projects in biomedical engineering – not necessarily directly optics-related – that used the knowledge and expertise of the FUW Division of Optics and ended with different outcomes.

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

Mariusz Gajda (IF PAN)

From quantum droplets to supersolids of ultracold atoms

Ultracold atoms, since the first achievement of Bose-Einstein condensation in 1995, have proven to be an exceptionally versatile platform for studying a wide range of physical phenomena. These include nonlinear effects, superfluidity, quantized vortices, quantum magnetism, many-body correlations, localization effects, or exotic Hubbard systems, to name just a few. The rich internal structure of atoms and their sensitivity to external fields, both static and time-dependent, provide a unique opportunity to tune interatomic interactions, vary the effective dimensionality of the systems, and shape the external potentials experienced by them.In this talk, I will focus on the role of quantum fluctuations, which can stabilize ultracold systems by preventing their collapse and enabling the formation of self-bound systems known as ultradilute quantum liquid droplets. I will also describe the concept of supersolidity—systems that simultaneously exhibit properties of both superfluids and solids. Finally, novel supersolid systems, particularly those based on mixtures of ultracold bosonic and fermionic species, will be discussed.[1] Quantum Bose-Fermi Droplets, D. Rakshit, T. Karpiuk, M. Brewczyk, M. Gajda, SciPost Phys. 6, 079 (2019),[2] Self-Bound Bose-Fermi Liquids in Lower Dimensions, Debraj Rakshit et al. 2019 New J. Phys. 21 073027,[3] Supersolidity of dipolar Bose-Einstein condensates induced by coupling to fermions, M. Lewkowicz at al., arXiv:2401.05890.

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

Mikołaj Rogóż (IFD UW)

Liquid crystal elastomers: from fabrication to application

Liquid crystal elastomers (LCEs) are elastic polymers capable of reversibly changing shape under external stimuli. The type of deformation they exhibit is determined by the molecular order of the material, which can be achieved through various fabrication methods. These unique properties make LCEs ideal candidates for actuators in mechanics and soft robotics, applicable across different scales and environments. A significant challenge in LCE research remains the development of efficient fabrication techniques, which include methods such as direct laser writing, polymerization in sandwich-like cells, and sequential polymerization.In my talk, I will focus on two key aspects of LCE research: fabrication methods and their applications. First, I will introduce a novel technique for creating self-growing microstructures on optical fiber tips [1]. This approach enables the production of durable, microscale objects with well-oriented materials and offers a cost-effective, straightforward process. I will also discuss polymerization in sandwich-like cells [2], a widely utilized method inspired by techniques established in liquid crystal research over decades.The second part of my talk will explore applications of LCEs in soft robotics and micromechanics. I will present a sunlight-powered, self-oscillating system with potential applications in solar energy harvesting. Experimental results using natural sunlight and its artificial equivalent demonstrated oscillations with frequencies in the single-Hz range. Lastly, I will describe a method for optimizing swimming robots by combining optimization algorithms with experimental feedback. This approach, which employs genetic algorithms and particle swarm optimization, has enabled centimeter-scale underwater swimmers to achieve speeds of up to 10 cm/min.[1] M. Zmyślony, K. Dradrach, J. Haberko, P. Nałęcz‐Jawecki, M. Rogóż, and P. Wasylczyk, ‘Optical Pliers: Micrometer‐Scale, Light‐Driven Tools Grown on Optical Fibers’, Adv. Mater., vol. 32, no. 33, p. 2002779, Aug. 2020, doi: 10.1002/adma.202002779.[2] M. Rogóż, J. Haberko, and P. Wasylczyk, ‘Light-Driven Linear Inchworm Motor Based on Liquid Crystal Elastomer Actuators Fabricated with Rubbing Overwriting’, Materials, vol. 14, no. 21, p. 6688, Nov. 2021, doi: 10.3390/ma14216688.

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

Mateusz Bocheński (IFD UW)

Ultracold mixtures of cesium with potassium isotopes

Studies of fundamental physical phenomena with ultracold atoms, from superfluidity, through quantum simulators, to degenerate gases of polar molecules, require exquisite knowledge of collisional properties of atoms used in experiments. Theoretical predictions are usually based on scarce spectroscopic data and even for molecules like KCs, which have been extensively studied in hot vapors, theoretical understanding of ultracold properties of these molecules is rarely satisfactory. This necessitates the development of efficient cooling methods and extensive experimental studies of fine details of interactions between atoms to provide data for theoretical modeling.In the first part of the talk I will introduce our state-of-the-art experimental setup designed to study ultracold mixtures of cesium and potassium. The versatility of the apparatus will be demonstrated by individually cooling 39K, 40K, 41K, and 133Cs atoms as well as their mixtures. I will compare these findings with state of the art results from other research groups and highlight our achievement of the world’s first 39K-40K and 41K-133Cs mixtures. The second part of the talk will focus on Feshbach resonances spectroscopy of 39K-133Cs and 41K-133Cs mixtures. For 39K-133Cs, we provide the first independent verification of the 2017 results obtained by the group of H.-C. Nägerl (University of Innsbruck). The Feshbach spectrum of 41K-133Cs is demonstrated for the first time, showing significant disagreement with theoretical predictions. These results are vital for a deeper understanding of the collisional properties of cesium and potassium mixtures and are a prerequisite for advancing toward the formation of ultracold polar ground state molecules of KCs.

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

Artur Bednarkiewicz (Institute of Low Temperature and Structure Research, Polish Academy of Sciences)

Photon avalanching in lanthanide doped nanoparticles – the mechanism, applications and challenges

Lanthanide ions doped inorganic nanoparticles (LnNP) are potential candidates and alternative labels to fluorescent molecules and quantum dots. Among the other, they display narrowband absorption and emission lines, multicolour emission, long luminescence lifetimes and are perfectly photostable. In sensitized configuration, they are also capable to efficiently convert NIR excitation to visible range (so called upconversion UC), thus avoiding background fluorescence and enhance signal to background ratio towards super-sensitive biosensing & imaging. They also display non-linearity of luminescence intensity versus pump intensity, which enables imaging beyond diffraction limit with simple, customized confocal setups.Among upconversion processes leading to the anti-Stokes emission, the photon avalanche (PA) became an interesting research topic since 1979, when it was first observed in Pr3+ doped LaCl3 [1]. There are several essential requirements necessary to enable observation of PA in a given system – these include (i) the presence of efficient ESA transition and negligible GSA at the pumping wavelength and (ii) the presence of efficient the cross-relaxation (CR) processes required to populate intermediate excited level. As a consequence, the luminescence intensity of PA increases by several, typically 2-3 orders of magnitude when exciting with power density slightly (e.g. twice) above the PA threshold. Only recently its PA emission was also demonstrated for NaYF4 nanoparticles doped with Tm3+ at the room temperature under 1064 and 1450 nm photoexcitation and 800 nm emission [3].In this lecture, current state-of-the-art on PA emission and the PA emission in nano, micro and bulk LiYF4 crystals will be summarized. Moreover, peculiarities of photon avalanche emission in wider context as the paradigm shift in luminescent nano-bio-labels will be discussed. The wide application potential of PA (e.g. super-resolution imaging [3], biosensing [4], nano-thermometry [5] etc.) makes it extremely interesting to further studies of the PA in various lanthanides and various matrices of various sizes – these applications will be evaluated and future directions & challenges will be emphasized for materialscientists. References: [1] J. S. Chivian, W. E. Case, and D. D. Eden, Appl. Phys. Lett. (1979) 35, 124–125.; [2] M. F. Joubert, Opt. Mater. (Amst). (1999) 11, 181–203.; [3] Ch. Lee et al., Nature (2021), 589, 230-235; A.Bednarkiewicz et al. (2019) Nanoscale Horizons, 4(3), 706-719; [4] A.Bednarkiewicz, E.Chan, K.Prorok, Nanoscale Adv., 2020,2, 4863-4872; [5] M.Szalkowski et

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

Andrei Nomerotski (Florida International University & Czech Technical University)

Time-stamping photons with sub-nanosecond resolution for quantum-enhanced imaging and telescopy

Correlations of photons from entangled quantum sources offer advantages and provide additional opportunities such as low light imaging or new sensing approaches. In general, strong spectro-temporal correlations inherent for entangled photons make those sensing techniques much more precise and resource efficient. To take advantage of the correlations one would need efficient single photon imagers with excellent timing resolution. In the presentation I will review the existing detector options focussing on the time-stamping CMOS and SPAD cameras, which have been used recently in a variety of quantum imaging experiments, in particular the Tpx3Cam and LinoSPAD2 cameras, both based on data-driven readouts. As a motivation for fast imaging in astrophysics I will also review the standard techniques of single-photon amplitude (Michelson) interferometry and two-photon (Hanbury Brown & Twiss) intensity interferometry, and then visit recent ideas for how they can be improved in the optical through the use of entanglement distribution. A proposed new technique of two-photon amplitude interferometry requires precise spectral binning and 10 picosecond scale time-stamping of single optical photons with a product of resolutions close to the Heisenberg Uncertainty Principle limit. Another prominent example of multi-dimensional quantum correlations is the parametric down-conversion of x-rays in diamond. In this case all three types of correlations, in momentum, energy and time, can be measured simultaneously. In all cases I will illustrate the concepts with recent results and will discuss future directions for the technology.[1] A. Nomerotski, “Imaging and time stamping of photons with nanosecond resolution in Timepix based optical cameras,” Nuclear Instruments and Methods A: 937, 26 (2019).[2] Y Zhang, D England, A Nomerotski, B Sussman, "High speed imaging of spectral-temporal correlations in Hong-Ou-Mandel interference," Opt. Express 29, 28217 (2021).[3] P Stankus, A Nomerotski, A Slosar, S Vintskevich, “Two-photon amplitude interferometry for precision astrometry”; Open Journal of Astrophysics 5 (2023).[4] T. Milanese et al. "LinoSPAD2: an FPGA-based, hardware-reconfigurable 512×1 single-photon camera system." Optics Express 31.26 (2023): 44295.[5] J.Jirsa et al. "Fast spectrometer with direct measurement of time and frequency for multiple single photons." arXiv:2304.11999 (2023).[6] J.Goodrich et al, “Imaging of X-ray Pairs in a Spontaneous Parametric Down-Conversion Process,” arXiv:2310.13078 (2023).

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 10:15

Jerzy Szuniewicz (IFD UW)

Phase of a single photon: from measuring to shaping

Single photons play a pivotal role in quantum technologies such as metrology, computing, communications, networking, and quantum key distribution (QKD). They have become essential for transmitting quantum states over long distances, thanks to their weak interactions with matter, compatibility with fiber optics, and technical advances in optical telecommunications. Additionally, photons serve as a cornerstone in both theoretical and experimental research in precise measurements and quantum information processing.In this talk, we will explore the phases carried by single photons, beginning with spatial phases and extending to temporal and spectral phases. We will examine current techniques for dynamically modifying the spectral-temporal modes of single photons and investigate methods for measuring these states. Lastly, we will briefly discuss the role of machine learning in optimizing and shaping single-photon modes.

Stron 2 z 3