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Seminarium Optyczne

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

Roman Ciuryło (Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Toruń)

Optical metrology of atomic and molecular systems

The energetic structure of atoms and molecules is determined by the interaction between their components and the surrounding space. Therefore atoms can be used to look for perturbation by dark matter fields. On the other hand, molecules are especially attractive to test quantum electrodynamics (QED) in systems more complex than a single atom and look for more exotic interactions like hadron-hadron fifth forces or short range non-Newtonian gravitation. It was demonstrated that even a single optical atomic clock can be sensitive to coupling with a possible dark matter field and the global network of such sensors was arranged. Doppler limited cavity-ring down spectra of D2 analysed with ab initio line shape profiles provided an accurate experimental test of QED calculations for this system. A proof-of-principle demonstration of use of photoassociation spectroscopy of weakly bound molecules was carried with ultracold Yb2 for determination of constraints on fifth forces or non-Newtonian interactions between atoms. Prospects for farther improvement of discussed techniques can be seen in a pure frequency dispersion spectroscopy, development of optical molecular clocks and use of ultracold systems involving Hg atoms. Moreover, new areas of investigations are opened by laser cooling of positronium.

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

Maciej Wojtkowski (International Center for Translational Eye Research - ICTER and Institute of Physical Chemistry, Polish Academy of Sciences)

Spatio-temporal optical coherence tomography – new method for in vivo structural and functional imaging

Achieving in vivo optical microscopy with quality comparable to fixed samplescontinues to be challenging. We developed Spatio-Temporal Optical Coherence (STOC)Imaging, which dynamically randomizes the spatial phase relationships of the illuminatinglight to enhance image quality. When extended to three-dimensional imaging as Spatio-Temporal Optical Coherence Tomography (STOC-T), the method employs hundreds ofuncorrelated spectral interferograms to amplify ballistic photon signals while suppressingscattered photon contributions. STOC-T delivers rapid, high-contrast imaging and maintainshigh resolution at significant depths without the need for repeated measurements. In ocularimaging applications, STOC-T supports functional imaging methods such asOptoretinography (ORG), which measures photoreceptor responses to light stimuli. Weintroduced Flicker Optoretinography (f-ORG) for tracking rapid optical path-length changesunder photopic conditions, achieving reproducible sensitivity on the order of a singlenanometer in light-adapted eyes. This approach advances our understanding of retinalresponses and photopigment photo-activation processes.

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

Jacek Szczepkowski (Institute of Physics, Polish Academy of Sciences)

Electronic structure of diatomic molecules. New challenges

Ultracold molecules provide an ideal platform for exploring the fundamental aspects of quantum physics and chemistry. Diatomic molecules with permanent electric dipole moments have already been employed to achieve the first ultracold, controlled chemical reactions, perform precision measurements, and enable quantum simulations of many-body dynamics. Moreover, the prospects for their application in quantum computing have recently driven the development of single-molecule control using optical tweezers. The rapid progress in this field has motivated an increasing number of research groups worldwide to begin investigating polar molecules at ultralow temperatures. A detailed understanding of the molecular electronic structure is essential for the development of such experiments. This presentation will focus on the new challenges in the spectroscopic investigation of the electronic structure of selected diatomic molecules.

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

Joanna Olesiak-Bańska (Politechnika Wrocławska)

Probing chiral one- and two-photon properties in noble metal nanoclusters

Noble metal nanoclusters (NCs) are ultra-small nanomaterials exhibiting optical properties intermediate to those of discrete molecules and bigger nanoparticles [1]. They possess exceptional linear and nonlinear optical characteristics, including tunable photoluminescence (UV-NIR), large Stokes shifts (>0.5 eV), high photostability, and significant two-photon absorption [2]. Importantly, many NCs display chirality, arising from chiral surface ligands, helical core motifs, or inherent kernel asymmetry [3]. These attributes make NCs excellent models for structure-property relationship studies and versatile tools in catalysis, bioimaging, and sensing.This work investigates the linear and nonlinear optical properties of NCs with diverse chirality origins. We synthesized and characterized NCs stabilized by: 1) chiral ligands within primary or secondary ligand shells (captopril, glutathione, arginin, single stranded DNA), and 2) achiral ligands where chirality was induced by the arrangement of staple motifs. To quantitatively assess chiral nonlinear optical properties, specifically two-photon circular dichroism (2PCD), we developed and employed two distinct methodologies: z-scan-based two-photon absorption measurements and fluorescence-detected two-photon excited luminescence measurements utilizing circularly polarized light [4, 5]. Our findings reveal that the 2PCD of these NCs is approximately 300 times stronger than their one-photon anisotropy factor. Furthermore, we successfully demonstrated the facile detection of both 2PCD and three-photon circular dichroism (3PCD) in chiral gold NCs [6]. This research provides critical insights into the interplay between chirality and nonlinear optical phenomena in NCs, opening new avenues for their application in advanced photonics and chiroptical technologies.References[1] I. Chakraborty et al., Chem. Rev. 2017, 117, 8208.[2] J. Olesiak-Banska et al., Chem. Soc. Rev. 2019, 48, 4087.[3] I. Dolamic, S. Knoppe, A. Dass et al. Nat. Commun. 2012, 3, 798.[4] J. Olesiak-Banska et al., RSC Adv., 2016, 6. 98748.[5] A. Pniakowska et al. Nanoscale 2023; 15, 8597-8602.[6] P. Obstarczyk et al. J. Am. Chem. Soc. 2024, 146, 51, 35011–35015.

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

Tomasz Karpiuk (Uniwersytet w Białymstoku)

Three-dimensional Bose-Fermi droplets at nonzero temperatures

We numerically study the formation of self-bound quantum Bose-Fermi droplets at nonzero temperatures. We have previously shown that such droplets can exist at zero temperature. In this work the attractive atomic Bose-Fermi mixture is described in terms of quantum hydrodynamics, enriched by beyond mean-field corrections and thermal fluctuations, as well as by a simplified self-consistent Hartree-Fock model. Using the hydrodynamic description, we find low-temperature relatively long-lived droplets in a free space, provided that the attraction between bosons and fermions is strong enough. On the other hand, a simplified Hartree-Fock treatment supports the existence of Bose-Fermi droplets in equilibrium with the gas of thermal bosons and fermions, with the Bose-Einstein condensate itself being completely hidden inside a droplet. Both thermal and non-thermal droplets can be used to simulate astrophysical phenomena such as disruption of a white dwarf star by a black hole.

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

Konstantin Bliokh (Donostia International Physics Center, Spain)

Momentum and angular momentum of classical waves

In addition to their oscillatory behavior, waves possess dynamical properties, such as energy, momentum, and angular momentum. The momentum of waves is associated with their propagation direction, i.e. the phase gradient. The circulation of the wave momentum density gives rise to orbital angular momentum (AM). Additionally, for waves described by vector fields, local rotation of the wavefield produces spin AM (or simply, spin). These dynamical wave properties become particularly significant in structured (i.e. inhomogeneous) wavefields. I will provide an introduction and overview of the momentum and AM properties for various classical waves: electromagnetic, sound, and water-surface waves. A unified field-theory approach, based on Noether’s theorem, offers a general framework to describe these diverse physical systems, encompassing longitudinal, transverse, and mixed waves with different dispersion characteristics. I will also discuss observable manifestations of the wave momentum and AM in terms of radiation forces and torques on small particles, which provide clear physical interpretations of the derived quantities.