Faculty of Physics University of Warsaw > Events > Seminars > Optics Seminar

Optics Seminar

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room 0.06, Pasteura 5 at 10:15

Prof. Maciej Trusiak (Warsaw University of Technology)

Lensless label-free holographic microscopy

Lensless digital holographic microscopy (LDHM), as one of key computational microscopy techniques, performs high-throughput in silico imaging. Numerical propagation of digitally recorded in-line Gabor holograms allows for accessing both amplitude (absorption) and phase (refraction) contrast, devoid of microscope objective limitations, e.g., in depth of field and field of view. The in-line coherent holographic framework induces inherent twin image errors and various coherent artifacts, however. The signal-to-noise ratio of reconstructed holograms additionally deteriorates due to low photon budget environment, favorable in terms of time-lapse photostimulation-free bioimaging of live cells. I plan to discuss several techniques for minimization of LDHM reconstruction errors, and present bio-applications of enhanced LDHM in dynamic (e.g., migrating neural cells) and static (brain tissue slices) scenarios."

room 0.06, Pasteura 5 at 10:15

Prof. Adam Miranowicz (Adam Mickiewicz University, Poznań; RIKEN, Wako, Japan.)

Quantum and semiclassical exceptional points of non-Hermitian systems

I will discuss two topics of non-Hermitian quantum mechanics: No-go theorems in quantum information based on non-Hermitian systems:Recently, apparent nonphysical implications of Bender's non-Hermitian quantum mechanics have been discussed in the literature. In particular, the apparent violation of the no-signaling theorem, discrimination of nonorthogonal states, and the increase of quantum entanglement by local operations were reported, and therefore the Bender theory was not considered to be fundamental. I will show that these and other no-go principles (including the no-cloning and no-deleting theorems) of conventional quantum mechanics still hold in finite-dimensional non-Hermitian quantum systems, including parity-time symmetric and pseudo-Hermitian cases, if its formalism is properly applied. Quantum and semiclassical exceptional points (EPs): When a quantum system is isolated from its environment, it is described by a Hermitian Hamiltonian. Its eigenvalues characterize the resonances frequency, while its eigenvectors describe the form of those resonances. If, however, the system interacts with its environment, some particles will leak, while others will enter. For semiclassical systems, this loss and gain can be captured by a non-Hermitian Hamiltonian, whose eigenvalues represent both the resonance frequencies and lifetime. The presence of the environment can cause two different resonances to become the same, forcing the frequency and the lifetime to match. In this case, we speak of EPs, which are considered as the basis for enhanced sensing measures and are relevant to describe dynamical phase transitions and characterize topological phases of matter. Many exotic phenomena, such as parity-time symmetry breaking and unidirectional propagation, have been observed in the proximity of EPs. The vast majority of the studies on EPs, however, have focused on semiclassical models. To properly describe open quantum systems, quantum jumps, representing the instantaneous switching between the energy levels of the system, must be included. Using Liouvillian quantum jumps, we defined quantum EPs, and showed how, and if, they could correspond to semiclassical EPs. Recent experiments and numerous theoretical studies of various groups confirm the usefulness of the quantum EPs proposed by us. [1] I. I. Arkhipov, A. Miranowicz, F. Minganti, K. Özdemir, F. Nori, Nat. Comm. 14, 2076 (2023). [2] D.-G. Lai, C.-H. Wang, A. Miranowicz, and F. Nori, Optica 11, 485 (2024).[3] C.-Y. Ju, A. Miranowicz, Y.-N. Chen, G.-Y. Chen, F. Nori, Quantum 8, 1277 (2024). [4] A. Laha, A. Miranowicz, R. K. Varshney, and S. Ghosh, Phys. Rev. A 109, 033511 (2024). [5] I. I. Arkhipov, A. Miranowicz, F. Nori, S. K. Özdemir, F. Minganti, Phys. Rev. Res. 108, 033512 (2023). [6] J. Perina Jr., A. Miranowicz, J. K. Kalaga, W. Leonski, Phys. Rev. A 108, 033512 (2023). [7] C.-Y. Ju, A. Miranowicz, F. Minganti, C.-Ts. Chan, G.-Y. Chen, F. Nori, Phys. Rev. Res. 4, 023070 (2022). [8] C.-Y. Ju, A. Miranowicz, G.-Y. Chen, F. Nori, Phys. Rev. A 100, 062118 (2019). [9] F. Minganti, A. Miranowicz, R. Chhajlany, F. Nori, Phys. Rev. A 100, 062131 (2019). [10] S. Abo, P. Tulewicz, K. Bartkiewicz, S. K. Özdemir, and A. Miranowicz, e-print arXiv:2401.14993 (2024). [11] D.-G. Lai, A. Miranowicz, F. Nori, to appear in Phys. Rev. Lett. (2024).

room 0.06, Pasteura 5 at 10:15

dr inż. Grzegorz Kowzan (UMK Toruń)

Towards cavity-enhanced two-dimensional ifrared spectroscopy of gas-phase molecules

2DIR spectroscopy is a powerful and well-developed experimental technique, commonly used to study ultrafast molecular dynamics in optically thick liquid-phase and solid-state samples [1].Advances in generation of high-power optical frequency combs in the mid infrared and in cavity enhancement of ultrafast nonlinear signals provide a way to extend 2DIR measurements to weakly absorbing samples, in particular to low-concentration gas-phase samples [2].The high sensitivity of these techniques can be combined with the high resolution of multicomb spectroscopy or Fourier-transform spectroscopy to enable measurements of the shapes of individual resonances.In this talk, I will explain the principles of (cavity-enhanced) two-dimensional infrared spectroscopy with frequency combs and discuss our plan for experimental realization of this technique, including our plans to study optical coherence transport in room-temperature gas-phase molecules [3] and intra-/intermolecular vibrational dynamics in cold molecules.[1] P. Hamm and M. Zanni, Concepts and Methods of 2D Infrared Spectroscopy, 1st ed. (Cambridge University Press, Cambridge, 2011).[2] M. C. Silfies, A. Mehmood, G. Kowzan, E. G. Hohenstein, B. G. Levine, and T. K. Allison, J. Chem. Phys 159, 104304 (2023).[3] G. Kowzan, H. Cybulski, P. Wcisło, M. Słowiński, A. Viel, P. Masłowski, and F. Thibault, Phys. Rev. A 102, 012821 (2020)."

room 0.06, Pasteura 5 at 10:15

prof. Krzysztof Sacha (Uniwersytet Jagielloński)

Time-tronics: from temporal printed circuit board to quantum computer

Time crystalline structures can be created in periodically driven systems. They are temporal lattices which can reveal different condensed matter behaviours ranging from Anderson localization in time to temporal analogues of many-body localization or topological insulators. However, the potential practical applications of time crystalline structures have not yet been demonstrated. We pave the way for time-tronics where temporal lattices are like printed circuit boards for realization of a broad range of quantum devices. The elements of these devices can correspond to structures of dimensions higher than three and can be arbitrarily connected and reconfigured at any moment. Moreover, our approach allows for the construction of a quantum computer, enabling quantum gate operations for all possible pairs of qubits. Our findings indicate that the limitations faced in building devices using conventional spatial crystals can be overcome by adopting crystalline structures in time.

room 0.06, Pasteura 5 at 10:15

Dr Mattia Longobucco (Łukasiewicz — Institute of Microelectronics and Photonics.)

Solitonic steering of femtosecond pulses in coupled waveguides: exploring two all-optical switching schemes using soft-glass asymmetric dual-core fibers

The research explores pulse energy-controlled solitonic steering of femtosecond pulses in highly nonlinear dual-core fibers, offering insights into ultrafast nonlinear fiber optics and soliton theory in coupled waveguides. Specially designed dual-core fibers facilitate energy-driven switching of femtosecond pulses, leveraging the nonlinear self-trapping of high-order solitons induced by the Kerr effect. Numerical optimization of fiber structure and experimental validation demonstrate optimal switching parameters, spectral uniformity, and the impact of dual-core asymmetry. Notably, two innovative schemes are presented: 1) Self-switching: Demonstrating reversible switching with sub-nJ pulses, exhibiting soliton-like behavior, and showcasing broadband performance. 2) Dual wavelength approach: Introducing a method based on the interaction between synchronized femtosecond pulses at different wavelengths, enabling efficient switching with high contrasts and minimal wavelength shifts.. The study underscores the potential for practical applications in compact, low-power, all-optical switching devices for optical communications.

room 0.06, Pasteura 5 at 10:15

prof. Krzysztof Pawłowski (IFT UW)

Quasi-1D quantum dipolar droplets

In 2016, the Tilman Pfau's group from Stuttgart measured an unexpected phenomenon, the formation of quantum droplets out of ultracold gas. This happened in the regime of interaction when matter should explode as a supernova. It has been shown that the unexpected stability is due to quantum correlations and three-body effects, that determine the macroscopic properties of this new phase.Our theoretical research focuses on studying quasi-one-dimensional system. The interplay between the attractive dipolar and repulsive van der Waals interactions may lead also to quantum self-bound states, as pointed out in [1]. First we’ve showed that the droplet form for any interaction regime,including fermionied system [2], and then we pointed out novel many-body effects and nonlinear phenomena. Within a dipolar quantum droplet, one may generate a dark solitary wave with a steerable width, theoretically infinitely broad [3]. Intriguingly, a one-dimensional dipolar droplet, when subjected to a change in van der Waals interaction strength from repulsive to attractive, exhibits unexpected many-body behaviour. Instead of collapsing (which, intuitively, would be the expected scenario given all forces are attractive) or increasing stability (as known due to the super Tonks-Girardeau effect), the droplet evaporates [4]. I would like to elucidate the origin of such droplets and their unexpected features.[1] D. Edler, C. Mishra, F. Wachtler, R. Nath, S. Sinha, L. Santos, Phys. Rev. Lett. 119, 050403 (2017)[2] R. Ołdziejewski, W. Gorecki, K. Pawłowski, K. Rzazewski, Phys. Rev. Lett. 124, 090401 (2020)[3] J. Kopycinski, M. Łebek, W. Górecki, K. Pawłowski, Phys. Rev. Lett. 130, 043401 (2023)[4] M. Marciniak, M. Łebek, J. Kopycinski, W. Górecki, R. Ołdziejewski, K. Pawłowski, Phys. Rev. A 108, 043304 (2023)"

room 0.06, Pasteura 5 at 10:15

prof. Barbara Piętka (IFD UW)

Chiral and edge-lasing with perovskite crystals of arbitrary shape

The search for material platforms that ensure low cost, ease of fabrication, usability (room temperature) and nonlinearity in the same device is a serious challenge for today's photonics. Our work presents a first step towards a major breakthrough in the field of perovskite integrated photonics. For this purpose, we developed a versatile, template-assisted method for fabricating perovskite microstructures of any arbitrary, pre-defined shape. Our structures demonstrate waveguiding capabilities and facilitate the formation of spatially extended condensates of coherent exciton-polaritons. Our microwires, characterized by their ability to bend without compromising optical quality, are formed from CsPbBr3 crystals and can be deposited on any substrate, enhancing compatibility with existing photonic devices. Notably, our method overcomes the limitations of traditional waveguiding setups by eliminating the need for extrinsic cavity mirrors. Our approach significantly simplifies the fabrication process, making on-chip polaritonic devices more accessible and cost-effective.We demonstrate polariton lasing from the interfaces and corners of the microwires, with large blueshifts observed with excitation power. The high mutual coherence between different edge and corner lasing signals, evidenced in the far-field photoluminescence and angle-resolved spectroscopy, indicates the formation of a coherent, extended over macroscopic distance polariton condensate. This condensate is capable of propagating over long distances within the wires and even coupling between neighbouring wires through air-gaps. Perovskite crystals can also be enclosed in photonic microcavity composed of two Bragg mirrors and, additionally,the cavity can be filled with a highly birefringent liquid crystal. The birefringence is controlled by external electric field which allows to drive the system through wide range of H-V split photonic modes and spin-orbit coupled modes of Rashba-Dresselhaus type. The strong light-matter coupling condition is achieved with subsequent cavity modes, what allow us to observe non-linear effect at low threshold powers. The polariton lasing at room temperature is revealed in all regimes, including chiral lasing from circularly polarized polariton bands. The simplicity and scalability of our platform, combined with its compatibility with standard photonic components,pave the way for future large-scale, integrated polaritonic circuitry. Our findings not only demonstrate the potential of CsPbBr3 perovskites in photonic applications but also provide a more accessible path for the development of advanced on-chip optical devices with built-in nonlinearities.

room 0.06, Pasteura 5 at 10:15

Prof. Maciej Trusiak (Politechnika Warszawska)

odwołane / cancelled: Lensless label-free holographic microscopy

room 0.06, Pasteura 5 at 10:15

dr Michał Karpiński (IFD UW)

Phase-only shaping of optical pulses

room 0.06, Pasteura 5 at 10:15

prof. Nicolas Treps (Sorbonne University)

Parameter estimation with light, from the quantum Cramér-Rao bound to the experimental estimation of incoherent sources separation

Resolution in imaging is bounded by measurement design, detectors sensitivity, light source noise and, ultimately, the quantum nature of light. Quantum metrology provides the framework to compute the ultimate precision limit on the estimation of any parameter encoded in a beam of light. In particular, the Cramér-Rao bound indicates the minimum variance of any unbiased estimator for a given measurement setting, and its quantum counterpart its optimisation over all measurements allowed by quantum mechanics. This limit is used has a benchmark to evaluate the performances of actual measurements. As a consequence, before considering any purely quantum effects, one has to ascertain saturation of the QCRB with classical sources. This is a key point that should become a strategy when optimising or proposing new imaging systems.After introducing these general concepts and their implication to optical parameter estimation, we will take the example of the quantum-metrology-inspired approach for estimating the separation between two incoherent sources. We will show experimentally how spatial mode decomposition allows for ultra-sensitive estimation.

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