ORCID Profile
0000-0002-4767-5705
Current Organisation
Australian National University
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: Wiley
Date: 24-02-2015
DOI: 10.1002/JOC.4268
Publisher: OSA
Date: 2019
Publisher: Springer Science and Business Media LLC
Date: 27-04-2018
DOI: 10.1038/S41598-018-25018-2
Abstract: Owing to their integer spin, exciton-polaritons in microcavities can be used for observation of non-equilibrium Bose-Einstein condensation in solid state. However, spin-related phenomena of such condensates are difficult to explore due to the relatively small Zeeman effect of standard semiconductor microcavity systems and the strong tendency to sustain an equal population of two spin components, which precludes the observation of condensates with a well defined spin projection along the axis of the system. The enhancement of the Zeeman splitting can be achieved by introducing magnetic ions to the quantum wells, and consequently forming semimagnetic polaritons. In this system, increasing magnetic field can induce polariton condensation at constant excitation power. Here we evidence the spin polarization of a semimagnetic polaritons condensate exhibiting a circularly polarized emission over 95% even in a moderate magnetic field of about 3 T. Furthermore, we show that unlike nonmagnetic polaritons, an increase on excitation power results in an increase of the semimagnetic polaritons condensate spin polarization. These properties open new possibilities for testing theoretically predicted phenomena of spin polarized condensate.
Publisher: American Physical Society (APS)
Date: 16-08-2017
Publisher: American Society of Mechanical Engineers
Date: 19-06-2016
Abstract: During the past decades, a large number of waves of extreme height and abnormal shape, also known as freak or rogue waves, have been recorded in the ocean. Velocities and related forces can be enormous and jeopardise the safety of marine structures. Here, we present an experimental study devoted to investigate the velocity field underneath a breaking rogue wave. The latter is replicated in the laboratory by means of dispersive focussing methods such as the New Wave Theory and nonlinear focussing techniques based on the Nonlinear Schrödinger equation. While the former is basically a liner method, the nonlinear focussing fully accounts for the dynamical evolution of the wave field. Experiments were carried out in the Extreme Air-Sea Interaction flume of the University of Melbourne using a Particle Image Velocimetry (PIV) system to measure the velocity field below the water surface. Measurements show that the mechanism of generation affects the shape of the breaking waves as well as the kinematic field and associated hydrodynamic forces. Particularly, the New Wave Theory leads to higher velocities and a more energetic breaker than the nonlinear focussing.
Publisher: American Physical Society (APS)
Date: 26-04-2018
Publisher: American Geophysical Union (AGU)
Date: 02-2016
DOI: 10.1002/2015JC011225
Publisher: Elsevier BV
Date: 2020
Publisher: American Physical Society (APS)
Date: 28-01-2022
Publisher: American Physical Society (APS)
Date: 25-08-2021
Publisher: American Meteorological Society
Date: 21-10-2016
Abstract: Twenty years (1996–2015) of satellite observations were used to study the climatology and trends of oceanic winds and waves in the Arctic Ocean in the summer season (August–September). The Atlantic-side seas, exposed to the open ocean, host more energetic waves than those on the Pacific side. Trend analysis shows a clear spatial (regional) and temporal (interannual) variability in wave height and wind speed. Waves in the Chukchi Sea, Beaufort Sea (near the northern Alaska), and Laptev Sea have been increasing at a rate of 0.1–0.3 m decade−1, found to be statistically significant at the 90% level. The trend of waves in the Greenland and Barents Seas, on the contrary, is weak and not statistically significant. In the Barents and Kara Seas, winds and waves initially increased between 1996 and 2006 and later decreased. Large-scale atmospheric circulations such as the Arctic Oscillation and Arctic dipole anomaly have a clear impact on the variation of winds and waves in the Atlantic sector. Comparison between altimeter observations and ERA-Interim shows that the reanalysis winds are on average 1.6 m s−1 lower in the Arctic Ocean, which translates to a low bias of significant wave height (−0.27 m) in the reanalysis wave data.
Publisher: American Physical Society (APS)
Date: 11-2021
Publisher: American Geophysical Union (AGU)
Date: 04-2017
DOI: 10.1002/2016MS000878
Publisher: IOP Publishing
Date: 22-10-2019
Publisher: American Chemical Society (ACS)
Date: 26-02-2021
Publisher: Wiley
Date: 30-09-2022
Abstract: This paper introduces a new approach to neuromorphic photonics in which microcavities exhibiting strong exciton–photon interaction may serve as building blocks of optical spiking neurons. The experimental results demonstrate the intrinsic property of exciton–polaritons to resemble the Leaky Integrate‐and‐Fire (LIF) spiking mechanism. It is shown that exciton–polariton microcavities when non‐resonantly pumped with a pulsed laser exhibit leaky integration due to relaxation of the excitonic reservoir, threshold‐and‐fire mechanism due to transition to Bose–Einstein Condensate (BEC), and resetting due to stimulated emission of photons. These effects, evidenced in photoluminescence characteristics, arise within sub‐ns timescales. The presented approach provides means for ultrafast processing of spike‐like laser pulses with energy efficiency at the level below 1 pJ per spike.
Publisher: Optica Publishing Group
Date: 29-08-2023
DOI: 10.1364/OME.492285
Abstract: An optical resonator is utilized to enhance interactions between photons and solid-state emitters. In particular, when the coupling strength between the exciton within the material is faster than the dissipation rate, the eigenstates of the system are mixed light-matter quasiparticles referred to as exciton-polaritons. In this work, we demonstrate an open, planar cavity platform for investigating a strong coupling regime. The open cavity approach supports ease of integration of erse material systems and in situ tunability of the photonic resonance. We characterize the strong coupling regime in systems ranging from thin 2D semiconductors, perovskites, and II-VI semiconductor quantum wells.
Publisher: Elsevier BV
Date: 07-2016
Publisher: American Association for the Advancement of Science (AAAS)
Date: 08-11-2019
Abstract: The coupling of the spin-orbit interactions in solid-state systems can give rise to a wide range of exotic electronic transport effects. But solid-state systems tend to be somewhat limited in their flexibility because the spin-orbit coupling is fixed. By contrast, optical systems have recently been shown to mimic complex solid-state systems, with flexibility in design providing the ability to control and manipulate the system properties. Using a liquid crystal–filled photonic cavity, Rechcińska et al. emulated an artificial Rashba-Dresselhaus spin-orbit coupling in a photonic system and showed control of an artificial Zeeman splitting. The results illustrate a powerful approach of engineering synthetic Hamiltonians with photons for the simulation of nontrivial condensed matter and quantum phenomena. Science , this issue p. 727
Publisher: American Physical Society (APS)
Date: 21-02-2017
Publisher: AIP Publishing
Date: 16-11-2015
DOI: 10.1063/1.4935791
Abstract: We report on properties of an optical microcavity based on (Cd,Zn,Mg)Te layers and embedding (Cd,Zn)Te quantum wells. The key point of the structure design is the lattice matching of the whole structure to MgTe, which eliminates the internal strain and allows one to embed an arbitrary number of unstrained quantum wells in the microcavity. We evidence the strong light-matter coupling regime already for the structure containing a single quantum well. Embedding four unstrained quantum wells results in further enhancement of the exciton-photon coupling and the polariton lasing in the strong coupling regime.
Publisher: ACM
Date: 19-04-2023
Publisher: Optica Publishing Group
Date: 14-08-2023
Abstract: In this work, we observe natural exceptional points in the excitation spectrum of an exciton–polariton system by optically tuning the light–matter interactions. The observed exceptional points do not require any spatial or polarization degrees of freedom and result solely from the transition from weak to strong light–matter coupling. It was demonstrated that they do not coincide with the threshold for photon lasing, confirming previous theoretical predictions [ Phys. Rev. Lett. 122 , 185301 ( 2019 ) PRLTAO 0031-9007 10.1103/PhysRevLett.122.185301 , Optica 7 , 1015 ( 2020 ) OPTIC8 2334-2536 10.1364/OPTICA.397378 ]. Using a technique where a strong coherent laser pump induces up-converted excitations, we encircle the exceptional point in the parameter space of coupling strength and particle momentum. Our method of local optical control of light–matter coupling paves the way to the investigation of fundamental phenomena, including dissipative phase transitions and non-Hermitian topological states.
Publisher: American Physical Society (APS)
Date: 22-05-2022
Publisher: American Physical Society (APS)
Date: 28-03-2019
Publisher: Elsevier BV
Date: 04-2016
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9NR02038A
Abstract: Strong light–matter interaction between cavity photons and excitons in monolayer WSe 2 with spin selective excitation is demonstrated.
Publisher: American Physical Society (APS)
Date: 05-09-2017
Publisher: American Meteorological Society
Date: 05-2016
DOI: 10.1175/JTECH-D-15-0219.1
Abstract: Hai Yang-2 ( HY-2 ) satellite altimeter measurements of significant wave height ( ) are analyzed over the period from 1 October 2011 to 6 December 2014. They are calibrated and validated against in situ buoys and other concurrently operating altimeters: Jason-2 , CryoSat-2 , and Satellite with Argos and ALtiKa ( SARAL ). In general, the HY-2 altimeter measurements agree well with buoy measurements, with a bias of −0.22 m and a root-mean-square error (RMSE) of 0.30 m. When the reduced major axis (RMA) regression procedure was applied to the entire period, the RMSE was reduced by 33% to 0.2 m. A further comparison with other satellite altimeters, however, revealed two additional features of HY-2 estimates over this period. First, a noticeable mismatch is present between HY-2 and the other satellite altimeters for high seas ( 6 m). Second, a jump increase in HY-2 values was detected starting in April 2013, which was associated with the switch to backup status of the HY-2 sensors and the subsequent update of its data processing software. Although reported by previous studies, these two deficiencies had not been accounted for in calibrations. Therefore, the HY-2 wave height records are now sub ided into two phases (time periods pre- and post-April 2013) and a two-branched calibration is proposed for each phase. These revised calibrations, validated throughout the range of significant wave heights of 1–9 m, are expected to improve the practical applicability of HY-2 measurements significantly.
Publisher: Optica Publishing Group
Date: 16-02-2021
Abstract: Multicomponent Bose–Einstein condensates, quantum Hall systems, and chiral magnetic materials display twists and knots in the continuous symmetries of their order parameters known as skyrmions. Originally discovered as solutions to the nonlinear sigma model in quantum field theory, these vectorial excitations are quantified by a topological winding number dictating their interactions and global properties of the host system. Here, we report the experimental observation of a stable in idual second-order meron and antimeron appearing in an electromagnetic field. We realize these complex textures by confining light into a liquid-crystal-filled cavity that, through its anisotropic refractive index, provides an adjustable artificial photonic gauge field that couples the cavity photon motion to its polarization, resulting in the formation of these fundamental vectorial vortex states of light. Our observations could help bring topologically robust room-temperature optical vector textures into the field of photonic information processing and storage.
Publisher: American Meteorological Society
Date: 09-2016
Abstract: Laboratory experiments were performed to investigate the effects of a coflowing current field on the spectral shape of water waves. The results indicate that refraction is the main factor in modulating wave height and overall wave energy. Although the structure of the current field varies considerably, some current-induced patterns in the wave spectrum are observed. In high frequencies, the energy cascading generated by nonlinear interactions is suppressed, and the development of a spectral tail is disturbed, as a consequence of the detuning of the four-wave resonance conditions. Furthermore, the presence of currents slows the downshifting of the spectral peak. The suppression of the high-frequency energy under the influence of currents is more prominent as the spectral steepness increases. The energy suppression is also more accentuated and long-standing along the fetch when the directional spreading of waves is sufficiently broad. This result indicates that the current-induced detuning of resonant conditions is more effective when exact resonances are the primary mechanism of nonlinear interactions than when quasi resonances prevail (directionally narrow cases). Additionally, the directional analysis shows that the highly variable currents broaden the directional spreading of waves. The broadening is suggested to be related to random refraction and scattering of wave rays. The random disturbance of wavenumbers alters the nonlinear interaction conditions and weakens the energy exchanges among wave components, which is expressed in the suppression of the high-frequency energy.
Publisher: AIP Publishing
Date: 04-2023
DOI: 10.1063/5.0136380
Abstract: Exciton–polaritons in optical cavities exhibit strong nonlinearities predominantly because of the third-order Kerr-like interactions mediated by the excitonic component. Under quasi-resonant excitation, depending on the energy of the incident laser, it results in the optical limiting or bistable behavior. The latter phenomenon is manifested by the hysteresis loop observed in the input–output power characteristics, when a cavity is quasi-resonantly driven by a laser field. The direction of the loop is typically counterclockwise when increasing and subsequently decreasing the optical power. In this work, we demonstrate the optical bistability with an inverted hysteresis direction. It is observed in an exfoliated CdTe-based semiconductor microcavity when the frequency of the pumping laser is tuned slightly below the lower polariton mode. This unusual behavior is caused by the interplay of the suppression of strong coupling and the redshift of the lower polariton mode energy when increasing the incident power. We show that under these conditions, the polariton microcavity can be used as an optical limiter. All of the experimental observations, the shape and the direction of the hysteresis and the optical limiting behavior, are fully supported by a theoretical model.
Publisher: American Geophysical Union (AGU)
Date: 04-2017
DOI: 10.1002/2016MS000707
Publisher: American Physical Society (APS)
Date: 04-08-2017
Publisher: Springer Science and Business Media LLC
Date: 09-2015
Publisher: Springer Science and Business Media LLC
Date: 12-09-2022
DOI: 10.1038/S41467-022-33001-9
Abstract: Topological physics relies on Hamiltonian’s eigenstate singularities carrying topological charges, such as Dirac points, and – in non-Hermitian systems – exceptional points (EPs), lines or surfaces. So far, the reported non-Hermitian topological transitions were related to the creation of a pair of EPs connected by a Fermi arc out of a single Dirac point by increasing non-Hermiticity. Such EPs can annihilate by reducing non-Hermiticity. Here, we demonstrate experimentally that an increase of non-Hermiticity can lead to the annihilation of EPs issued from different Dirac points (valleys). The studied platform is a liquid crystal microcavity with voltage-controlled birefringence and TE-TM photonic spin-orbit-coupling. Non-Hermiticity is provided by polarization-dependent losses. By increasing the non-Hermiticity degree, we control the position of the EPs. After the intervalley annihilation, the system becomes free of any band singularity. Our results open the field of non-Hermitian valley-physics and illustrate connections between Hermitian topology and non-Hermitian phase transitions.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 07-10-2022
Abstract: The field of spinoptronics is underpinned by good control over photonic spin-orbit coupling in devices that have strong optical nonlinearities. Such devices might hold the key to a new era of optoelectronics where momentum and polarization degrees of freedom of light are interwoven and interfaced with electronics. However, manipulating photons through electrical means is a daunting task given their charge neutrality. In this work, we present electrically tunable microcavity exciton-polariton resonances in a Rashba-Dresselhaus spin-orbit coupling field. We show that different spin-orbit coupling fields and the reduced cavity symmetry lead to tunable formation of the Berry curvature, the hallmark of quantum geometrical effects. For this, we have implemented an architecture of a photonic structure with a two-dimensional perovskite layer incorporated into a microcavity filled with nematic liquid crystal. Our work interfaces spinoptronic devices with electronics by combining electrical control over both the strong light-matter coupling conditions and artificial gauge fields.
Publisher: Elsevier BV
Date: 12-2015
Publisher: American Physical Society (APS)
Date: 10-03-2023
Publisher: Institute of Physics, Polish Academy of Sciences
Date: 08-2017
Publisher: Springer Science and Business Media LLC
Date: 10-10-2018
DOI: 10.1038/S41377-018-0076-Z
Abstract: The spin Hall effect, a key enabler in the field of spintronics, underlies the capability to control spin currents over macroscopic distances. The effect was initially predicted by D'Yakonov and Perel 1 and has been recently brought to the foreground by its realization in paramagnetic metals by Hirsch 2 and in semiconductors 3 by Sih et al. Whereas the rapid dephasing of electrons poses severe limitations to the manipulation of macroscopic spin currents, the concept of replacing fermionic charges with neutral bosons such as photons in stratified media has brought some tangible advances in terms of comparatively lossless propagation and ease of detection 4–7 . These advances have led to several manifestations of the spin Hall effect with light, ranging from semiconductor microcavities 8,9 to metasurfaces 10 . To date the observations have been limited to built-in effective magnetic fields that underpin the formation of spatial spin currents. Here we demonstrate external control of spin currents by modulating the splitting between transverse electric and magnetic fields in liquid crystals integrated in microcavities.
Publisher: American Physical Society (APS)
Date: 18-02-2015
Publisher: Springer Science and Business Media LLC
Date: 08-2023
DOI: 10.1038/S42005-023-01319-5
Abstract: The insensitivity of photons towards external magnetic fields forms one of the hardest barriers against efficient magneto-optical control, aiming at modulating the polarization state of light. However, there is even scarcer evidence of magneto-optical effects that can spatially modulate light. Here, we demonstrate the latter by exploiting strongly coupled states of semimagnetic matter and light in planar semiconductor microcavities. We nonresonantly excite two spatially adjacent exciton-polariton condensates which, through inherent ballistic near field coupling mechanism, spontaneously synchronise into a dissipative quantum fluidic supermode of definite parity. Applying a magnetic field along the optical axis, we continuously adjust the light-matter composition of the condensate exciton-polaritons, inducing a supermode switch into a higher order mode of opposite parity. Our findings set the ground towards magnetic spatial modulation of nonlinear light.
No related grants have been discovered for Mateusz Król.