arXiv subjects

Sylwia Zielińska-Raczyńska

Publications and source records attributed to Sylwia Zielińska-Raczyńska.

At least 19 recordsLinked to original sources

arXiv2026

Rydberg excitons in core-shell nanostructures II. Plasmon-exciton interaction and enhancement

Interaction between Rydberg excitons in core-shell Cu$_2$O nanostructures and surface plasmons is investigated. An enhancement of a quadrupole transitions to the Rydberg exciton states in copper oxide plasmonic nanaostructures is examined. A possibility of a modification of plasmonic enhancment (i.e., an average amplification factor) of electric field distributions in the vicinity of nanostructures, which depends on its shape and geometrical size, is also discussed.

cond-mat.mes-hall↗

arXiv2026

Rydberg excitons in core-shell nanostructures I. Optical properties

Optical properties of Cu$_2$O-metal core-shell nanostructures containing Rydberg excitons are examined. Calculations of electron and hole eigenfunctions and eigenenergies are used to calculate exciton energy and its dependence on system geometry and dimensionality. The limits of very small and very large structures are discussed, making the results applicable to low principal quantum number excitons as well as to Rydberg states. The Real Density Matrix Approach method is used to calculate the optical properties of the studied systems.

cond-mat.mes-hall↗

arXiv2026

Propagation processing of short pulses in Rydberg exciton medium under blockade conditions

Propagation of short pulses through Cu$_2$O crystal containing Rydberg excitons is studied with the use of density matrix formalism and FDTD method. Saturation effects related to the so-called Rydberg blockade are studied extensively, exploring not only reduction of absorption (bleaching) but also power-dependent changes of the dispersive properties of the medium. The role of exciton lifetime and coherent population oscillations in the dynamics of the system is investigated. A pump-probe setup with two pulses is also studied, showing good agreement with recent experimental studies.

cond-mat.mes-hall↗

arXiv2025

Plasmon-enhanced quadrupole transitions of Rydberg excitons in Cu2O

A mechanism for amplification of weak quadrupole transitions of Rydberg excitons in Cu$_2$O by a plasmonic nanostructure is investigated. The theoretical description of exciton-plasmon interaction is presented and a field averaging approximation is proposed for calculations involving large excitons. Various types of copper, silver and gold-based plasmonic nanostructures are considered and their potential for enhancing quadrupole transitions is evaluated.

physics.optics↗

arXiv2025

Quantum interference of Rydberg excitons in Cu$_2$0: quantum beats

A density matrix formalism is employed to calculate the emission of multi-level excitonic system, highlighting picosecond-scale dynamics and coherent effects such as quantum beats. The results are compared with recent experimental results and indicate some directions of further study. In particular, the effect of Rydberg blockade on the quantum beat phenomenon is discussed.

physics.optics↗

arXiv2025

Optical properties of Rydberg excitons in Cu$_2$O based superlattices

Combining the microscopic calculation of superlattice minibands and the macroscopic real density matrix approach one can obtain electric susceptibilities of the superlattice system irradiated by an electromagnetical wave. It is shown how to compute the dispersion relation, excitonic resonances positions and susceptibility of Cu$_2$O/MgO based superlattice (SL), when Rydberg Exciton-Polaritons appear, including the effect of the coherence between the electron-hole pair and the electromagnetic field and the polaritonic effect. Using the Kronig-Penney model for computing miniband SL parameters the analytical expressions for optical functions are obtained and the numerical calculations for Cu$_2$O/MgO SL are performed.

physics.optics↗

arXiv2025

Optical to microwave frequency conversion with Rydberg excitons

A novel, copper-based plasmonic system is presented to provide optical to microwave photon conversion. The process uses highly excited levels in Cu2O Rydberg excitons and takes advantage of spoof plasmons, which allow for significant enhancement of the transition probability between specific excitonic energy levels. The theoretical results are verified with numerical simulations. The proposed system is very flexible, allowing for emission of microwaves wavelength from 0.1 mm to 10 mm.

physics.optics↗

arXiv2024

Optical properties of excitons in CdSe nanoplatelets and disks: real density matrix approach

We show how to calculate the optical functions of a nanoplatelet, taking into account the effect of a dielectric confinement on excitonic states. Real density matrix approach is employed to obtain analytical and semi-analytical relations for the absorption coefficient, the exciton resonance energy and binding energy of nanoplatelets and nanodisks. The impact of plate geometry (thickness, area) on the spectrum is discussed and the results are compared with the available experimental data.

physics.optics↗

arXiv2024

Two-photon absorption in silicon using real density matrix approach

Two-photon absorption in indirect gap semiconductors is an frequently encountered, but not well-understood phenomenon. To address this, the Real Density Matrix Approach is applied to describe two-photon absorption in silicon through the excitonic response to the interacting fields. This approach produces an analytical expression for the dispersion of the two-photon absorption coefficient for indirect-gap materials, and can be used to explain trends in reported experimental data for bulk silicon both old and new with minimal fitting.

physics.optics↗

arXiv2022

Copper plasmonics with excitons

We investigate the propagation of surface plasmons (SPPs) in a thin layer of copper surrounded by copper oxide Cu$_2$O. It is shown that particularly strong excitons in Cu$_2$O can have considerable impact on plasmon propagation, providing many opportunities for plasmon-exciton and plasmon-plasmon interactions. It is demonstrated that by the use of sufficiently thin metal layer, one can excite the so-called long range plasmons (LRSPPs) which can overcome the inherently high ohmic losses of Cu as compared to usual plasmonic metals such as silver. Analytical results are confirmed by numerical calculations.

cond-mat.mes-hall↗

arXiv2022

Nonlinear optical properties and Kerr nonlinearity of Rydberg excitons in Cu$_2$O quantum wells

The quantum confiment of Rydberg excitons (REs) in quantum structures opens the way towards considering nonlinear interactions in such systems. We present a theoretical calculation of optical functions in the case of a nonlinear coupling between REs in a quantum well with an electromagnetic wave. Using the Real Density Matrix Approach (RDMA), the analytical expressions for a linear and nonlinear absorption are derived and numerical calculations for Cu$_2$0 quantum wells are performed. The results indicate the conditions in which quantum well confinement states can be observed in linear and nonlinear optical spectra. The Kerr nonlinearity and self-phase modulation in such a system are studied. The effect of Rydberg blockade and the associated optical bleaching are also discussed and confronted with available experimental data.

cond-mat.mes-hall↗

arXiv2022

Self-Kerr effect across the yellow $\mathrm{Cu_2O}$ Rydberg series

We investigate the nonlinear refraction induced by Rydberg excitons in $\mathrm{Cu_2O}$. Using a high-precision interferometry imaging technique that spatially resolves the nonlinear phase shift, we observe significant shifts at extremely low laser intensity near each exciton resonance. From this, we derive the nonlinear index $\mathrm{n_2}$, present the $\mathrm{n_2}$ spectrum for $n\geq 5$ and report large $\mathrm{n_2}$ values of order $10^{-3}$ mm$^2$/mW. Moreover, we observe a rapid saturation of the Kerr nonlinearity and find that the saturation intensity $\mathrm{I_{sat}}$ decreases as $n^{-7}$. We explain this with the Rydberg blockade mechanism, whereby giant Rydberg interactions limit the exciton density, resulting in a maximum phase shift of 0.5 rad in our setup.

quant-ph↗

arXiv2021

Quantum confined Rydberg excitons in Cu$_2$O nanoparticles

The quantum confinement of Rydberg excitons is an important step towards exploiting their large nonlinearities for quantum applications. We observe Rydberg excitons in natural nanoparticles of Cu$_2$O. We resolve up to the principal quantum number $n=12$ in a bulk Cu$_2$O crystal and up to $n=6$ in nanoparticles extracted from the same crystal. The exciton transitions in nanoparticles are broadened and their oscillator strengths decrease as $\propto n^{-4}$ compared to those in the bulk (decreasing as $\propto n^{-3}$). We explain our results by including the effect of quantum confinement of exciton states in the nanoparticles. Our results provide an understanding of the physics of Cu$_2$O Rydberg excitons in confined dimensions.

cond-mat.mes-hall↗

arXiv2020

Rydberg Magnetoexcitons in Cu$_2$O Quantum Wells

We present theoretical approach that allows for calculation of optical functions for Cu$_2$O Quantum Well (QW) with Rydberg excitons in an external magnetic field of an arbitrary field strength. Both Faraday and Voigt configurations are considered, in the energetic region of p-excitons. We use the real density matrix approach and an effective e-h potential, which enable to derive analytical expressions for the QW magneto-optical functions. For both configurations, all three field regimes: weak, intermediate, and high field, are considered and treated separately. With the help of the developed approximeted method we are able to estimate the limits between the field regimes. The obtained theoretical magneto-absorption spectra show a good agreement with available experimental data.

cond-mat.mes-hall↗

arXiv2020

Excitons in Cu2O -- from Quantum Wells to Bulk Crystals and Additional Boundary Conditions for Rydberg Exciton-Polaritons

We propose a scheme for calculation of optical functions of a semiconductor with Rydberg excitons, for a wide interval of dimensions. We start with 2-dimensional structure, then going to thin films and ending on 3-dimensional bulk crystals. The calculations including the polaritons are performed, the case of large number of polariton branches is discussed and obtained theoretical absorption spectra show good agreement with experimental data.

cond-mat.mes-hall↗

arXiv2019

Nonlinear Optical Properties and Self-Kerr Effect of Rydberg Excitons in Cu$_2$O

We show how to compute the nonlinear optical functions (absorption, reflection, and transmission) for a medium with Rydberg excitons, including the effect of the coherence between the electron-hole pair and the electromagnetic field. Using the Real Density Matrix Approach the analytical expressions for nonlinear optical functions are obtained and numerical calculations for Cu$_2$0 crystal are performed. We report a good agreement with recently published experimental data. Propagation of the electromagnetic waves in Rydberg excitons media with nonliner effect is also discussed and the possibility of obtainig self-phase modulation due to Kerr nonlinearity is investigated.

cond-mat.mes-hall↗

arXiv2017

Electro-optical properties of Cu$_2$O in the regime of Franz-Keldysh oscillations

We present the analytical method enables one to compute the optical functions i.e., reflectivity, transmission and absorption including the excitonic effects for a semiconductor crystal exposed to a uniform electric field for energy region above the gap, for external field suitable to appearance of Franz-Keldysh (FK) oscillations. Our approach intrinsically takes into account the coherence between the carriers and the electromagnetic field. We quantitatively describe the amplitudes and periodicity of FK modulations and the influence of Rydberg excitons on FK effect is also taking into account. Our analytical findings are illustrated numerically for $P$ excitons in Cu$_2$O crystal.

cond-mat.mes-hall↗

arXiv2017

Ultraslow long-living plasmons with electromagnetically induced transparency

We analytically examine propagation of surface plasmon polaritons (SPPs) at a thin metallic film between glass substrate and electromagnetically-induced-transparency (EIT) medium. High-precision and high-resolution in frequency domain provided by EIT paves the way towards plasmonic group velocities reduction even by $4$ orders of magnitude and corresponding lifetime enhancement of SPPs up to microseconds.

physics.optics↗