arXiv subjects

David Ziemkiewicz

Publications and source records attributed to David Ziemkiewicz.

35 records · Page 2Linked to original sources

arXiv2021

Numerical analysis of grasshopper escapement

The dynamics of driven, damped pendulum as used in mechanical clocks is numerically investigated. In addition to the analysis of a well-known mechanisms such as chronometer escapement, the unusual properties of Harrison's grasshopper escapement are explored, giving some insights regarding the dynamics of this system. Both steady state operation and transient effects are discussed, indicating the optimal condition for stable long-term clock accuracy. Possibility of chaotic motion is investigated.

physics.class-ph↗

arXiv2021

Fractional Derivative Modification of a Drude Model

A modification of the Drude dispersive model based on fractional time derivative is presented. The dielectric susceptibility is calculated analytically and simulated numerically, showing a good agreement between theoretical description and numerical results. The absorption coefficient and wave vector -- key parameters describing the propagation of waves in such a medium -- are shown to follow a power law in the frequency domain, which is a common phenomenon in many real life applications. The introduction of two separate parameters provides a more flexible model than some other approaches found in literature and is well suited for numerical implementation.

physics.comp-ph↗

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↗

arXiv2017

Tunable narrow-band plasmonic resonances in electromagnetically-induced-transparency media

The spectral response of a plasmonic nanostructure may heavily depend on the refractive index of its surroundings. The key idea of this paper is to control this response by coherent optical means, i.e. with an optically controlled electromagnetically-induced-transparency medium. In such environment, an external laser provides a knob to shift the position of plasmonic resonances without the need to change the geometry of the nanostructure. Additionally, the setup can be exploited to excite narrow-band surface plasmon polaritons.

physics.optics↗

arXiv2016

Simple analytic equation for airfoil shape description

We show a simple, analytic equation describing a class of two-dimensional shapes well suited for representation of aircraft airfoil profiles. Our goal was to create a description characterized by a small number of parameters with easily understandable meaning, providing a tool to alter the shape with optimization procedures as well as manual tweaks by the designer. The generated shapes are well suited for numerical analysis with 2D flow solving software such as XFOIL.

physics.flu-dyn↗

arXiv2016

Electromagnetically Induced Transparency and slow light in media with Rydberg Excitons

We show that the Electromagnetically Induced Transparency (EIT) is possible in a medium exhibiting Rydberg excitons and indicate the realistic parameters to perform the experiment. The calculations for a Cu$_2$O crystal are given which show that in this medium due to large group index one could expect slowing down a light pulse by a factor about $10^4$.

quant-ph↗

arXiv2016

Magnetooptical Properties of Rydberg Excitons - Center-of-Mass Quantization Approach

We show how to compute the magnetooptical functions (absorption, reflection, and transmission) 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 Real Density Matrix Approach the analytical expressions for magnetooptical functions are obtained and numerical calculations for Cu$_2$0 crystal are performed. The influence of the strength of applied external magnetic field on the resonance displacement of excitonic spectra is discussed. We report a good agreement with recently published experimental data.

cond-mat.mes-hall↗

arXiv2016

Electrooptical Properties of Rydberg Excitons

We show how to compute the electrooptical functions (absorption, reflection, and transmission) when Rydberg Excitons appear, including the effect of the coherence between the electron-hole pair and the electromagnetic field. With the use of Real Density Matrix Approach numerical calculations applied for Cu$_2$0 crystal are performed. We also examine in detail and explain the dependence of the resonance displacement on the state number and applied electric field strength. We report a good agreement with recently published experimental data.

cond-mat.mes-hall↗

arXiv2015

Optical Properties of Rydberg Excitons and Polaritons

We show how to compute the optical functions when Rydberg Excitons appear, including the effect of the coherence between the electron-hole pair and the electromagnetic field. We use the Real Density Matrix Approach (RDMA), which, combined with Green's function method, enables one to derive analytical expressions for the optical functions. Choosing the susceptibility, we performed numerical calculations appropriate to a Cu$_2$0 crystal. The effect of the coherence is displayed in the line shape. We also examine in details and explain the dependence of the oscillator strength and the resonance placement on the state number. We report a good agreement with recently published experimental data.

cond-mat.mes-hall↗

arXiv2015

Quantum Confined Stark Effect in Wide Parabolic Quantum Wells

We show how to compute the optical functions of Wide Parabolic Quantum Wells (WPQWs) exposed to uniform electric F applied in the growth direction, in the excitonic energy region. The effect of the coherence between the electron-hole pair and the electromagnetic field of the propagating wave including the electron-hole screened Coulomb potential is adopted, and the valence band structure is taken into account in the cylindrical approximation. The role of the interaction potential and of the applied electric field, which mix the energy states according to different quantum numbers and create symmetry forbidden transitions, is stressed. We use the Real Density Matrix Approach (RDMA) and an effective e-h potential, which enable to derive analytical expressions for the WPQWs electrooptical functions. Choosing the susceptibility, we performed numerical calculations appropriate to a GaAs/GaAlAs WPQWs. We have obtained a red shift of the absorption maxima (Quantum Confined Stark Effect), asymmetric upon the change of the direction of the applied field (F -> -F), parabolic for the ground state and strongly dependent on the confinement parameters (the QWs sizes), changes in the oscillator strengths, and new peaks related to the states with different parity for electron and hole.

cond-mat.mes-hall↗

arXiv2015

Combined complex Doppler and Cherenkov effect in left-handed metamaterials

We derive the formula of the complex Doppler shift in a two-dimensional, dispersive metamaterial and we show that a moving, monochromatic radiation source generates multiple frequency modes. The role of the group velocity is stressed and the Doppler shifted radiation field exhibits features of the Cherenkov effect. The presented theory is also applicable to the case of a moving, nonoscillating charge and explains many peculiar characteristics of the Cherenkov radiation in lefthanded metamaterials such as the backward direction of power emission, the constant radiation angle and the lack of velocity threshold.

physics.optics↗

arXiv2015

Excitonic Spectra of Wide Parabolic Quantum Wells

The optical properties of wide Quantum Wells are considered, taking into account the screened electron-hole interaction potential and parabolic confinement potentials, different for the electrons and for the holes. The role of the interaction potential which mixes the energy states according to different quantum numbers is stressed. The results obtained by our method are in agreement with the observed spectra and give the possibility to the assessment of the resonances.

cond-mat.mes-hall↗

arXiv2014

Complex Doppler effect in left-handed metamaterials

The Doppler shift is investigated in one-dimensional system with moving source. Theoretical findings are confirmed in numerical simulations of optical and acoustical waves propagation in simple metamaterial model, showing the reversed shift and the existence of multiple frequency modes. The properties of these waves are discussed. The effect of absorption on the phenomenon is outlined.

physics.optics↗