arXiv subjects

Sergey A. Tarasenko

Publications and source records attributed to Sergey A. Tarasenko.

7 recordsLinked to original sources

arXiv2026

Twist tunable resonances in photonic bilayer for second harmonic generation

Moiré structure emerging in photonic bilayers stacked with a twist enables the controllable frequency selective resonant response. Here, we employ twist tunable resonances to boost second harmonic generation (SHG) at a desired frequency in twisted photonic bilayers integrated with two-dimensional nonlinear crystals. We develop an analytical theory relating the resonance frequencies and the SHG enhancement factor to the material parameters of the dielectric layers and the twist angle. The theory reveals a critical twist angle separating two distinct regimes of photonic bilayer operation: with open and closed moiré diffraction channels. Above the critical angle, the photon leakage from the guided mode is suppressed and the SHG enhancement factor rises by orders of magnitude. The paper offers a compact route to nonlinear conversion in moiré photonic structures efficient and tunable over a wide spectral range.

physics.optics↗

arXiv2025

Resonant enhancement of second harmonic generation in 2D nonlinear crystal integrated with meta-waveguide: analytical vs numerical approaches

We present an analytical theory of second harmonic generation (SHG) in hybrid structures combining a nonlinear 2D crystal with a dielectric metasurface waveguide. The theory describes the excitation spectrum and enhancement of SHG at both leaky mode and quasi-bound state in the continuum (quasi-BIC) resonances in terms of the material parameters. For low-loss systems, the SHG efficiency at leaky resonances is determined by their radiative broadening, governed by the relevant Fourier harmonics of the metasurface polarizability, whereas the SHG enhancement at quasi-BIC resonances is ultimately limited by inhomogeneous broadening and absorption in the system. We also describe the emergence and polarization properties of second harmonic diffracted beams. These beams appear even if both the 2D crystal and the meta-waveguide are centrosymmetric owing to the nonlocal mechanism of SHG. The developed framework provides a systematic theoretical basis for optimizing the resonant nonlinear frequency conversion in hybrid 2D-material-metasurface platforms and identifies the fundamental limitations of the SHG efficiency.

physics.optics↗

arXiv2024

Emergent spin and orbital angular momentum of light in twisted photonic bilayer

We demonstrate that the optical response of twisted photonic bilayers, photonic counterparts of van der Waals structures, is sensitive to both spin angular momentum (SAM) and orbital angular momentum (OAM) of light. A beam of unpolarized light with zero angular momentum acquires SAM in transmission and OAM in reflection. The developed analytical theory and numerical calculations show that the SAM and OAM arise from distinct microscopic mechanisms and depend differently on the interlayer distance. The predicted phenomena do not require light absorption and are caused by the photon-helicity-dependent light diffraction by the moiré pattern, which inevitably occurs in the twisted structure, and the SAM-OAM conversion processes. We also reveal strong SAM and OAM in the moiré-diffracted beams. Our findings uncover a profound connection between the emergent SAM and OAM in twisted photonic systems offering new possibilities for angular-momentum-resolved light-matter interactions.

physics.optics↗

arXiv2017

Optical activity in chiral stacks of 2D semiconductors

We show that the stacks of two-dimensional semiconductor crystals with the chiral packing exhibit optical activity and circular dichroism. We develop a microscopic theory of these phenomena in the spectral range of exciton transitions which takes into account the spin-dependent hopping of excitons between the layers in the stack and the interlayer coupling of excitons via electromagnetic field. For the stacks of realistic two-dimensional semiconductors such as transition metal dichalcogenides, we calculate the rotation and ellipticity angles of radiation transmitted through such structures. The angles are resonantly enhanced at the frequencies of both bright and dark exciton modes in the stack. We also study the photoluminescence of chiral stacks and show that it is circularly polarized.

cond-mat.mes-hall↗

arXiv2017

Fluid photonic crystal from colloidal quantum dots

We study optical forces acting upon semiconductor quantum dots and the force driven motion of the dots in a colloid. In the spectral range of exciton transitions in uantum dots, when the photon energy is close to the exciton energy, the polarizability of the dots is drastically increased. It leads to a resonant increase of both the gradient and the scattering contributions to the optical force, which enables the efficient manipulation with the dots. We reveal that the optical grating of the colloid leads to the formation of a fluid photonic crystal with spatially periodic circulating fluxes and density of the dots. Pronounced resonant dielectric response of semiconductor quantum dots enables a separation of the quantum dots with different exciton frequencies.

cond-mat.mes-hall↗

arXiv2015

Ultrafast magneto-photocurrents in GaAs: Separation of surface and bulk contributions

We induce ultrafast magneto-photocurrents in a GaAs crystal employing interband excitation with femtosecond laser pulses at room temperature and non-invasively separate surface and bulk contributions to the overall current response. The separation between the different symmetry contributions is achieved by measuring the simultaneously emitted terahertz radiation for different sample orientations. Excitation intensity and photon energy dependences of the magneto-photocurrents for linearly and circularly polarized excitations reveal an involvement of different microscopic origins, one of which we believe is the inverse Spin-Hall effect. Our experiments are important for a better understanding of the complex momentum-space carrier dynamics in magnetic fields.

physics.optics↗

arXiv2006

Zero-bias spin separation

Spin-orbit coupling provides a versatile tool to generate and to manipulate the spin degree of freedom in low-dimensional semiconductor structures. The spin Hall effect, where an electrical current drives a transverse spin current and causes a nonequilibrium spin accumulation observed near the sample boundary, the spin-galvanic effect, where a nonequilibrium spin polarization drives an electric current, or the reverse process, in which an electrical current generates a nonequilibrium spin polarization, are all consequences of spin-orbit coupling. In order to observe a spin Hall effect a bias driven current is an essential prerequisite. The spin separation is caused via spin-orbit coupling either by Mott scattering (extrinsic spin Hall effect) or by Rashba or Dresselhaus spin splitting of the band structure (intrinsic spin Hall effect). Here we provide evidence for an elementary effect causing spin separation which is fundamentally different from that of the spin Hall effect. In contrast to the spin Hall effect it does not require an electric current to flow: It is spin separation achieved by spin-dependent scattering of electrons in media with suitable symmetry. We show that by free carrier (Drude) absorption of terahertz radiation spin separation is achieved in a wide range of temperatures from liquid helium up to room temperature. Moreover the experimental results give evidence that simple electron gas heating by any means is already sufficient to yield spin separation due to spin-dependent energy relaxation processes of nonequilibrium carriers.

cond-mat.other↗