arXiv subjects

Stepan Ya. Vetrov

Publications and source records attributed to Stepan Ya. Vetrov.

9 recordsLinked to original sources

arXiv2024

Electrically controlled laser generation in a photonic crystal - liquid crystal - metal microcavity

A comprehensive approach for simulating lasing dynamics in a liquid crystal based laser is presented. The approach takes into account the transformation of the liquid crystal structure caused by applied voltage. In particular, it allows us to explicitly account for a resonant mode frequency shift in the laser equations. The laser dynamic is described by a set of coupled non-linear differential equations for dye polarizations, population densities and the electromagnetic fields. The proposed model is applied to a photonic crystal$-$metal microcavity filled with a resonant nematic liquid crystal layer doped with a dye. The calculated lasing spectra governed by external electric field are verified in comparison with measured spectra.

physics.optics↗

arXiv2021

Model of the Tamm plasmon polariton based solar cell

A model of an organic solar cell based on a Tamm plasmon polariton localized at the interface between a photonic crystal and a photosensitive layer with an embedded square or hexagonal plasmonic array has been proposed. The spectral properties of the structures have been investigated in the framework of the temporal coupled mode theory and confirmed by the transfer matrix method. It has been shown that the conjugation of a photonic crystal with a photosensitive layer leads to the excitation of a Tamm plasmon polariton at the interface between them and, consequently, to an increase in the integral absorption by 12% as compared with a planar solar cell without a photonic crystal.

physics.optics↗

arXiv2018

Chiral Optical Tamm States at the Interface between a Cholesteric and an All-Dielectric Polarization-Preserving Anisotropic Mirror

The chiral optical Tamm state is a new localized state of light at the interface between a polarization-preserving anisotropic mirror and an optically chiral medium such as a cholesteric liquid crystal. In this study the metal-free polarization-preserving mirror is used for efficient resonance control. We stress the advantage of the all-dielectric structure in obtaining high Q factor. The light is localized near the interface and the field decreases exponentially with the distance from the interface. The penetration of the field into the chiral medium is virtually blocked at wavelengths corresponding to the photonic band gap and close to the pitch of the helix. The polarization-preserving mirror has another photonic band gap as well. Our analytics agrees well with precise calculations, enabling intelligent design for laser and sensing applications.

physics.optics↗

arXiv2017

Tunable Hybrid Tamm-microcavity states

Spectral manifestations of hybrid Tamm-microcavity modes in a 1D photonic crystal bounded with a silver layer and containing a nematic liquid crystal layer working as a microcavity have been studied using numerical simulation. It is demonstrated that the hybrid modes can be effectively tuned owing to the high sensitivity of the liquid crystal to the temperature and external electric field variations. It is established that the effect of temperature on the transmission spectrum of the investigated structure is most pronounced at the point of the phase transition of the liquid crystal to the isotropic state, where the refractive index jump is observed.

physics.optics↗

arXiv2017

Chiral Optical Tamm States: Temporal Coupled-Mode Theory

The chiral optical Tamm state (COTS) is a special localized state at the interface of a handedness-preserving mirror and a structurally chiral medium such as a cholesteric liquid crystal or a chiral sculptured thin film. The spectral behavior of COTS, observed as reflection resonances, is described by the temporal coupled-mode theory. Mode coupling is different for two circular light polarizations because COTS has a helix structure replicating that of the cholesteric. The mode coupling for co-handed circularly polarized light exponentially attenuates with the cholesteric layer thickness since the COTS frequency falls into the stop band. Cross-handed circularly polarized light freely goes through the cholesteric layer and can excite COTS when reflected from the handedness-preserving mirror. The coupling in this case is proportional to anisotropy of the cholesteric and theoretically it is only anisotropy of magnetic permittivity that can ultimately cancel this coupling. These two couplings being equal results in a polarization crossover (the Kopp--Genack effect) for which a linear polarization is optimal to excite COTS. The corresponding cholesteric thickness and scattering matrix for COTS are generally described by simple expressions.

physics.optics↗

arXiv2016

Chiral optical Tamm states at the boundary of the medium with helical symmetry of the dielectric tensor [In Russian]

A new optical state is described both analytically and numerically at the boundary of a chiral medium with continuous helical symmetry of the dielectric tensor. The tangential wave number is assumed to be zero. The state appears to be localized near the boundary. It does not transfer energy along this boundary and falls off exponentially with the distance from the boundary. The field penetration into chiral medium is blocked at wavelengths close to the helical pitch and corresponding to the photonic band gap. The polarization of light near the boundary has the same sign of chirality as the helical medium. It is shown that the homogeneous environment, or the substrate must exhibit the anisotropic metallic reflection. Spectral manifestation of the state is determined by the angle between the optical axes at the interface. A realistic example is considered at the boundary of a cholesteric liquid crystal and a metal-dielectric anisotropic nanocomposite.

physics.optics↗

arXiv2016

Spectral and polarization properties of 'cholesteric liquid crystal - phase plate - metal' structure

We investigate the localized surface modes in a structure consisting of the cholesteric liquid crystal layer, a phase plate, and a metal layer. These modes are analogous to the optical Tamm states. The nonreciprocal transmission of polarized light propagating in the forward and backward directions is established. It is demonstrated that the transmission spectrum can be controlled by external fields acting on the cholesteric liquid crystal and by varying the plane of polarization of the incident light. [The text is presented both in English (pp 1-9) and in Russian (pp 10-19)]

physics.optics↗

arXiv2014

Photonic defect modes in cholesteric liquid crystal with a resonant nanocomposite layer and a twist defect

We have studied spectral properties of a cholesteric liquid crystal with a combined defect consisting of a nanocomposite layer and a twist. The nanocomposite layer is made of metallic nanoballs dispersed in a transparent matrix and featuring effective resonant permittivity. A solution has been found for the transmission spectrum of circularly polarized waves in the structure. We have analyzed spectral splitting of the defect mode in the bandgap of the cholesteric when its frequency coincides with the nanocomposite resonant frequency. Defect modes have characteristics strongly dependent on the magnitude and direction of the phase jump at the interface between nanocomposite and cholesteric layers. It has been found that the bandgap width and the position and localization degree of defect modes can be effectively controlled by external fields applied to cholesteric.

physics.optics↗

arXiv2011

Voltage-induced defect mode interaction in a one-dimensional photonic crystal with a twisted-nematic defect layer

Defect modes are investigated in a band gap of an electrically tunable one-dimensional photonic crystal infiltrated with a twisted-nematic liquid crystal (1D PC/TN). Their frequency shift and interference under applied voltage are studied both experimentally and theoretically. We deal with the case where the defect layer thickness is much larger than the wavelength (Mauguin condition). It is shown theoretically that the defect modes could have a complex structure with the elliptic polarization. Two series of polarized modes interact with each other and exhibit an avoided crossing phenomenon in the case of opposite parity.

physics.optics↗