arXiv subjects

Alexander B. Pevtsov

Publications and source records attributed to Alexander B. Pevtsov.

3 recordsLinked to original sources

arXiv2021

Material and radiation losses in structures with bound states in the continuum: Ge2Sb2Te5 as an example

The problem of losses in resonators is a key issue in the design and use of modern plasmonic and photonic meta-devices. We propose a spectroscopic method for determining material and radiation losses in structures with bound states in the continuum using as example the phase-change chalcogenide Ge2Sb2Te5. The complex refractive index for the amorphous and crystalline Ge2Sb2Te5 phases was measured experimentally, and the resonance optical properties were calculated for a telecommunication wavelength of 1500 nm. To demonstrate the validity of the method, two types of resonators were considered - a cylinder and a ring which support bound states in the continuum according to the Friedrich - Wintgen mechanism. We have determined the value of the material quality-factor for the amorphous Ge2Sb2Te5 as Qmat = 46 and the values of the radiation quality-factors Qrad = 608 for the cylinder and Qrad = 332 for the ring of a pair of TE0,1,2 and TE0,2,0 modes in the regime of bound states in the continuum. We also demonstrated two mechanisms for efficient switching of the scattering spectra between the amorphous and crystalline phases of Ge2Sb2Te5.

physics.optics↗

arXiv2017

Effect of photonic crystal stop-band on photoluminescence of $a$-Si$_{1-x}$C$_x$:H

Effects associated with the change in the local density of photonic states in a periodic structure based on alternating \textit{a}-Si$_{1-x}$C$_x$:H and \textit{a}-SiO$_2$ amorphous layers forming a one-dimensional (1D) photonic crystal have been analyzed. The use of \textit{a}-Si$_{1-x}$C$_x$:H as the emitting material made it possible to examine the transformation of the photoluminescence spectrum contour that is comparable in width with the photonic stop-band. It was experimentally demonstrated that the emission is enhanced and suppressed in the vicinity of the stop-band. The relative intensities of the luminescence peaks at different edges of the stop-band vary with the detuning of the stop-band position and photoluminescence peak of a single \textit{a}-Si$_{1-x}$C$_x$:H film. The Purcell effect in the system under consideration was theoretically described by the method in which the local density of photonic states is calculated in terms of a 1D model. %A good agreement was obtained between the experimentally measured and calculated spectra. It was shown that the specific part of local density of states substantially increases at the long-wavelength (low-frequency) edge of the stop-band of a 1D photonic crystal as a result of the predominant localization of the electric field of the light wave in the spatial regions of \textit{a}-Si$_{1-x}$C$_x$:H which have a higher relative permittivity as compared with \textit{a}-SiO$_2$.

cond-mat.mes-hall↗

arXiv2017

Optical properties of opaline photonic crystals covered by phase-change material Ge$_2$Sb$_2$Te$_5$

The physical origin of resonant Wood's anomalies in the reflection spectra of three-dimensional (3D) opaline photonic crystals covered with Ge$_2$Sb$_2$Te$_5$ (GST225) is discussed. For this purpose, the optical reflection spectra are studied for different incident angles of light both experimentally and theoretically. The performed eigenmode analysis reveals that the Wood's anomalies originate from the quasiguided modes which appear in the GST225 capping layer. This conclusion is supported by the simulated electromagnetic near-field distributions of incident light at resonant frequencies. The experimental reflection spectra are in a good agreement with theoretical calculations performed by the Fourier modal method in the scattering matrix form.

physics.optics↗