arXiv subjects

Roman Antos

Publications and source records attributed to Roman Antos.

3 recordsLinked to original sources

arXiv2018

Investigation of the quality of an As35S65 grating by spectroscopic ellipsometry

The quality of an As35S65 chalcogenide glass (ChG) grating fabricated by electron beam lithography (EBL) was characterized by optical scatterometry based on spectroscopic ellipsometry (SE) in the visible and near infrared spectral range and complementary techniques providing direct images, especially atomic force microscopy (AFM). The geometric dimensions and the shape of patterned grating lines were determined by fitting modeled values (calculated by the Fourier modal method) to SE experimental data. A simple power-dependent function with only one variable parameter was successfully used to describe the shape of the patterned lines. The result yielded by SE is shown to correspond to AFM measurement with high accuracy, provided that optical constants of ChG modified by EBL were used in the fitting procedure. The line edge roughness (LER) of the grating was also investigated by further fitting the SE data to find out that no LER is optically detectable in the spectral range used, which is essential for the functionality of optical tools fabricated by EBL.

physics.optics↗

arXiv2010

Fourier factorization with complex polarization bases in the plane-wave expansion method applied to two-dimensional photonic crystals

We demonstrate an enhancement of the plane wave expansion method treating two-dimensional photonic crystals by applying Fourier factorization with generally elliptic polarization bases. By studying three examples of periodically arranged cylindrical elements, we compare our approach to the classical Ho method in which the permittivity function is simply expanded without changing coordinates, and to the normal vector method using a normal-tangential polarization transform. The compared calculations clearly show that our approach yields the best convergence properties owing to the complete continuity of our distribution of polarization bases. The presented methodology enables us to study more general systems such as periodic elements with an arbitrary cross-section or devices such as photonic crystal waveguides.

physics.optics↗

arXiv2009

Simulations of the dynamic switching of vortex chirality in magnetic nanodisks by a uniform field pulse

We present a possibility to switch the chirality of a spin vortex occurring in a magnetic nanodisk by applying a uniform in-plane field pulse, based on optimizing its strength and duration. The related spin-dynamical process, investigated by micromagnetic simulations, consists of several stages. After applying the field, the original vortex is expelled from the disk, after which two C-shaped states oscillate between each other. The essence of the method is based on turning the field off at a suitably chosen moment for which the orientation of the C-state will evolve into the nucleation of a vortex with the desirable chirality. This idea simply uses the information about the original chirality present inside the nanodisk during the dynamic process before losing it in saturation, and can thus be regarded as analogous to the recent studies on the polarity switching.

cond-mat.str-el↗