Electron irradiation induced reduction of the permittivity in chalcogenide glass (As2S3) thin film

Abstract

In this paper we investigate the effect of electron beam irradiation on the dielectric properties of As 2 S 3 Chalcogenide glass. By means of low-loss Electron Energy Loss Spectroscopy, we derive the permittivity function, its dispersive relation, and calculate the refractive index and absorption coefficients under the constant permeability approximation. The measured and calculated results show a heretofore unseen phenomenon: a reduction in the permittivity of ≥ 40%. Consequently a reduction of the refractive index of 20%, hence suggesting a conspicuous change in the optical properties of the material under irradiation with a 300 keV electron beam. The plausible physical phenomena leading to these observations are discussed in terms of the homopolar and heteropolar bond dynamics under high energy absorption. The reported phenomena, exhibited by As 2 S 3 -thin film, can be crucial for the development of photonics integrated circuits using electron beam irradiation method.

All-dielectric phase-change reconfigurable metasurface

“…The induced index change of $10% is substantial but yet smaller and less wavelength-dependent than may be expected on the basis of ellipsometric data for unstructured crystalline GST. 33 This indicates strongly that the nanostructured GST is stoichiometrically modified and/or only partially crystallized, 5,36,37 which is to be anticipated primarily as a consequence of the FIB milling process (reduction of refractive index due to irradiation, 38 creation of defects and gallium implantation) and because nanostructuring unavoidably modifies the thermal properties of the film (i.e., the energy absorbed from the laser beam at a given point; the temperature achieved; and the rates of temperature increase/ decrease).…”

Photonic analogies of gravitational attractors

“…Centro-symmetrical refractive index like the one just described brings an interesting opportunity since they can be fabricated for example by stacking different photo-refractive [meta]materials in multiple layers. Recall that in photorefraction the optical properties of the material, permeability and permittivity, change as a function of the light intensity, allowing the fabrication of a continuously varying refractive index as the one required by a Gaussian-like attractor [8], [?]. Moreover, since photo-refractivity is elastic, it allows to modify the refractive index of the layers combined in time, thence enabling or disabling the trap at will.…”

Investigation of a chalcohalide glass optical waveguide structure fabricated by dual-energy carbon-ion implantation

“…The main advantage of these materials is that they can transmit across a wide range of the infrared electromagnetic spectrum [6]. Chalcohalide glasses are also ideal alternative materials for incorporation into lasers, planar optics, photonic integrated circuits, and other active devices, especially when doped with rare Earth ions because of the properties of chalcohalide glasses, such as high refractive indices, low phonon energies, and high nonlinearities (photon-induced refraction and electron-induced permittivity modification) [1,6,7]. Furthermore, chalcohalide glasses show the largest χ 3 (third-order nonlinearity) among inorganic glasses (approximately two to three orders of magnitude greater than that of silica) due to their large atomic weights, leading to SHG efficiency [8][9][10][11].…”