Mechanism of photoinduced anisotropy in chalcogenide glasses

Abstract

Structural and optical anisotropies have been investigated in some chalcogenide glasses exposed to illumination of linearly polarized light. X-ray diffraction patterns of illuminated As 2 S 3 manifest a structural modification at ϳ1 Å Ϫ1. Photoinduced birefringence in As 2 S 3 becomes maximal at some temperature, which is higher for illumination with a lower photon energy. The photoinduced birefringence becomes greater in the order of As 2 Se 3 , As 2 S 3 , and Se, which is the same with the order of the natural birefringence in the corresponding crystals. These observations suggest that the photoinduced anisotropy arises from orientation of quasicrystalline clusters. The model is compared with photoinduced anisotropies observed in other materials.

High-performance Bragg gratings in chalcogenide rib waveguides written with a modified Sagnac interferometer

“…Even though photoinduced birefringence of the order of ⌬n ϳ 2 ϫ 10 −3 has been previously observed in As 2 S 3 illuminated by bandgap light ͑E ϳ 2.3 eV͒ (Ref. 36) and a nonuniform refractive index profile in the vertical direction may be expected from the limited absorption length for the 532 nm writing wavelength 16 (ϳ3 m, comparable to our waveguide dimensions), we have observed varied spectral splitting even under identical writing conditions. This suggests other mechanisms, such as stress-induced anisotropy (induced possibly under waveguide fabrication), are present.…”

Investigation of anisotropy in as-evaporated amorphous chalcogenide thin films by optical waveguiding

“…That is, for As 2 S 3 Dn ¼ À0:02, and, on the other hand, the crystal birefringence is )0.5 [22]. The conventional photoinduced birefringence of the amorphous films is $1/10 of the former and $1/ 100 of the latter [8,22].…”

“…polarization mode convertors in optical fibers. As a result of renewed interests, a number of systems have been investigated and different models have been proposed to account for the observed anisotropies: based on the intrinsic negative-U charged defects of the chalcogenides [6], on the orientation of normal bonding orbitals [7], and on the basis of more extended structural species [8]. Because of uncertainties in the underlying physical mechanisms of the phenomenon, reasonably there exists a need for more experimental data to help our understanding of this unique effect.…”

ELECTRICAL AND PHOTOELECTRICAL PROPERTIES OF A-Ge20Te80-xBix (x = 0, 1.5, 2.5, 5.0) THIN FILMS

“…The interest in these materials arises particularly due to their ease of fabrication in the form of bulk and thin films. Furthermore, one can easily change the properties of these glasses by varying their chemical composition (synthesis regime) [4,5] or irradiating them by light (photoinduced phenomena) [6][7][8]. A typical chalcogenide has a relatively sharp optical absorption edge, a single electrical activation energy and efficient photoexcited conductivity and luminescence.…”