Stability of E′ centers induced by 4.7eV laser radiation in SiO2

Abstract

The kinetics of E' centers (≡Si•) induced by 4.7eV pulsed laser irradiation in dry fused silica was investigated by in situ optical absorption spectroscopy. The stability of the defects, conditioned by reaction with mobile hydrogen of radiolytic origin, is discussed and compared to results of similar experiments performed on wet fused silica. A portion of E' and hydrogen are most likely generated by laser-induced breaking of Si-H precursors, while an additional fraction of the paramagnetic centers arise from another formation mechanism. Both typologies of E' participate to the reaction with H 2 leading to the post-irradiation decay of the defects. This annealing process is slowed down on decreasing temperature and is frozen at T=200K, consistently with the diffusion properties of H 2 in silica.

Nanogratings in fused silica: Formation, control, and applications

“…This is in accordance with the temperature dependent decay of E 0 -centers reported by Messina and Cannas. 49 Whereas at 200 K the concentration of E 0 -centers remains constant in time, at 300 K these defects are subject to decay. In contrast, NBOHCs are stable after an initial decay due to hydrogen recombination.…”

Annihilation of E′ center defects in silica glass by hydrogen treatment

“…The decay of radiation-induced E 0 center in wet and dry silica glass was investigated and it was suggested that the reaction (1) is the mechanism of the decay of E 0 center [5,6]. In this paper attention is focused on the reaction shown in Eq.…”

“…It is also known that pre-treatment of silica glasses with hydrogen before irradiation reduces the optical property degradation caused by defect creation by irradiation [3,4]. It was also suggested [5,6] that post UV irradiation annealing of E 0 center was effected by hydrogen produced during the UV irradiation. In this paper, the effect of hydrogen treatment at high temperature on the concentration of E 0 centers in silica glass is reported.…”

Temperature dependence of the generation and decay of E′ centers induced in silica by 4.7eV laser radiation

“…An important feature of the E 0 center, shared by other paramagnetic defects, is that it can be annealed by reaction with diffusing H 2 [10,12,[14][15][16][17][18][19][20]. This process is widely exploited in optical fibers technology where H 2 loading of the SiO 2 core material is used to prevent it from being damaged by UV light.…”

“…Since passivation of E 0 by H 2 is thermally activated as well, the presence of hydrogen may be expected to influence the temperature dependence of the formation efficiency of the defects, due to the interplay between generation and passivation. To thoroughly investigate this issue it is needed to measure in situ the kinetics of the defects in temperature-controlled experiments [16,[18][19][20], in contrast with previous works that measured only the stationary concentration of E 0 centers [4,5,[8][9][10][11] …”