Ultraviolet-induced absorption during very short continuous exposure in Ge-doped optical fiber

Ultraviolet-induced paramagnetic centers and absorption changes in singlemode Ge-doped optical fibers

“…2) can be interpreted as the tail of the absorption band ascribed to Ge(1), peaked at 4.5 eV with full width at half maximum of 0.9-1.3 eV. The slope represents the absorption cross section σ at 3.1 eV, σ 3.1 = ∆α 3.1 /N , where N is the total concentration [8,11,17,22,23,33]. We acknowledge that the agreement between fit and experimental data may be limited by the presence of other small contributions to induced absorbtion, not taken into account since we have fixed the intercept to zero.…”

“…The presence of H 2 gives rise also to the generation of H(II), known to be formed by reaction of hydrogen with GLPC. This can occur either by reaction of GLPC in ground state with H 0 produced by breaking of H 2 on paramagnetic centers [35], or by direct reaction of H 2 with GLPC in excited-triplet state [14,33]. The latter process leads to an observed reduction of lifetime of GLPC in excited triplet state in presence of H 2 [36]; since we have supposed the generation of Ge(1) to occur by two step absorption of GLPC via the long-lived triplet state, we expect a reduction of the Ge(1) formation rate in presence of hydrogen: this is consistent with the lower initial slope of the H 2 -loaded curve in Fig.…”

Luminescence spectroscopy of point defects in silica-based optical fibers

“…The irradiation source and our experimental set-up have been described in [5]. We also submitted this fiber (uncoated) to a CW ultraviolet (UV) transverse insolation at 244 nm (5 eV, fluence $127 J/cm 2 ), using a dedicated set-up [6]. We have previously performed ESR and absorption measurements, which showed that both types of irradiation lead to the same paramagnetic defects or absorbing defects in the spectral range 400-1700 nm [7].…”

Role of diffusing molecular hydrogen on relaxation processes in Ge-doped glass

“…For instance, some works revealed that under H 2 loading the ultraviolet (UV) transmittance is improved, because optical absorbing defects are suppressed by saturating dangling Si or O bonds with hydrogen. Moreover, the presence of H 2 improves by several orders of magnitude the photosensitivity [1][2][3][4][5][6]. From the microscopic point of view, photosensitivity has been partially associated with photochemical reactions involving the twofold-coordinated Ge (=Ge •• ) [1,[7][8][9][10][11][12], where the symbols '••' and '@' represent an electron lone pair and bonds with two distinct oxygen atoms, respectively.…”