The vibrational states of photoinduced defects in silica fibers

Александров, И. В.; Nesterova, Z. V.; Petrovskiĭ, G. T.

doi:10.1016/0022-3093(94)90375-1

Cited by 7 publications

(14 citation statements)

References 11 publications

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“…In addition to the fundamental band, an overtone and combination 440 + 570 cm À1 band are detected. It has been established that a growth dynamics for the 490 cm À1 band intensity strongly correlates with decreasing 570 cm À1 band intensity [12]. In contrast to the Ge-doped fiber sample discussed here, earlier we used a relatively weakly doped Ge-doped fiber where the fundamental SRS band included the 490 cm À1 band as a shoulder [12].…”

Section: Resultsmentioning

confidence: 94%

“…To assign SRS bands more reliably, it is useful to compare the SRS spectra of non-irradiated silica fibers and the fibers capable of SHG due to the presence of an ordered photoinduced colour center structure in a fiber core. The SRS spectra for the latter were obtain earlier [12]. Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The photoinduced changes and visible SHG radiation in germanium-doped silica fibers were ensured by using the experimental procedure reported earlier [12]. Namely, a monomode (at k % 850 nm) Ge-doped fiber was irradiated by intense IR pulses (k = 1.06 lm) with a peak power of $20 kW and repetition rate of $5 kHz.…”

Section: Methodsmentioning

confidence: 99%

“…These bands can be caused by silica tetrahedron vibrations, the vibrations of the so-called ÔdefectÕ groups, and dopant vibrations [11]. Later, the intense SRS Stokes bands originating from photoinduced colour centers capable of effective SHG in silica fibers were observed and interpreted [12]. Some practical applications of SRS spectroscopy in fibers were demonstrated [11].…”

Section: Introductionmentioning

confidence: 97%

“…In our previous studies, the fundamental spectroscopic aspects of multiple-cascade SRS excitation in silica-based fibers using high-power picosecond pulse laser pumping were formulated and some practical applications of nonlinear SRS spectroscopy in fibers were demonstrated [10][11][12]. It was pointed out that the SRS spectroscopy in fibers is a powerful technique for glass microstructural studies using definite correlations between the anharmonicity constants and the SRS Stokes bandwidths.…”

Section: Introductionmentioning

confidence: 97%

See 4 more Smart Citations

Medium-range ordering in glass structures as a background of photosensitivity in silica fibers

Nesterova

Melchor

Alexandrov

2005

Journal of Non-Crystalline Solids

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Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 97%

See 3 more Smart Citations

Medium-range ordering in glass structures as a background of photosensitivity in silica fibers

Nesterova

Melchor

Alexandrov

2005

Journal of Non-Crystalline Solids

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Evidence of microscopic-scale modifications in optical glasses supporting second harmonic generation

et al. 1998

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We explore, by means of inelastic neutron scattering, the extent of changes in dynamic correlations induced by thermal poling of vitreous SiO2. The measured vibrational density of states shows an excess of modes in certain frequency regions as well as a narrowing of the 100 meV peak. These findings indicate that such alterations cannot be ascribed to the appearance of new well defined vibrational modes, such as those coming from localized topological defects, but rather arises from an increase in ordering in the material as attested in a reduced spread of the inter-tetrahedral angles.

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Emergence of Structural Anisotropy in Optical Glasses Treated to Support Second Harmonic Generation

et al. 1998

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Structural alterations in v-SiO2 induced by "thermal poling", a treatment which makes the glass able to double the frequency of an impinging infrared light, are revealed by neutron diffraction as a breakdown of the macroscopic isotropy. This leads to concomitant changes in the vibrational density of states measured by inelastic neutron scattering. The observations are found to be consistent with the emergence of partial ordering within the glassy matrix along the direction of an electrostatic field applied during the poling treatment. 42.70.Ce, 42.65.Ky Few discoveries have puzzled the optics community more than the emergence of visible (green) light from optical fibers after strong irradiation by an infrared laser [1]. This frequency-doubling phenomenon known as Second Harmonic Generation (SHG) is not expected to take place in a centrosymmetric material such as the amorphous silica fiber-core, which shows no measurable second-order optical susceptibility χ (2) [2]. The process to be efficient also requires well defined phase-matching between the interacting waves to allow for constructive interference, and this seems even more difficult to fulfill within the glassy medium. Several plausible explanations about the origin of the phenomenon have been put forward. One of the most widely accepted [3] does not involve structural modifications to accomplish the breakdown of the glass radial symmetry. Rather, it postulates the emergence of a spatially modulated local dc field, E 0 , which, via a third-order nonlinearity (χ (3) ) (finite in isotropic materials), induces a spatially modulated second order nonlinearity (χ (2) ∝ χ (3) E 0 ) able to double the pump frequency. The achievement of a permanent χ (2) in optical glasses has focused a large research effort, which lead to the discovery of alternative poling techniques. In actual fact, the phenomenon can be produced by application of a high voltage (∼ 5 kV, just below dielectric breakdown) to glass plates at moderate temperatures (∼ 540 K − 580 K, compared with ≈ 1475 K where the glass melts). This method, known as "thermal" poling [4], provides permanent second-order nonlinear responses comparable to those shown by inorganic crystals. Whether the mechanism(s) leading to the emergence of a second order nonlinearity in "thermally-poled" glasses differ from those of photoinduced SHG or not needs to be clarified. At any rate, the relevant point stems from the possibility this method has opened up for developing inexpensive integrated optical frequency converters and electro-optic modulators.Up to now studies on the microscopic structure and/or dynamical alterations associated with poling are scarce. Significant changes between poled and native fibers at rather well defined frequencies have been reported from Raman studies [5]. Direct interpretation of such Raman data is however hampered by the need of knowledge of the possible structural alterations in order to assess the concomitant variations in the Raman matrix elements governing the signal intensities. Here we ...

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The vibrational states of photoinduced defects in silica fibers

Cited by 7 publications

References 11 publications

Medium-range ordering in glass structures as a background of photosensitivity in silica fibers

Medium-range ordering in glass structures as a background of photosensitivity in silica fibers

Evidence of microscopic-scale modifications in optical glasses supporting second harmonic generation

Emergence of Structural Anisotropy in Optical Glasses Treated to Support Second Harmonic Generation

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