Germanium-doped Silica Glass Research Articles

Design of single-mode single-circularly polarized chiral anti-resonant fiber for the communication band

We propose a design of anti-resonant fiber (ARF) involving the introduction of chiral material into the inner regions of six germanium-doped silica glass cladding tubes, which can support the operation of single-mode single left-handed circular polarization in the communication band from 1.540 to 1.605 µm. In particular, the loss reaches a minimum value of 0.009 dB m−1 at 1.550 µm. The sign of the chiral parameter can control the handedness of polarization in the operation of single-mode single-circular polarization. In addition, the ARF possesses a good bending resistance performance. The minimum bending radius of the ARF is 10 to maintain the single-mode single left-handed circular polarization for 1.550 µm. We believe the novel ARF can find applications in optical communication, polarization imaging and chiral sensing.

Supercontinuum generation in nanostructured core gradient index fibers

We report on near-infrared supercontinuum generation in a submeter-long single-mode, nanostructured core fiber. The fiber core is composed of few thousand pure silica and germanium-doped silica glass nanorods with diameter of 200 nm each. The nanorods’ distribution is calculated based on the Maxwell–Garnett effective medium approach to mimic effective parabolic refractive index distribution in the fiber core. The standard stack-and-draw method was used to scale down the fiber structure and obtain subwavelength nanorods in the core. Size and distribution of individual nanorods are essential to determine modal and dispersion properties of the fiber without assistance of air holes in the fiber cladding. We study supercontinuum generation performance in this nanostructured core fiber pumping with low-cost microchip laser operating at 1550 nm with 1 ns pulse length and pulse energy of 0.4 µJ. A modulation instability-driven supercontinuum is generated in the fiber, covering a wavelength span of 1400–2300 nm. Due to possibility of dispersion engineering and all-solid structure the nanostructured fibers offer new possibilities for development of low-cost all-fiber supercontinuum light sources for the near-infrared range and cascaded ultrabroadband supercontinuum all-fiber systems.

2-μm Brillouin laser based on infrared nonlinear glass fibers.

Infrared fiber materials such as chalcogenide, tellurite, and heavily germanium-doped silica glasses are attractive materials for many applications based on nonlinear optical effects such as Kerr, Raman, and Brillouin processes. Here, we experimentally demonstrate a close-to-single-frequency Brillouin fiber laser in the 2-μm wavelength region either based on tellurite (TeO2) glass or on heavily germanium-doped silica glass. Our results reveal a strong enhancement of the Brillouin gain efficiency at 2 μm of more than 50 times that of standard silica optical fibers. A lasing threshold and narrow linewidth of 98 mW and 48 kHz, respectively, have been demonstrated in the tellurite fiber-based laser. This simple Brillouin laser source configuration confirms the potential applications of such fibers for the development of nonlinear photonic devices in the important 2-μm spectral range.

Femtosecond laser written nanostructures in Ge-doped glasses.

We report on nanostructures induced by femtosecond laser pulses in the bulk of Germanium-doped silica glasses. For studying structural properties of the nanostructure constituents small-angle x-ray scattering and SEM served to map pore size, filling factor and periodicity. Our results show that with increasing the Ge doping concentration, the aspect ratio (transverse to inscribing laser) of nanometric pores rises while they arrange in a smaller period in contrast to nanogratings in pristine fused silica. Consequently, higher optical retardance can be obtained demonstrating the pronounced glass decomposition due to the changing network structure.

Electron, hole and exciton self-trapping in germanium doped silica glass from DFT calculations with self-interaction correction

Density functional theory (DFT) calculations were employed to understand the refractive index change in germanium doped silica glasses for the trapped states of electronic excitations induced by UV irradiation. Local structure relaxation and excess electron density distribution were calculated upon self-trapping of an excess electron, hole, and exciton in germanium doped silica glass. The results show that both the trapped exciton and excess electron are highly localized on germanium ion and, to some extent, on its oxygen neighbors. Exciton self-trapping is found to lead to the formation of a Ge E′ center and a non-bridging hole center. Electron trapping changes the GeO 4 tetrahedron structure into trigonal bi-pyramid with the majority of the excess electron density located along the equatorial line. The self-trapped hole is localized on bridging oxygen ions that are not coordinated to germanium atoms that lead to elongation of the Si–O bonds and change of the Si–O–Si bond angles. We carried out a comparative study of standard DFT versus DFT with a hybrid PBE0 exchange and correlation functional. The results show that the two methods give qualitatively similar relaxed structure and charge distribution for electron and exciton trapping in germanium doped silica glass; however, only the PBE0 functional produces the self-trapped hole.

High-temperature treatment of hydrogen loaded GeO 2:SiO 2 glasses for photonic device fabrication

High-temperature treatment of hydrogen loaded silica- and germanium doped silica glass, also referred to as OH flooding, has been studied. The removal mechanism of hydroxyl groups in silica glass, during OH flooding, occurs by formation and diffusion of molecular hydrogen, while in germanium doped silica the main diffusion mechanism is attributed to diffusion of molecular water. UV exposure of OH flooded and non-treated germanium doped silica samples, from a ArF laser at 193 nm, show large changes in the asymmetric stretching vibration of Si–O–Si bridges, indicating compaction of the glass network. In addition, the thermal relaxation kinetics of the UV induced compaction are found to be similar for non-treated samples and OH flooded samples.

Light scattering in SiO2–GeO2 glasses: quantitative comparison of Rayleigh, Brillouin and Raman effects

Elastic (Rayleigh) and inelastic (Brillouin and Raman) scatterings are altogether measured in the same experimental conditions for germanium doped silica glass (5wt% GeO2). Taking into account that density and concentration fluctuations are frozen-in respectively at the fictive temperature Tf and at the chemical fictive temperature Tf′, a quantitative comparison of the different scattering processes demonstrates that the concentration fluctuations are the main reasons for the increase of the scattering. However the depolarized Rayleigh scattering is much stronger than in pure silica and also contributes to the increase of the total scattering whereas the increase of the Raman cross section due to the GeO2 introduction is much smaller.

Structural studies of germanium doped silica glasses: the role of the fictive temperature

Abstract We studied the influence of germanium atom introduction into the silica network and the influence of heat treatements on the glass structure by doing Raman and infra-red spectra of vitreous germanium doped silica (5% wt GeO 2 , 95% wt SiO 2 ). Germanium incorporates into the network by substituting Si atoms and consequently, we observed band shifts and broadening of defect peaks D 1 and D 2 . The peak positions are directly correlated with the structural state characterized by the glass fictive temperature T F of the different samples.

Ultraviolet-light-induced processes in germanium-doped silica

A model is presented for the interaction of ultraviolet (UV) light with germanium-doped silica glass. It is assumed that germanium sites work as gates for transferring the excitation energy into the silica. In the material the excitation induces forbidden transitions to two different defect states which are responsible for the observed refractive index changes. Activation energies $[1.85\ifmmode\pm\else\textpm\fi{}0.15$ eV and $1.91\ifmmode\pm\else\textpm\fi{}0.15$ eV] and rates $[(2.7\ifmmode\pm\else\textpm\fi{}1.9)\ifmmode\times\else\texttimes\fi{}{10}^{13}$ Hz and $(7.2\ifmmode\pm\else\textpm\fi{}4.5)\ifmmode\times\else\texttimes\fi{}{10}^{13}$ Hz] are determined for thermal elimination of these states. Good agreement is found with experimental results and new UV-induced effects are predicted.

One Photon and Two Photon Process in Photo-Decomposition of Germanium Oxygen Deficient Centres

UV photon-induced transformation of germanium oxygen deficient centres (GODC) in germanium-doped silica glass have been studied using photocurrent measurements, absorption and fluorescence bleaching. It has been identified that the photocurrent are generated via a two photon effect. Evidence have been found suggesting that the UV photon-induced destruction of GODCs is achieved via two reaction pathways, a single photon pathway and a two photon pathway. The process is discussed.

Photoluminescence of Bragg gratings in germanosilicatefibres excited at 488 nm

The authors have observed photoluminescence peaked near 667 nm from Bragg gratings written in germanosilicate fibres upon excitation by 488 nm radiation. The observed luminescence spectrum is consistent with the 1.9 eV spectrum owing to nonbridging oxygen hole centres in silica and germanium doped silica glasses. The strength of the luminescence appears to vary significantly depending on the fibre composition, but did not depend strongly on hydrogen content in one type of fibre studied.

Time resolved 3.10 eV luminescence in germanium-doped silica glass

In this letter we present time resolved measurements of the 3.10 eV (400 nm) photoluminescence in germainum-doped silica. The 3.10 eV band arises from a triplet to singlet transition in a GeO defect. We find that the photoluminescence decays with a time constant of around 100 μs. There is a delay roughly 10 μs in duration between excitation and the appearance of maximum photoluminescence intensity. This is evidence that an additional energy state contributes to the radiative decay of the triplet state. This state can exist within the same defect or it can exist in another defect and transfer energy to the GeO.

Ultraviolet radiation- and γ radiation-induced color centers in germanium-doped silica glass and fibers

Abstract Induced optical losses and paramagnetic Ge(n) centers were investigated in germanium-doped silica glass and optical fibers after γ and ultraviolet (UV) irradiation. It was found that both types of irradiation created similar effects. By means of selective UV irradiation, Ge (1 and 3) centers were identified in optical absorption spectra, presumably as induced bands centered at 4.4 eV and 6.2 eV, respectively. Moreover, photobleaching of Ge(1) centers took place under 266-nm wavelength excitation. In optical fibers no difference was observed between γ- and UV-induced loss spectra in the wavelength range from 480 nm to 1,900 nm. Partial reversibility of the photocoloration was observed. For comparison, the coloration effects were studied in glass prepared by means of modified chemical vapor deposition (MCVD) vapor-phase axial deposition (VAD), and plasma-activated chemical vapor deposition (PCVD) techniques.

UV and ⋎-induced paramagnetic colour centers in germanium-doped silica glass

physica status solidi (a)Volume 110, Issue 2 p. K107-K110 Short Note UV and ⋎-induced paramagnetic colour centers in germanium-doped silica glass A. N. Guryanov, A. N. Guryanov Institute of Chemistry, Academy of Sciences of the USSR, Gorkii Search for more papers by this authorE. M. Dianov, E. M. Dianov General Physics Institute, Academy of Sciences of the USSR, Moscow Search for more papers by this authorV. M. Kim, V. M. Kim General Physics Institute, Academy of Sciences of the USSR, Moscow Search for more papers by this authorV. M. Mashinskii, V. M. Mashinskii General Physics Institute, Academy of Sciences of the USSR, Moscow Search for more papers by this authorV. B. Neustruev, V. B. Neustruev General Physics Institute, Academy of Sciences of the USSR, Moscow Search for more papers by this authorV. A. Tikhomirov, V. A. Tikhomirov Institute of Nuclear Physics, Moscow State University Search for more papers by this authorV. F. Khopin, V. F. Khopin Institute of Chemistry, Academy of Sciences of the USSR, Gorkii Search for more papers by this author A. N. Guryanov, A. N. Guryanov Institute of Chemistry, Academy of Sciences of the USSR, Gorkii Search for more papers by this authorE. M. Dianov, E. M. Dianov General Physics Institute, Academy of Sciences of the USSR, Moscow Search for more papers by this authorV. M. Kim, V. M. Kim General Physics Institute, Academy of Sciences of the USSR, Moscow Search for more papers by this authorV. M. Mashinskii, V. M. Mashinskii General Physics Institute, Academy of Sciences of the USSR, Moscow Search for more papers by this authorV. B. Neustruev, V. B. Neustruev General Physics Institute, Academy of Sciences of the USSR, Moscow Search for more papers by this authorV. A. Tikhomirov, V. A. Tikhomirov Institute of Nuclear Physics, Moscow State University Search for more papers by this authorV. F. Khopin, V. F. Khopin Institute of Chemistry, Academy of Sciences of the USSR, Gorkii Search for more papers by this author First published: 16 December 1988 https://doi.org/10.1002/pssa.2211100253Citations: 3 38 Vavilov Str., SU-117942 Moscow, USSR. 49 Tropinin Str., SU-603600 Gorkii, USSR. SU-119899 Moscow, USSR. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume110, Issue216 December 1988Pages K107-K110 RelatedInformation

Radiation damage of germanium-doped silica glasses: Spectral simplification by photo- and thermal bleaching, spectral identification and microwave saturation characteristics

Germanium-doped silica glasses are important materials used in the fabrication of preforms from which optical waveguides are drawn. The preforms consist of an outer cladding of silica and an inner core of germanium-doped silica. These separate portions have been subjected to varying types of ionizing radiation and the centers generated have been studied by electron-spin resonance spectroscopy. Core samples show the generation of a single type of germanium E′ center in the silica matrix which is surrounded by three next-nearest-neighbor germanium atoms and is specified as Ge(3) after xenon lamp irradiation at room temperature. If γ irradiation is used, several germanium E′ centers with varying numbers of next-nearest-neighbor germanium atoms ranging from 0 to 3 are generated and are designated as Ge (n) centers, where n=0, 1, 2, and 3. The Ge(1) and Ge(2) centers disappear after heat treatment at a temperature of ∼500 K leaving only the Ge(3) center as the most stable of these species. The intensity of the Ge(3) centers after γ irradiation and heat treatment increases in intensity with the γ-irradiation dose to at least ∼0.5 Mrad. Photobleaching by xenon lamp irradiation of γ-irradiated core samples also decreases the intensity of the Ge(1) and Ge(2) centers. Gamma irradiation of cladding samples generates two different types of silicon E′ centers, E′α1 and Eα2. At a lower radiation dose one sees a mixture of E′α1 and Eα2, but at a higher radiation dose, E′α2 dominates. Microwave power saturation data at different temperatures on both the core and the cladding samples are used to further differentiate and characterize these various species. It is found that a relaxation mechanism involving modulation of the g anisotropy is probable.

Thermodynamic Stability and Incorporation of Phosphorus into Germanium‐Doped Silica Glass

A thermodynamic calculation of the incorporation of phosphorus into germanium‐doped silica glass is presented. The calculation predicts that, quite like germanium, the phosphorus concentration has a maximum as a function of temperature near 1800 K. In the five‐component system (CI, Ge, 0, P, Si) under typical strongly oxidizing conditions, phosphorus is lost as PO2 at equilibrium above 1800 K. A new way to minimize the Gibbs energy of the complex system is described briefly; no initial estimate of the solution components is required. This method should be widely applicable to chemical problems that involve multiple components and phases.

Pulse broadening in long-span single-mode fibers around a material-dispersion-free wavelength

Broadening of short optical pulses propagated along 10.4- and 6-km-long single-mode fibers was measured at a wavelength of 1.293 μm. The fiber core was made of germanium-doped silica glass, and the cladding was pure silica glass. The average loss was 1.33 dB/km on ten pieces about 1 km long. Measured dispersion was 3.9 psec/km/nm for 10.4-km-long fibers, which is in good agreement with the theoretical result obtained by taking the waveguide as well as material dispersion into account. The present experiment confirms that it is beneficial to use the 1.3-μm wavelength region for large-capacity digital transmission.