1,721,064 research outputs found
Kinetic analysis of the new sensitization effect in the TL of silica optical fibres
No full textThe kinetic parameters of the thermoluminescence induced by X-irradiation in Ge-silica optical fibres doped with Nd, are investigated. Initially the emission spectrum consists mainly of a band near 400 nm. The combined effect, of irradiation and heating generates a new band, near 520 nm. The kinetic analysis shows that besides the broad distribution of activation energies which is typical of the amorphous silica, several monoenergetic traps are active as well. The shallower trap can be linked to the well known "110 °C peak" of quartz. It is suggested that the recombination of electrons with O2' hole centres produce the 400 nm emission while the 520 nm hand is associated with a Nd3+ hole centre. Ge4+ is assumed to be the dominant electron trap
Radioluminescence response of germanosilicate optical fibres
No full textX-ray irradiation of germanosilicate optical fibres simultaneously produces signals from both the core and substrate and so the radioluminescence spectra record the defect structure of both regions. The data provide evidence for the presence of dopants and trace impurities, as well as intrinsic defects formed by thermal and radiation processing. Examples of the changes in spectra or luminescence sensitivity with radiation dose, the influence of fibre pulling conditions and post irradiation heating are noted. The temperature dependence of the radioluminescence is reported. Whilst most of the intrinsic defects produce broad emission bands, rare earth dopants show line features. However, line features have also been noted for Al doped fibres. Such studies of fibre luminescence offer a sensitive monitor of changes in the structure of the glass network
Luminescence spectra of germanosilicate optical fibres I - radioluminescence and cathodoluminescence
No full textData are reported on the luminescence spectra generated by X-ray and electron irradiation of optical fibres, fibre preforms and silica. The impurities and imperfections in the fibre core have a higher luminescence efficiency than those in the substrate material. The core luminescence provides a major fraction of the total light emission, despite the fact that the core is a small fraction of the total fibre volume. A wide variety of overlapping emission bands are reported. The spectra are strongly temperature dependent but the component emission bands can generally be linked to either Ge impurities, giving the 400 nm band, exciton emission near 460 nm or other blue/UV bands linked to E'-type defects. Overall, the study of the fibre luminescence provides a sensitive technique for analysis d changes and repeatability of fibre fabrication
The effect of thermal annealing on luminescence centres in Ge-silica fibres
No full textThe radioluminescence spectrum of Ge-silica fibres doped with Nd is found to change by the effect of pre-irradiation and thermal annealing. Originally the spectrum consists of a gaussian band centred near 3.1 eV (400 nm). Following the irradiation and heating an additional asymmetric band appears near 2.4 eV (520 nm). On top of this band there is a line spectrum, which can be ascribed to internal transitions of the Nd3+. On the basis of the spectroscopic data and previous results of thermoluminescence measurements, a model is suggested for the luminescence and the effect of the thermal annealing. The blue and green bands are ascribed to an O2' molecular ion and a hole centre near the Nd3+ ion, respectively.<br/
Very low loss ion implanted planar waveguides in lead germanate glass
No full textIon implantation has been used to produce very low loss optical waveguides in lead germanate glass samples. Then is an increase in the refractive index of 0.35% for the given ion beam parameters. The loss can be as low as 0.15 dB/cm after thermal annealing
An optical fibre rereadable radiation dosimeter for use at high doses and at elevated temperature
Full text linkA new type of radiation dosimeter for large radiation doses is described, which is based on silica fibre material. Conventional radioluminescence or thermoluminescence of silica produces emission in the blue region of the spectrum. However, in this new material irradiation, in conjunction with a heat treatment, generates a green emission band. The intensity of the green band can be monitored by either radioluminescence or thermoluminescence using a test dose. The signals are directly related to the total irradiation history of the material. The dosimeter is therefore rereadable. The production mechanism of the green emission centre requires a thermal processing stage, with an activation energy of 0.52 eV. Further, the dosimeter is effective at recording radiation during high-temperature exposure, to at least 400°C, with the subsequent dosimetry being performed below 200°C
Thermoluminescence evidence for laser-induced crystallisation of Tm<sup>3+</sup>-doped germanosilicate fibers
No full textLaser illumination of optical fibres can modify the refractive index of germano-silicate fibres and introduce optical non-linearity. New luminescence data not only confirm that the laser treatments are wavelength specific, but also the defect structures are altered. Low temperature thermoluminescence of fibres, previously illuminated at 476 nm, gives a glow peak of <2 K width, which is interpreted as evidence of a transition between laser induced crystalline phases. <br/
Ion-implanted lanthanum fluoride waveguides
No full textThe effects of He+ and H+ implantation into LaF3 substrates have been investigated at both room temperature and 77 K. At room temperature the surface of the samples becomes black, possibly due to chemical reduction effects, but at low temperature the crystals remain clear and a refractive index change is observed which produces a surface waveguide. The dark mode spectra of these guides have been recorded using the prism coupling technique, and their refractive index profiles have been deduced from the spacing of these modes. The ion implantation produces a thin optical barrier layer of low refractive index at the end of the ion range. This paper discusses the use of multiple-energy implantation to produce a broad optical barrier in order to reduce the tunnelling losses of the guides, and subsequent thermal annealing to reduce absorption and scattering losses caused by colour centre formation in the electronic stopping surface region of the guides. It is concluded that either single- or multiple-energy He+ implants can be ideally used to form waveguides, for applications in the blue/UV or red/IR wavelength regions, respectively, with losses of a few dB/cm
Ion-implanted Nd:GGG channel waveguide laser
Full text linkWe report what is to our knowledge the first fabrication and laser operation of ion-implanted Nd:GGG channel waveguides. Diode-pumped operation has been achieved with absorbed power thresholds as low as ~2 mW and a slope efficiency of ~30% with respect to absorbed power
BaTiO<sub>3</sub> waveguide self-pumped phase conjugator
No full textFor the first time to our knowledge, self-pumped phase conjugation is reported in a planar waveguide structure in a BaTiO3 single crystal. The waveguide was fabricated by the technique of ion implantation, with 1.5-MeV H+ ions at a dose of 1016 ions/cm2. Phase-conjugate reflectivities >20% have been measured for waveguide self-pumped phase conjugation, and, for a given input power, an order-of-magnitude reduction in the response time is observed in the waveguide compared with the bulk. The fidelity of phase conjugation in the guide is also discussed
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