Ytterbium- and chromium-doped fibre laser: from chaotic self-pulsing to passive Q-switching

A spontaneously chaotic, self-pulsing ytterbium-doped fibre laser is partially stabilized into the passively Q-switched mode of operation using a chromium-doped saturable absorber fibre. This original all-fibre laser produces sustained and stable trains of smooth pulses at high repetition rate.Comment: 1 page abstract; at 20th International laser physics workshop, Sarajevo : Bosnia And Herzegovina (2011

Erbium-doped nanoparticles in silica-based optical fibres

Developing of new rare-earth (RE)-doped optical fibres for power amplifiers and lasers requires continuous improvements in the fibre spectroscopic properties (like shape and width of the gain curve, optical quantum efficiency, resistance to spectral hole burning and photodarkening...). Silica glass as a host material for fibres has proved to be very attractive. However, some potential applications of RE-doped fibres suffer from limitations in terms of spectroscopic properties resulting from clustering or inappropriate local environment when doped into silica. To this aim, we present a new route to modify some spectroscopic properties of RE ions in silica-based fibres based on the incorporation of erbium ions in amorphous dielectric nanoparticles, grown in-situ in fibre preforms. By adding alkaline earth elements, in low concentration into silica, one can obtain a glass with an immiscibility gap. Then, phase separation occurs under an appropriate heat treatment. We investigated the role of three alkaline-earth elements: magnesium, calcium and strontium. We present the achieved stabilisation of nanometric erbium-doped dielectric nanoparticles within the core of silica fibres. We present the nanoparticle dimensional characterisation in fibre samples. We also show the spectroscopic characterisation of erbium in preform and fibre samples with different compositions. This new route could have important potentials in improving RE-doped fibre amplifiers and laser sources.Comment: arXiv admin note: text overlap with arXiv:1201.111

Er doped oxide nanoparticles in silica based optical fibres

Erbium doped materials are of great interest in optical telecommunications due to the Er3+ intra-4f emission at 1.54 ?m. Erbium doped fibre amplifiers (EDFA) were developed in silica glass because of the low losses at this wavelength and the reliability of this glass. Developments of new rare earth doped fibre amplifiers aim to control their spectroscopic properties including shape and width of the gain curve and optical quantum efficiency. Standard silica glass modifiers, such as aluminium, result in very good properties in current EDFA. However, for more drastic spectroscopic changes, more important modifications of the rare earth ions local environment are required. To address this aim, we present a fibre fabrication route creating rare earth doped calcia?silica or calcia?phosphosilica nanoparticles embedded in silica glass. By adding alkaline earth elements such as calcium, in low concentration, one can obtain a glass with an immisci- bility gap so that phase separation occurs with an appropriate heat treatment. We investigated the role of two elements: calcium and phosphorus (a standard silica modifier). Scanning electron microscopy shows that nanoparticles are only observed when calcium is incorporated. The size of the particles is determined to be around 50 nm in preform samples. The nature of these particles depends on phosphorus content: without P, electron diffraction shows that the particles are amorphous whilst they are partially crystalline when phosphorus is added. In addition through use of energy dispersive x-ray techniques, we have shown that erbium ions are located in the nanoparticles

Luminescent Ions in Silica-Based Optical Fibers

We present some of our research activities dedicated to doped silica-based optical fibers, aiming at understanding the spectral properties of luminescent ions, such as rare-earth and transition metal elements. The influence of the local environment on dopants is extensively studied: energy transfer mechanisms between rare-earth ions, control of the valence state of chromium ions, effect of the local phonon energy on thulium ions emission efficiency, and broadening of erbium ions emission induced by oxide nanoparticles. Knowledge of these effects is essential for photonics applications

Tailoring of the luminescent ions local environment in optical fibers, and applications

The chapter is situated in the fields of fiber materials sciences and technologies (particularly dealing with the fiber glass compositions and luminescent ion doping, and transparent glass ceramic optical fibers), and applications such as fiber lasers and amplifiers. We propose to present a review of research activities on rare-earth (RE) and transition metals (TM) doped silica-based optical fibers, aiming at understanding theier spectral properties, and particularly some of their optical transitions that will allow interesting and alternative applications. Silica, as opposed to alternative, low temperature materials, is chosen for practical and economical reasons. Selected RE and TM ions are studied both as probes of their local environment and for their application potentials. In this chapter, we will focus on erbium (Er) ions for the potential spectral 'tailoring' of its gain curve at 1.55 $\mu$m, thulium (Tm) as local environment probe along both near infrared transitions around 0.8 and 1.47 $\mu$m, and chromium (Cr) for the sensitivity of valency and spectroscopy to the glass composition and its potential as saturable absorber in lasers. We will present some extensive studies on the influence of the local environment on dopants: such as (but not limited to) energy transfer mechanisms between rare-earth ions of same nature (Tm-Tm) or different nature (Yb-Tm), effect of the local phonon energy on Tm ions emission efficiency, broadening of Er ions emission induced by oxide nanoparticles grown in situ during the fabrication process, etc. Knowledge of these effects is essential for photonics applications, and many studies are under progress or are still needed in this field. The potential of some applications which could benefit from the basic studies on materials are also numerically studied : 0.8-$\mu$m thulium-doped fiber laser, so-called S-band (1.47 $\mu$m) thulium-doped amplifier for telecommunications and laser applications, sensitisation of Tm-based devices using ytterbium sensitized ions.Comment: arXiv admin note: substantial text overlap with arXiv:0911.168

PASSIVELY Q-SWITCHED YTTERBIUM AND CHROMIUM ALL-FIBRE LASER

A chromium-doped saturable absorber fibre stabilizes an otherwise spontaneously chaotic ytterbium- doped fibre laser. This original passively Q-switched all-fibre laser produces sustained and stable trains of smooth pulses at high repetition rate