The mechanism of rare earth incorporation in solution doping process.
TL;DR: A model has been developed on the basis of cooperative adsorption mechanism correlating different parameters in the overall process that shows good agreement with the experimental results and can be used to predict the extent of RE incorporation for any composition if the soot layer characteristics are known.
Abstract: The mechanism involved during solution doping process has been systematically investigated by correlating the soot characteristics and solution parameters with the amount of rare earth (RE) incorporated in the core of optical fiber. Experiments show that the amount of RE incorporation may be controlled with better precision by adjusting Al ion concentration in the soaking solution. A model has been developed on the basis of cooperative adsorption mechanism correlating different parameters in the overall process. Theoretical estimation shows good agreement with the experimental results and can be used to predict the extent of RE incorporation for any composition if the soot layer characteristics are known.
Citations
More filters
TL;DR: A newly designed and fabricated ytterbium-doped large mode area fiber with an extremely low NA and related systematic investigations on fiber parameters that crucially influence the mode instability threshold are reported on.
Abstract: We report on a newly designed and fabricated ytterbium-doped large mode area fiber with an extremely low NA (~0.04) and related systematic investigations on fiber parameters that crucially influence the mode instability threshold. The fiber is used to demonstrate a narrow linewidth, continuous wave, single mode fiber laser amplifier emitting a maximum output power of 3 kW at a wavelength of 1070 nm without reaching the mode-instability threshold. A high slope efficiency of 90 %, excellent beam quality, high temporal stability, and an ASE suppression of 70 dB could be reached with a signal linewidth of only 170 pm.
101 citations
TL;DR: In this article, a simple technique is proposed to eliminate the unwanted core-clad interface defect generation and related scattering loss in rare-earth doped optical fibers containing Al-oxide, which can not be avoided without modifying fiber design or composition.
21 citations
TL;DR: It is suggested that the glass phase-separation technology shows great potential for realizing active fibers with larger core and complex fiber designs.
Abstract: We report on the preparation and optical characteristics of an Yb(3+)-doped large core silica fiber with the active core prepared from nanoporous silica rod by the glass phase-separation technology. The measurements show that the fiber has an Yb(3+) concentration of 9811 ppm by weight, a low background attenuation of 0.02 dB/m, and absorption from Yb(3+) about 5.5 dB/m at 976 nm. The laser performance presents a high slope efficiency of 72.8% for laser emission at 1071 nm and a low laser threshold of 3 W within only 2.3 m fiber length. It is suggested that the glass phase-separation technology shows great potential for realizing active fibers with larger core and complex fiber designs.
20 citations
TL;DR: In this article, the authors describe the requirements of high-power fiber lasers, such as larger fiber core/higher homogeneity and higher doping level/lower numerical number of numerical parameters.
Abstract: Recent advances in high-power fiber lasers have imposed several pairs of higher requirements on fiber materials, such as larger fiber core/higher homogeneity and higher doping level/lower numerical...
18 citations
Dissertation•
01 May 2017
TL;DR: In this article, the authors investigated the optimisation and peak power scaling of pulsed holmium-doped fiber lasers with the aim of demonstrating a fiber gain medium that is able to address the requirements of applications that currently rely on bulk crystalline Ho:YAG or Ho:YLF solutions.
Abstract: In this thesis the optimisation and peak power scaling of pulsed holmium-doped fibre lasers were investigated with the aim of demonstrating a fibre gain medium that is able to address the requirements of applications that currently rely on bulk crystalline Ho:YAG or Ho:YLF solutions. Conventional fibre processing techniques such as cleaving, end-capping and component fabrication were improved upon using CO2 laser processing. The resulting components and processes are also characterised under high power operating conditions and have enabled subsequent experimentation and demonstrations. Holmium-doped silica fibres were fabricated and characterised with the aim of reducing impurity contaminations, improving composition and achieving efficient operation at 2.1 μm. These fibres were characterised passively using transmission spectroscopy and actively in a laser configuration. The most efficient of these compositions operated with a 77% slope efficiency in a core-pumped laser up to average powers of 5 W and was then processed into a double-clad geometry. The cladding-pumped fibre was operated at 70 W output power with a slope efficiency of 67% and represents one of the highest power and most efficient cladding-pumped holmium-doped fibres demonstrated to-date. Small-signal amplifiers utilising both thulium-doped and holmium-doped silica fibres were demonstrated. These amplifiers offered a broad wavelength coverage spanning 490 nm at 15 dB gain from 1660 nm – 2150 nm. This remarkably broad wavelength coverage is attractive for a large number of disciplines looking to exploit this previously difficult-to-reach wavelength range. In addition to these devices, the average power and peak power scaling of 2 μm fibre sources was investigated. A thulium-doped fibre laser operating at 1950 nm with >170 W of output power, a tuneable holmium-doped fibre laser producing >15 W over the wavelength span from 2040 nm – 2171 nm and a pulsed holmium-doped fibre amplifier with >100 kW peak power at 2090 nm are reported. Finally we review the requirements for efficient scaling of mid-infrared optical parametric oscillators and analyse the non-linear effects that arise when attempting to scale the peak power in silica fibres in the 2 μm spectral region. We implement a range of strategies to reduce the onset of nonlinear effects and demonstrate a holmium-doped fibre amplifier with peak power levels exceeding 36 kW in a 5 ns pulse with a spectral width of
17 citations
References
More filters
TL;DR: In this paper, the effect of co-dopant oxide on the properties of SiO2 glass for a glass laser host was studied. And the effects of the Al dopant on the density and Raman spectra were also studied to obtain structural information.
Abstract: To utilize the excellent properties of silica (SiO2) glass for a glass laser host, neodymium‐aluminum (Nd–Al) and neodymium‐phosphorous (Nd–P) co‐doped SiO2 glasses were studied. They were prepared by plasma‐torch chemical vapor deposition (CVD). It was found that a doping level less than ten times the number of Nd for the Al co‐dopant and less than about fifteen times for the P co‐dopant was enough to remove undesirable fluorescence properties of Nd‐doped SiO2 glasses and make them suitable for laser application. The clustering Nd ions disperse well in a glass matrix and lasing fluorescence increases. The effects of the Al dopant on the density and Raman spectra were also studied to obtain structural information. On the basis of glass science and solution chemistry, the marked effects of both dopants were explained by the following model. Nd ions can be well incorporated into a SiO2 glass network through co‐dopant oxide forming a solvation shell around the Nd ions. This model leads to an expansible metho...
539 citations
TL;DR: In this article, the metastable binary two-liquid region is defined, and a structural interpretation of the phase separation and the effects of small oxide additions on it is offered, and evidence for both classical and possible spinodal nucleation mechanisms during liquid segregation in this system is presented.
Abstract: Metastable glass-in-glass separation was observed on rapid quenching of A12O3-SiO2 melts containing from 10 to 50 mol% A12O3. Nucleation and subsequent crystallization of mullite within the high-alumina-dispersed glass phase may occur either during cooling from the melt or on reheating. The metastable binary two-liquid region is compositionally defined, and a structural interpretation of the phase separation and the effects of small oxide additions on it is offered. Evidence for both classical and possible spinodal nucleation mechanisms during liquid segregation in this system is presented.
230 citations
TL;DR: The porous core layer deposited by modified chemical vapour deposition process has been analyzed in terms of thickness, pore size distribution, homogeneity and characteristics of the soot particles to investigate their variation with deposition temperature and input vapour composition.
Abstract: The porous core layer deposited by modified chemical vapour deposition process has been analyzed in terms of thickness, pore size distribution, homogeneity and characteristics of the soot particles to investigate their variation with deposition temperature and input vapour composition. The compositions selected were SiO2, SiO2-GeO2 and SiO2-P2O5. Rare earth ions were incorporated into the deposit by a solution doping technique. The analysis of deposited microstructures was found to provide a quantitative indication about the rare earth incorporation and its variation with respect to process conditions. Thus the characterization provides a method of controlling rare earth doping and ultimate preform/fiber properties.
78 citations
TL;DR: In this article, the upconversion process of erbium ions in ion-exchanged waveguides in a phosphate glass was studied from the pump intensity dependence of luminescence decay curves.
Abstract: The cooperative upconversion processes of erbium ions in silver film ion-exchanged waveguides in a phosphate glass were studied from the pump intensity dependence of luminescence decay curves. Cooperative upconversion coefficients of the 4I13/2 level, 7.7±0.7×10-19 and 9.3±0.7×10-19 cm3/s, were obtained for an Er3+ concentration of 1×1020 cm-3 in bulk and waveguide samples, respectively. These values are 1 order of magnitude smaller than the ones reported for silica glass. The increase in the cooperative upconversion coefficient with the increase in Er3+ concentration was found to be small. The effects of cooperative upconversion on the gain performance were analyzed for different Er3+ concentrations by a theoretical model based on experimentally measured gain with a 1.48-µm pump wavelength. Given the small cooperative upconversion coefficients in this glass, Er3+ concentrations potentially as high as 3.7×1020 cm-3 were shown to be feasible. Such high concentrations would result in a 12-dB gain at 150-mW pump power with a 4-cm-long waveguide.
74 citations
TL;DR: In this paper, the process parameters involved at various stages of solution doping method for fabricating rare earth (RE) doped optical fiber have been systematically investigated to optimize the process conditions and achieve better control over RE incorporation.
12 citations