Showing papers by "Alexander J. Boyland published in 2010"

MCVD in-situ solution doping process for the fabrication of complex design large core rare-earth doped fibers

Abstract: We report on the fabrication and characterization of rare-earth doped silica fibers manufactured using an in-situ solution doping technique, which is compatible with conventional modified chemical vapor deposition equipment. The in-situ technique permits significantly more doped layers to be deposited, compared to conventional solution doping, and is directly applicable for the fabrication of large core rare-earth doped fibers suitable for high-power fiber sources. Ytterbium-doped aluminosilicate fibers fabricated using the new in-situ doping technique are reported and the results are compared to fibers fabricated using a conventional solution doping method.

Multi-watts narrow-linewidth all fiber Yb-doped laser operating at 1179 nm

Abstract: An all-fiber, narrow-linewidth, high power Yb-doped silica fiber laser at 1179 nm has been demonstrated. More than 12 W output power has been obtained, corresponding to a slope efficiency of 43% with respect to launched pump power, by core-pumping at 1090 nm. In order to increase the pump absorption, the Yb-doped fiber was heated up to 125°C. At the maximum output power, the suppression of amplified spontaneous emission was more than 50 dB. Furthermore, theoretical work confirms that the proposed laser architecture can be easily scaled to higher power.

Wideband EDFA Based on Erbium Doped Crystalline Zirconia Yttria Alumino Silicate Fiber

Abstract: A wideband erbium-doped fiber amplifier (EDFA) is demonstrated using an Erbium-doped zirconia fiber as the gain medium. With a combination of both Zr and Al, we could achieve a high erbium doping concentration of 4320 ppm in the glass host without any phase separations of rare-earths. The Erbium doped fiber (EDF) is obtained from a fiber preform, which is fabricated in a ternary glass host, zirconia-yttria-aluminum codoped silica fiber using a MCVD process. Doping of Er2O3 into Zirconia yttria-aluminosilicate based glass is done through solution doping process. The maximum gain of 21.8 dB is obtained at 1560 nm with 2 m long of EDF and co-pumped with 1480 nm laser diode. At high input signal of -4 dBm, a flat-gain at average value of 8.6 dB is obtained with a gain variation of less than 4.4 dB within the wavelength region of 1535-1605 nm and using 3 m of EDF and 100 mW pump power. The corresponding noise figure is maintained below 9.6 dB at this wavelength region.

Performance comparison of Zr-based and Bi-based erbium-doped fiber amplifiers.

Abstract: In this Letter, we present a comprehensive comparison of the performance of a zirconia-based erbium-doped fiber amplifier (Zr-EDFA) and a bismuth-based erbium-doped fiber amplifier (Bi-EDFA). The experimental results reveal that a Zr-EDFA can achieve comparable performance to the conventional Bi-EDFA for C-band and L-band operations. With a combination of both Zr and Al, we could achieve a high erbium-doping concentration of about 2800 ppm (parts per million) in the glass host without any phase separations of rare earths. The Zr-based erbium-doped fiber (Zr-EDF) was fabricated using in a ternary glass host, zirconia-yttria-aluminum codoped silica fiber through a solution-doping technique along with modified chemical vapor deposition. At a high input signal of 0 dBm, a flat gain at average value of 13 dB is obtained with a gain variation of less than 2 dB within the wavelength region of 1530-1575 nm and using 2 m of Zr-EDF and 120 mW pump power. The noise figures are less than 9.2 at this wavelength region. It was found that a Zr-EDFA can achieve even better flat-gain value and bandwidth as well as lower noise figure than the conventional Bi-EDFA. (C) 2010 Optical Society of America

Yb2O3-doped YAG nano-crystallites in silica-based core glass matrix of optical fiber preform

Abstract: Yb2O3-doped yttrium aluminium garnet (YAG) nano-crystals within the silicate glass-based optical fiber preforms were obtained through the conventional-modified chemical vapour deposition (MCVD) and solution doping technique. Nano-crystals were developed with soaking of the porous phospho-silica or pure silica core layer in a solution containing the ytterbium, yttrium and other co-dopants, including fluorine using 10–15% fluorosilicic acid, and through post-annealing of the preform at a temperature of around 1450 °C. The size, shape and nature of Yb2O3-doped phase-separated nano-crystallites were evaluated from HRTEM images along with the electron diffraction pattern based on the doping levels of phosphorous and fluorine. The size of nano-crystallites was maintained within 6–10 nm when doped with 0.25 mole% of fluorine. X-ray analyses EDX data reveals that the nano-particles are rich in Yb:YAG, and uniformly dispersed into the amorphous silica glass matrix. The novelty of this technique involves the direct synthesis of rare-earth doped phase-separated nano-crystallites within the core region of silica glass preforms. This class of fibers containing the nano-particles with or without Yb:YAG crystalline nature will keep the advantage of the mechanical properties as well as good lasing properties under high power application compared to the Yb:YAG ceramic laser.

Measurement of photodarkening in Yb-doped aluminosilicate fibres at elevated temperature

Abstract: Photodarkening behaviour in Yb-doped aluminosilicate fibres at elevated temperatures is reported. The fibre was core-pumped at 977 nm and the transmitted powers were monitored at 633 (probe) and 977 nm (pump) simultaneously with ~47% of population inversion of Yb3+ ions. A saturated photodarkening loss was found, which is inversely proportional to temperature and, at ~573 K, the loss was negligible at the pump wavelength. From the decay curves at different temperatures, it was found that the photodarkening involves second-order kinetics to form colour centres.

Rare-earth doped optical fiber fabrication using novel gas phase deposition technique

Abstract: We report a highly versatile gas phase technique for making ytterbium doped silica fibers. Initial results generated 200W output power with a slope efficiency of 72%.

Ytterbium-doped low-NA P-Al-silicate large-mode-area fiber for high power applications

Abstract: We demonstrate an efficient, ytterbium-doped low-NA fiber with core glass containing high levels of Al 2 O 3 and P 2 O 5 in silica host that shows low-photodarkening and generated 175 W of continuous-wave output power with 80% laser efficiency.

In-situ solution doping technique for novel geometry rare-earth doped fiber fabrication

Abstract: We report on the fabrication and characterization of an YDFL with a pedestal geometry fabricated using an in-situ solution doping process. The fiber has a unique non-stressed inner-cladding and exhibits good efficiency.

Ytterbium doped nano-crystalline optical fiber for reduced photodarkening

Abstract: We report suppression of photodarkening in Yb-doped nano-crystalline fibers in silica host. The photodarkening induced loss reduced by 20 times compared to Yb-doped aluminosilicate fibers. The laser efficiency of the nano-crystalline fiber was 79%.

Beam quality and spectral evolution in large-core cladding-pumped cascaded-Raman fiber converter

Abstract: We fabricate the first large-core double-clad Raman fiber and use it for efficient pulsed cladding-pumped fiber Raman amplification. The beam-quality of the output beam improves to diffraction-limited through cascaded Raman scattering.

Multi-wavelength fiber laser with erbium doped zirconia fiber and semiconductor optical amplifier

Abstract: Multi-wavelength hybrid fiber lasers are demonstrated in both ring and linear cavities using a fabricated Erbium-doped Zirconia fiber (EDZF) and semiconductor optical amplifier (SOA) as gain media. In both configurations, the a fiber loop mirror, which is constructed using a 3 m long polarization maintaining fiber (PMF) and a polarization insensitive 3dB coupler is used as a comb filter for the fiber laser. In the ring cavity, 10 simultaneous lines with peak power above -26 dBm is obtained at 1550 nm region. This is an improvement compared to the linear cavity configuration which has only 5 simultaneous lines observed from wavelength 1556.1 nm to 1563.0 nm with the peak power above -40 dBm. Both hybrid lasers has a constant line spacing of 1.7 nm, which is suitable for wavelength division multiplexing and sensing applications and shows a stable operation at room temperature.

Novel fiber fabrication methods benefit fiber lasers

Abstract: New modified chemical vapor deposition (MCVD)-based in-situ solution doping and chelate-in-crucible deposition techniques are improving the optical fibers from which fiber lasers are manufactured.

Novel fibre technology for high-power lasers

Abstract: We review and discuss the recent advances in high-power fibre lasers with a particular focus on novel fibre technology, which includes conventional double-clad, large-core fibres for continuous-wave generation, double-clad passive-core fibres for Raman conversion, microstructured fibres for four-wave mixing, all-solid photonic bandgap fibres for waveguide filtering, etc.