1 Watt Er/Yb singlemode superfluorescent optical fibre source

A singlemode superfluorescent Er/Yb optical fibre source is described, capable of generating >1 W of output power. The spectral bandwidth of the source can be varied between 0.5 and 4 nm by filtering     

1 W single-transverse-mode Yb-doped double-clad fibre laser at 978nm

A novel all-glass Yb-doped double-clad fibre laser that emits over 1 W of single-transverse-mode output at 978 nm is described. This device is efficiently pumped with 2.5 W of launched power from a single 200 μm broad-area laser diode at 915 nm     

La2O3-Al2O3-SiO2 Glasses for High-Power, Yb3+-Doped, 980-nm Fiber Lasers

Single-mode semiconductor pumps have failed to keep pace with the increasing power requirements of Er-doped fiber amplifiers (EDFAs), so there is a need for high-powered 980-nm sources. Yb³⁺-doped tapered fiber lasers can provide high-power output by conversion of a low-brightness, high-powered, 920-nm, multimode broad stripe laser diode to a high-brightness, 980-nm, single-mode output. The tapered fiber laser requires a fiber with high numerical aperture (NA) (>0.4), a rectangular core, and good Yb³⁺ spectroscopy for efficient operation. CVD-based fiber fabrication methods are incapable of delivering fibers with an NA > ∼0.3 or with good efficiency at 980 nm so a new method of high-NA fiber fabrication was developed. The core glass composition is critical for maintaining a high-NA fiber with good power extraction while avoiding phase separation, loss, and clustering. The SiO₂ level controlled the NA and interdiffusion between core and clad, while the Al₂O₃/La₂O₃ ratio controlled phase separation. A La₂O₃-Al₂O₃-SiO₂ glass was developed that is compatible with a pure SiO₂ cladding glass and has a laser slope efficiency of 70% at 980 nm. The optimized fiber composition yielded 450 mW of 980-nm power in a single-mode fiber.     

Nd/sup 3+/-doped single mode fibre superfluorescent source with 320 mW output power

A diode array pumped Nd/sup 3+/-doped superfluorescent fibre source with 320 mW output power and a 4.6 nm FWHM bandwidth centred at 1058 mu m is reported. The device is prevented from lasing off reflected light from Rayleigh backscatter by seeding an Nd/sup 3+/-doped fibre amplifier with a primary superfluorescent source of moderate power.<>     

Diode-array pumping of Er3+/Yb3+ Co-dopedfiber lasers and amplifiers

Single-mode double-clad Er³⁺/Yb³⁺ co-doped fibers are shown to be suitable for diode array pumping at around 960 nm. A fiber laser with 96-W output power at 1.53 μm and a power amplifier exhibiting a small signal gain of 24 dB and a saturated output power of +17 dBm are reported     

Fabrication and characterization of Yb3+:Er3+phosphosilicate fibers for lasers

Fabrication process of efficient Yb³⁺,Er³⁺ codoped phosphosilicate fibers by modified chemical vapor deposition (MCVD) combined with the solution doping technique is studied in detail. We show that the process can be adapted to incorporate low viscosity phosphate glass and some important issues in the fabrication process are discussed. These include the sensitive presintering pass. We also report on the fabrication of a low loss all-glass double clad Yb³⁺:Er³⁺ codoped fiber. We explain how we evaluate the fibers and discuss the effect of the ytterbium to erbium concentration ratio on the laser characteristics. Finally, we present results of some investigations into the mechanisms which can affect the efficiency of the lasers, and show that the detrimental up-conversion from the metastable level of the erbium ions is dramatically reduced by the presence of the ytterbium ions     

Wavelength combining fused-taper couplers with low sensitivity to polarisation for use with 1480 nm-pumped erbium-doped fibre amplifiers

Fused-taper wavelength division multiplexing (WDM) couplers for use in combining the 1480 nm pump wavelength with the 1540 nm signal wavelength of erbium-doped fibre amplifier systems are reported. Output port isolation in excess of 15 dB has been achieved at the centre of each channel with very low polarisation sensitivity of <0.2 dB over a 30 nm range about the channel centres.<>     

Role of Aluminum in Ytterbium–Erbium Codoped Phosphoaluminosilicate Optical Fibers

We report on a series of ytterbium–erbium codoped aluminophosphosilicate fibres fabricated by the modified chemical vapor deposition and solution doping technique where the concentration of aluminum is gradually increased in the region [A1]<[P]. We observe from deflection measurements that with increasing aluminum content the refractive index decreases and the phase separation increases. Laser slope efficiencies decrease when the aluminum concentration approaches the phosphorus concentration and the trend is seen to be correlated with the reduction in energy transfer rate when the aluminum concentration is increased. Raman spectra show the reduction of the highest phonon energy peak when the aluminum content is increased. The erbium⁴I_13/2→⁴I_15/2transition fluorescence spectrum and the lifetime of the erbium⁴S_3/2level show little change from the pure phosphosilicate host for the whole range of aluminum concentrations tested. The results are explained in term of formation of AlPO₄structural units.     

Twincore erbium-doped fibre amplifier with passive spectral gain equalisation

Automatic spectral gain equalisation is demonstrated using controlled spatial hole-burning in an erbium-doped twincore fibre. Gain equalisation rates up to 0.11 dB difference between input signal levels are demonstrated and should increase the useful bandwidth of cascaded amplifiers.<>     

Broad-band diode-pumped ytterbium-doped fiber amplifier with 34-dBmoutput power

We investigate a high-power diode-pumped double-clad ytterbium-doped fiber amplifier with 34-dBm average output power and 1050-1095-nm bandwidth. A multidiode concentrator pumps the amplifier at 980 nm, with ~6 W of power launched into the inner cladding. Besides CW-signals, we amplify pulses from a mode-locked laser to 1 kW of peak power with only minor nonlinear distortions as well as pulses from a Q-switched laser to 50 μJ of energy. Reflections and backscatter limit the gain of the amplifier to 40 dB for a pump power of 2.5 W. For higher pump-powers than this, the amplifier started to self-Q-switch. The results are important for the development of cladding-pumped high-power fiber amplifiers