High-gain Fiber Amplifier Research Articles

Efficient structural manipulation of PbS in Er-doped silica optical fibers for enhanced amplification systems

In active silica optical fibers, improving the solubility and uniformity of non-concentration-quenching luminescence centers is a key strategy to achieve high gain fiber amplifiers. Herein, we report a novel Er-doped silica optical fiber (EDF) modified by PbS semiconductor incorporation for the first time. Owing to the bridge role of PbS, Er2O3 nanofilms deposited on the substrate via atomic layer deposition (ALD) have porous and loosely layered network structures with an increasing number of ALD-PbS layers. Subsequently, during the high-temperature fiber preparation process, this loose porous structure aids the dissolution and provides an optimal local environment of Er3+ ions in the silica matrix. As a result, the maximum phonon energy of the silica network for PbS/Er co-doped silica optical fiber (PEDF) is reduced, resulting in an increase of the Er3+ ion fluorescence lifetime, approximately 11.455 ms. Furthermore, we achieved 34 dB maximum gain of PEDF sample with the lowest noise figure of 3.9 dB at 1.5 μm. The gain bandwidth over 20 dB of PEDF is approximately 46 nm, which is nearly 44% higher than that of EDF. These results indicate that the PEDF prepared by structural manipulation has great potentials in optical fiber amplifier and laser applications.

High-efficiency, high-gain, all-fibered double-pass configuration for low-duty-cycle temporally shaped nanosecond pulse amplification

Abstract A high-gain fiber amplifier at 1053 nm with a double-pass configuration is proposed. Compared to the Faraday-based double-pass structures, the pump efficiency is almost doubled, and the optical signal-to-noise ratio is improved as well. The effects of fiber length and the insertion loss of elements between two passes on the efficiency are studied experimentally, which is meaningful for the optimization of double-pass amplifiers. Using the fibered polarized beam splitters allow for the orthogonal propagation of forward and the backward signals on the same polarization-maintaining fiber, the polarization mode dispersion in the amplifier is hence totally avoided. With this structure, over 50-dB gain is obtained at pump power of 800 mW for a 1053-nm, 1-Hz nanosecond pulse.

Transverse-Mode Instability in High-Gain Few-Mode Yb3+-Doped Fiber Amplifiers With a 10-μm Core Diameter With or Without Backward Reflection

Spatio-temporal transverse instability of the fundamental mode in high-gain fiber amplifiers based on a highly Yb 3+-doped few-mode polarization maintaining fiber with a core diameter of 10 μm was studied. Both experimental and theoretical analyses revealed the nonlinear power transformation of the ${\rm{LP}}_{01}$ fundamental mode into high-order modes. Numerical simulation showed a self-consistent growth of the higher order mode and traveling refractive index grating accompanying the population grating induced by the mode interference field (due to different polarizability of the excited and unexcited ${\rm{Yb}}^{3+ }$ ions). The threshold power for the transverse-mode instability was observed to change from a fraction of a Watt to tens of Watts depending on the fiber core diameter, numerical aperture, dopant concentration, power of the input signal, and the signal bandwidth. The threshold was registered to decrease dramatically in the presence of a backward reflection of the signal from the output fiber end. Numerical simulation revealed that the presence of the backward-propagating wave resulted in four-wave mixing on the common long-period index grating induced by the interference field of mode pairs. The dynamic of the instability threshold variation and a specific case of larger core fiber characterized by competition of the electronic and temperature index gratings is discussed.

Enhanced 1.32 μm fluorescence and broadband amplifying for O-band optical amplifier in Nd3+-doped tellurite glass

WO3 oxides with relatively high phonon energy and different concentrations were introduced into the Nd3+-doped tellurite-based glasses of TeO2-ZnO-Na2O to improve the 1.32 μm band fluorescence emission. The absorption spectra, Raman spectra, 1.32 μm band fluorescence spectra and differential scanning calorimeter (DSC) curves were measured, together with the Judd-Ofelt intensity parameters, stimulated emission and gain parameters were calculated to evaluate the effects of WO3 amount on the glass structure and spectroscopic properties of 1.32 μm band fluorescence. It is shown that the introduction of an appropriate amount of WO3 oxide can effectively improve the 1.32 μm band fluorescence intensity through the enhanced multi-phonon relaxation (MPR) processes between the excited levels of Nd3+. The results indicate that the prepared Nd3+-doped tellurite glass with an appropriate amount of WO3 oxide is a potential gain medium applied for the O-band broad and high-gain fiber amplifier.

Er(3)/Yb(3)-codoped phosphate glass for short-length high-gain fiber lasers and amplifiers.

Er(3)/Yb(3)-codoped phosphate glass with compositions of (78.2-x)P(2)O(5)-14Al(2)O(3)-5Li(2)O-1K(2)O-1.8Yb(2)O(3)-xEr(2)O(3)(x=0.2,0.4,0.6) in mol. % were investigated. Judd-Ofelt (JO) intensity parameters have been calculated to predict radiative properties based on absorption spectra. The stimulated emission cross section (σ(e)) calculated according to McCumber theory was 1.50×10(-20) cm(2), almost twice larger than values reported before. The effective line width (Δ(eff)), full width at half-maximum (FWHM) and the quality parameters for designing optical amplifier devices were listed in the table compared with other types of phosphate glass matrices. A theoretical model of a Er(3)/Yb(3)-codoped system based on rate and power propagation equations was put forward to investigate the potential advantages of the materials applied for short-length, high-gain fiber amplifiers. A simulated gain of 32.2 and 2.6 dB/cm per unit length was achieved in 12.5-cm-long fiber.

Heavily Tm3+-Doped Silicate Fiber for High-Gain Fiber Amplifiers

We report on investigation the potential of a 7 wt% (8.35 × 1020 Tm3+/cm3) doped silicate fibers for high-gain fiber amplifiers. Such a high ion concentration significantly reduces the required fiber length of high-power 2 μm fiber laser systems and allows the high-repetition rate operation in 2 μm mode-locked fiber lasers. To evaluate the feasibility of extracting high gain-per-unit-length from this gain medium, we measure several key material properties of the silicate fiber, including the absorption/emission cross-sections, upper-state lifetime, fiber background loss, and photodarkening resistance. We show through numerical simulations that a signal gain-per-unit-length of 3.78 dB/cm at 1950 nm can be achieved in a watt-level core-pumped Tm3+-doped silicate fiber amplifier. In addition, an 18-dB 2013-nm amplifier is demonstrated in a 50-cm 7 wt% Tm3+-doped double-clad silicate fiber. Finally, we experimentally confirm that the reported silicate host exhibits no observable photodarkening.

Optical pumping in ^4He with frequency-shifted feedback amplification of light

We use a frequency-shifted feedback technique with a high-gain fiber amplifier operating at λ=1083 nm to produce a multifrequency light beam that covers a controllable spectral range. It is ideal for optically pumping a gas of metastable He because it spans the Doppler width, and its high efficiency has implications for many applications. Measurements confirm that eight times fewer atoms are left in the unchosen states with multifrequency light.

Low-loss fusion splicing of erbium-doped optical fibers for high performance fiber amplifiers

An optimization process is described for reducing the fusion splice loss between Er-doped and standard single mode fibers, which differ significantly from each other in their physical and optical properties. As a result of this process, an average splice loss of 0.11 dB at 1300 nm in such fiber pairs has been achieved. The experimental splice loss data approached the theoretically predicted values. High-gain fiber amplifier experiments using the low-loss splicers obtained in the Er-doped and standard fiber combination are also discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>