Doped ZBLAN Fiber Amplifier Research Articles

Dual-wavelength single-frequency Tm:ZBLAN fiber amplifier operating at 1.94 and 2.33 μm

We report here, to the best of our knowledge, the first dual-wavelength single-frequency thulium-doped fiber amplifier operating at 1.94 and 2.33 μm. The single-stage, Tm3+-doped ZBLAN fiber amplifier, ground-state pumped by a 793-nm laser diode, yielded a stable output power of 1.45 W at 2332 nm and 7.4 W at 1939 nm. The injection of 1.94-μm seed effectively suppresses parasitic lasing in the 2.33-μm Tm fiber amplifier. The experiment investigated the competitive relationship between the 2-μm transition and the 2.3-μm transition, and the results suggest that the injection of 1.94-μm seeds is beneficial to the improvement of 2.33-μm efficiency, while the injection of 2.33-μm seed slightly reduces the 1.94-μm efficiency.

High-gain single-frequency Tm3+-doped ZBLAN fiber amplifier at 2.33 μm.

We report here, to the best of our knowledge, the first high-gain, single-frequency Tm3+-doped fiber amplifier operating at the 2.3-μm band with conventional ground-state pumping transition (3H6→3H4) at 793 nm. The gain fiber is an 8.5-m-long ZBLAN fiber with a Tm3+ doping concentration of 3 mol.%, and the seed is a single-frequency distributed feedback diode laser operated at 2331.9 nm. A gain up to 24.1 dB is generated for ∼14 W of launched pump power with the maximum output power of 246 mW. The competitive 3F4 →3H6 laser transition at ∼2 µm is also investigated, and the prospects for further power scaling are discussed.

High-power 813-nm Tm3+-doped ZBLAN fiber MOPA with signal-light photodarkening suppression.

The photodarkening suppression effect of an 813-nm Tm3+-doped ZBLAN fiber amplifier has been investigated. We have experimentally observed that a photodarkened fiber can be bleached by an 813-nm light and that the photoinduced loss during the amplifier operation is effectively suppressed with the help of the high-power signal. To the best of our knowledge, this is the first investigation of the photodarkening suppression by using a higher power signal in Tm3+-doped fiber amplifiers. Based on these signal photodarkening suppression effects, we have designed a multistage fiber amplifier, and demonstrated the stable operation of the 1.15-W fiber master oscillator power amplifier at 813 nm without additional photobleaching light.

Experimental and Numerical Investigations on Q-Switched Laser-Seeded Fiber MOPA at 2.8 μm

An Er <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped ZBLAN fiber amplifier for Q-switched pulses at 2.79 μm is reported. Over 24 μJ of pulse energy at an average output power of 1.0 W was achieved at a maximum available pump power of 9.4 W. The efficiency of this pulsed laser fiber amplifier is about 10%. Our simulation predicts that over 300-μJ pulses can be achieved with this fiber amplifier when a 120-W pump is used.

Noise figure and gain temperature dependent of praseodymium-doped fiber amplifier by using rate equations

A theoretical study of the temperature dependent noise effects of praseodymium-doped fiber amplifiers (PEDFAs) has been examined. The Pr 3+-doped ZBLAN fiber amplifier pumped at 1017 nm and Pr 3+-doped GeGa-sulfied fiber amplifier pumped at 1028 nm are chosen. The temperature-dependent rate and propagation equation related to four-level system consideration which is based on the population difference among amplification levels has been used. The population difference depends on pump and signal powers, Boltzman factor K B , cross-sections, noise figure (NF) and Pr 3+ concentration. The numerical results obtained over the temperature range from −20 °C to + 60 °C are used to present an analytical expression for the signal gain and noise figure effects in PDFAs length and noise figure with input pump power. The amplified spontaneous emission (ASE) has been taken into account.

Modelling consideration of praseodymium-doped fiber amplifiers for 1.3 μm wavelength applications

To obtain the temperature-sensitive rate equations, a new energy level diagram of Praseodymium ion (Pr3+) in a glass host is modelled. By solving the modified rate equations, an analytical expression is presented to investigate the temperature dependence of the signal gain of a praseodymium-doped fiber amplifier (PDFA). It is seen that a change in the signal gain slightly depends on the variation of the distribution of Pr3+-ions in transitions 3F4↔3F3 with the temperature. Numerical calculations are carried out for the temperature range which is changing from −20 to +60°C. Pr3+-doped ZBLAN fiber amplifier pumped at 1017nm and Pr3+-doped sulfide fiber amplifier pumped at 1028nm are selected as an application for the 1.3μm signal wavelengths. It is also seen that the prediction of the model is in good agrement with their experimental results.

Optimisation of a two colour pumped Tm3+-doped ZBLAN fibre amplifier at 1.49 µm

The authors have constructed a 4 metre length thulium-doped ZBLAN fibre amplifier optically pumped at 0.8 µm by a tuneable Ti∶Sapphire and at 1.06 µm by an Nd3+∶YAG laser. The authors obtained 12.5 dB for small-signal gain at 60 mW for the two pumps' optical power. The behaviour of the amplifier has been analysed with the optical power of the signal approaching the saturation condition (−5 dBm) and at different wavelengths for the Ti∶Sapphire pump laser. A model was developed for the optimisation of the amplifier for signal power below the saturation intensity at wavelengths between 1.49 and 1.53 µm (S-band). This shows an empirical quadratic dependence of the Nd3+∶YAG power with respect to the Ti∶Sapphire power in order to obtain the maximum photon conversion efficiency making the optimised amplifier employable as a booster amplifier in the supporting telecommunication band.

Tm3+-doped ZBLAN fibre amplifier at 1.49 [micro sign]m with co-operative lasing at 1.88 [micro sign

The limiting effect of the self-terminating 3H4-3F4 transition on the gain of a thulium ZBLAN fibre amplifier has been reduced by the integration of a fibre ring cavity into the amplifier. The ring cavity allows co-operative laser oscillation at 1.88 µm, enhancing the obtainable gain. A gain of 11 dB was observed at 1.49 µm for a 4 m fibre length.