We reported the first erbium-doped ZBLAN fiber MOPA system centered at 2789 nm. The master oscillator was a passively mode-locked ZBLAN fiber laser based on a semiconductor saturable absorber mirror in a linear cavity. The pulse repetition rate was measured as 15.3 MHz with a signal-to-noise ratio of 62 dB, which indicating stable mode-locking operation. Then a one-stage Er3+-doped ZBLAN fiber amplifier was used to boost the average output power after a polarization dependent isolator. The maximum output power of 0.7 W was measured at the end of the amplifier with a slope efficiency of 25%. And the width of 3 dB spectrum was 4.5 nm from 2787.5 nm to 2792 nm.
For pulsed fiber amplifiers with repetition rate of tens of kHz, inter-pulse amplified spontaneous emission (ASE) is easy to build up and makes it difficult to amplify the weak signal effectively. Besides, amplified pulse shape of several tens of nanosecond would distort because of the dynamic gain saturation effect. In this paper, we demonstrate a polarization-maintained fiber laser system with three-stage amplifiers delivering pulse energy up to 70 μJ. The whole system is seeded by a semiconductor diode laser with central wavelength of 1063.9 nm and pulse repetition rate of 10 kHz which is driven directly by an arbitrary waveform electrical signal. We experimentally optimized the gain fiber length of the first-stage amplifier based on the reabsorption effect. The signal amplification efficiency and ASE proportion with different pump schemes in the first amplifier were investigated and compared in detail. Finally, an amplified pulse with 70 μJ energy accompanying with serious shape distortion was experimentally demonstrated. The signal to ASE ratio is as high as 54 dB from spectrum and the overall energy gain is 30 dB. Furthermore, a rectangular pulse with energy of 50 μJ was achieved by pre-compensating the shape distortion using the stochastic parallel gradient descent (SPGD) algorithm and the total energy gain is 28.5 dB.
A strictly-all-fiberized 2 to 5 μm supercontinuum (SC) laser source with high conversion efficiency is demonstrated. A broadband thulium-doped fiber amplifier with spectral coverage of 2-2.7 μm is used to pump a piece of single-mode fluoroindate (InF3) fiber. A fusion spliced joint with loss down to 0.07 dB is achieved between a piece of silica fiber and the InF3 fiber, which keeps all-fiber structure and efficient pump power coupling. A 1.35-W SC with spectral coverage of 1.5-5.2 μm is obtained with a record power conversion efficiency of 59.5%. This research, to the best of the authors' knowledge, demonstrates the first all-fiber-integrated of InF3-fiber-based MIR-SC laser sources to date.
An all-fiber midinfrared supercontinuum with 20-dB spectral coverage from 1.9 to 4.6 μm is demonstrated with a record power ratio beyond 3.8 μm. The supercontinuum is generated in a piece of single-mode ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) fiber pumped by a broadband, single-mode thulium-doped fiber amplifier. Under the optimized pulse repetition rate and ZBLAN fiber length, the output spectrum has a good flatness. The power ratio beyond 3.8 μm is measured to be over 30% when the average output power reaches 1.11 W. Based on the all-fiber configuration, we have provided a compact, reliable, and promising supercontinuum source for further spectral extension into the midinfrared region where a high long-wavelength ratio is preferred.
In this letter we have demonstrated, an all-fiber Ho-doped fiber laser working on the noise-like pulse regime based on nonlinear polarization rotation (NPR). The 18.3 nm spectral bandwidth was obtained at the central wavelength of 2133 nm, with the maximum output power of 68.6 mW. To the best of our knowledge, it is the first Ho-doped fiber laser working in noise-like pulse regime. The evolvement among different pulse regimes was also investigated in this experiment.
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