Xiushan Zhu

10-W-level diode-pumped compact 2.78 μm ZBLAN fiber laser

We report on >9W transverse-fundamental-mode CW output near 3 μm from a 4m heavily erbium-doped ZBLAN double-clad fiber laser pumped by a collimated 100 W 975 nm laser diode array. The pump threshold of the fiber laser was about 1W, and the slope efficiency was 21.3%. The peak wavelength of free running was about 2708 nm at low pump power and moved to around 2785 nm at high pump power. Output of 9W was obtained when the launched pump power was 42.8W. The output, however, fluctuated intensively like a pulsed laser, and the operation broke down with optical damage of the pumping end facet when the pump was increased beyond 42.8 W. Therefore, alleviation of the operation fluctuation, heat management, and strengthening the pumping fiber are crucial considerations for the stable operation of 10-W-level mid-IR ZBLAN fiber lasers.

Compact 2 W wavelength-tunable Er:ZBLAN mid-infrared fiber laser.

We report a high-power diode-pumped wavelength-tunable (2.7-2.83 mum) erbium-doped ZBLAN mid-infrared fiber laser. Continuous-wave output of >2 W with a spectral linewidth of 1.27 GHz was obtained. Nevertheless, the wavelength-tunable range was found to shrink with increasing pump power. The gain bandwidth narrowing under strong pumping may be ascribed to the enhanced reabsorption process and the weakened population inversion associated with shorter-wavelength emissions.

Watt-level Er-doped and Er-Pr-codoped ZBLAN fiber amplifiers at the 2.7-2.8 μm wavelength range

Characteristics of diode-pumped Er-doped and Er-Pr-codoped ZBLAN fiber amplifiers were investigated at the 2.7-2.8 microm wavelength range. An amplified signal of 4.6 W was obtained from the singly Er-doped amplifier for an input signal of 110 mW, corresponding to a net gain of 16.2 dB. An amplified signal of 2.65 W was obtained from the Er-Pr-codoped amplifier for an input signal of 70 mW, corresponding to a net gain of 15.8 dB. It is found that the gain bandwidth of the singly Er-doped amplifier is much narrower than that of the Er-Pr-codoped amplifier. Small gain, no gain, or even a loss for shorter-wavelength signals propagating through the singly Er-doped amplifier should attribute for the large number residual populations in the lower laser level caused by the inefficient depopulation of the energy transfer upconversion processes.

Numerical analysis and experimental results of high-power Er/Pr:ZBLAN 2.7 μm fiber lasers with different pumping designs

Gain factor and output performance of erbium-praseodymium codoped ZBLAN double-clad fiber lasers at 2.7 microm with different pumping designs were calculated and analyzed. Single-end backward pumping with a highly reflective mirror butted against one fiber end and dual-end pumping with Fresnel reflections from both fiber ends were found to be the most efficient pumping designs. Ten-watt-level Er/Pr:ZBLAN fiber lasers proved to be achievable with recent diode laser and ZBLAN fiber technologies. Their corresponding optimum fiber lengths for different pumping configurations were determined. It was also found that fiber lasers with a flat evolution of gain factor can obtain the largest output power. Experimental results of 4 m and 12 m fiber lasers showed very good agreement with simulation results.

Watt-Level 100-nm Tunable 3-

Watt-level erbium-praseodymium codoped ZBLAN midinfrared fiber laser with 100-nm continuously wavelength-tunable range (2.7-2.8 m) is demonstrated. Continuous-wave output of 1 W with a linewidth of 1.8 GHz over the entire tuning range is affordable. Owing to relatively small residual populations in the lower laser level I of Er ions in the Er-Pr-codoped system, the wavelength-tunable range shrinking with increasing pump power, which always happens in tunable singly Er-doped ZBLAN fiber lasers, was not observed in this tunable Er-Pr-codoped fiber laser.

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The 10-Watt-level diode pumped erbium-doped ZBLAN fiber lasers at 2.7 /spl mu/m under different ways of pumping are studied and analyzed through numerical simulations. Experiments on a fiber laser with output power of 5.4 W are described.

m Fiber Laser

We report a high power diode-pumped mid-IR fiber amplifier at 2.7 mum. 4.6 W amplified signal was obtained for an input signal of 110 mW, corresponding to a net gain of 16.2 dB.

Scaling up laser diode pumped mid-infrared fiber laser to 10-watt-level

10-Watt-level diode pumped erbium-doped ZBLAN fiber lasers at 2.7 mum were demonstrated. 8 W output was obtained by dual-end pumping a piece of 4 m 60,000 ppm heavily erbium-doped double-clad fiber.

5 W diode-pumped mid-infrared fiber amplifier

We report the first demonstration of high power mid-IR (2.7 /spl mu/m) fiber amplifiers. 2.45 W of amplified output power was obtained for an input signal of 70 mW, corresponding to a net gain of 15.4 dB.

Demonstration of ≫ 8 Watt output from laser diode pumped mid-infrared fiber lasers

We report studies of SBS in optical fibers with the goal of using SBS phase conjugation as a passive beam combiner to build high power (>100 W cw) all fiber laser sources. We propose the development of a near infrared high power fiber laser by phasing two Er doped amplifiers in parallel using stimulated Brillouin scattering in a multimode fiber. We use a 1.5 p.m master oscillator-power amplifier configuration (MOPA) to generate SBS in a multimode fiber. The fiber amplifier consists of two Er doped multimode fiber amplifiers (diode pumped), in parallel, which will combine to generate SBS in the multimode fiber.