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.
A high-energy, wavelength-tunable all-fiber picosecond MOPA laser is reported. The seed is provided by an active mode-locked oscillator which can be continuously tuned from 1030 nm to 1080 nm. The seed pulses with duration of 212 ps and average power of 3 mW are injected into a two-stage amplifier. The nonlinear effect in the main amplifier is alleviated by using a large mode area gain fiber, to avoid pulse distortion and spectral broadening. Over 10 W average output power ranged from 1030 nm to 1080 nm is achieved with the FWHM bandwidth and spectral signal-to-noise ratio of 0.2 nm and 30 dB, respectively. Measured pulse duration is less than 350 ps at repetition rate of ~536 kHz. The maximum peak power and single pulse energy reaches 54 kW and 18 μJ, respectively. The source is then used to pump a self-designed multi-core photonic crystal fiber (PCF) for supercontinuum generation. By tuning the wavelength of the laser to approach the zero-dispersion wavelength of the PCF, a broadband supercontinuum covering the wavelength range from shorter than 400 nm to longer than 2400 nm is achieved. The experimental results are in consistent with the theoretical analysis, which benefit from the wavelength continuously tunable property and the high peak power of the picosecond laser.
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.
The effectiveness and efficiency of laser processing depends on absorption characteristics of materials. A combination of a low-energy supercontinuum with a high-energy narrowband laser was proposed to form a potential new laser source for materials processing. The broadband spectrum of the supercontinuum is expected to slightly change the properties of target materials by materials absorption, and then the narrowband laser is able to process the materials effectively. This new laser source was realized by seed pulse-shaping. The seed pulses were formed by a high and short pulse with a low and long pulse, which were generated from an electrically modulated laser diode operating at 1064nm. After being amplified, the pulses went through a section of photonic crystal fiber. The average output power and spectrum could be widely tuned as the pulse durations, amplitudes and relative delay time varied.
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