Deqin Ouyang

Observation of Dissipative Soliton Resonance in a Net-Normal Dispersion Figure-of-Eight Fiber Laser

High-energy square pulses operating in dissipative soliton resonance region are experimentally observed in an erbium-doped figure-of-eight fiber laser with large net-normal dispersion for the first time to our knowledge. The dissipative soliton resonance is achieved by using the nonlinear-amplifying-loop-mirror mode-locked technique. The output pulse duration broadens linearly with the increase of pump power, while the peak power maintains a constant value. At the maximum pump power of 620 mW, the intracavity pulse energy is up to 379.2 nJ, and the average output power is 14.02 mW.

Double Cladding Seven-Core Photonic Crystal Fibers With Different GVD Properties and Fundamental Supermode Output

We fabricated three kinds of double cladding nonlinear seven-core photonic crystal fibers (PCFs) with different group velocity dispersion (GVD) properties and fundamental supermode output. Pumped by a 150 ps polarization maintaining a ytterbium-doped fiber laser based on the gain-switched technique, octave-spanning supercontinua were generated within the wavelengths from 450 to at least 2000 nm in these fibers with a high spatial quality.

152 fs nanotube-mode-locked thulium-doped all-fiber laser

Ultrafast fiber lasers with broad bandwidth and short pulse duration have a variety of applications, such as ultrafast time-resolved spectroscopy and supercontinuum generation. We report a simple and compact all-fiber thulium-doped femtosecond laser mode-locked by carbon nanotubes. The oscillator operates in slightly normal cavity dispersion at 0.055 ps2, and delivers 152 fs pulses with 52.8 nm bandwidth and 0.19 nJ pulse energy. This is the shortest pulse duration and the widest spectral width demonstrated from Tm-doped all-fiber lasers based on 1 or 2 dimensional nanomaterials, underscoring their growing potential as versatile saturable absorber materials.

100 W dissipative soliton resonances from a thulium-doped double-clad all-fiber-format MOPA system.

In this paper, we first achieve nanosecond-scale dissipative soliton resonance (DSR) generation in a thulium-doped double-clad fiber (TDF) laser with all-anomalous-dispersion regime, and also first scale the average power up to 100.4 W by employing only two stage TDF amplifiers, corresponding to gains of 19.3 and 14.4 dB, respectively. It is noted that both the fiber laser oscillator and the amplification system employ double-clad fiber as the gain medium for utilizing the advantages in high-gain-availability, high-power-handling and good-mode-quality-maintaining. DSR mode-locking of the TDF oscillator is realized by using a nonlinear optical loop mirror (NOLM), which exhibits all-fiber-format, high nonlinear and passive saturable absorption properties. The TDF oscillator can deliver rectangular-shape pulses with duration ranging from ~3.74 to ~72.19 ns while maintaining a nearly equal output peak power level of ~0.56 W, namely peak power clamping (PPC) effect. Comparatively, the two stage amplifiers can scale the seeding pulses to similar average power levels, but to dramatically different peak powers ranging from ~0.94 to ~18.1 kW depending on the durations. Our TDF master-oscillator-power-amplifier (MOPA) system can provide a high power 2-μm band all-fiber-format laser source both tunable in pulse duration and peak power.

Tunable and Switchable Dual-Wavelength Dissipative Soliton Operation of a Weak-Birefringence All-Normal-Dispersion Yb-Doped Fiber Laser

We report on the generation of tunable and switchable dual-wavelength dissipative solitons (DSs) in a weak-birefringence all-normal-dispersion Yb-doped fiber laser based on the nonlinear polarization rotation technique. By virtue of the weak-birefringence operation, the switchable dual-wavelength DSs with a wide wavelength-tunable range and variable wavelength spacing are observed for the first time. The variable wavelength spacing is a result from the similar order of magnitude between the polarization controller-induced birefringence change and the fiber birefringence. It is suggested that a widely tunable wavelength spacing of the tunable and switchable dual-wavelength DSs could be realized through introducing an extra birefringence change whose magnitude is comparable with the fiber birefringence.

Theoretical and experimental analysis of splicing between the photonic crystal fiber and the conventional fiber using grin fibers

Photonic crystal fibers (PCFs) are widely used in all-fiber, high-power lasers and supercontinuum sources. However, the splice loss between PCFs and conventional fibers limits its development. Grin fibers and coreless fibers were used as a fiber lens to achieve low-loss, high-strength splicing between PCFs and single-mode fibers (SMFs). The beam propagation method was used to optimize the lengths of grin fibers and coreless fibers for a minimum splice loss. The splice loss changing with the lengths of grin fiber, coreless fiber, and the air-hole collapsed region was systematically studied theoretically and experimentally. Ultimately, a minimum splice loss of 0.26 dB at 1064 nm was realized between a high-nonlinear PCF and a conventional SMF with this method.

110 W All Fiber Actively Q-Switched Thulium-Doped Fiber Laser

We report a 100-W-level, repetition rate and pulsewidth tunable, all-fiber, thulium-doped master oscillator power amplifier system. The master oscillator was actively Q-switched by a fiber-coupled acousto-optic modulator. The generated pulsewidth could be tuned from 1.16 μm to 46.3 ns by adjusting modulation repetition rate from 1 kHz to 2 MHz, and the pulse repetition rate (PRR) can also be tuned from 1 kHz to 2 MHz, correspondingly. The maximum output power could be boosted to > 110 W (slope efficiency of 55%) through three-stage thulium-doped fiber (TDF) amplifiers at PRR from 100 kHz to 2 MHz. The spectrum bandwidth was about 0.8 nm at the maximum output power without obvious indication of nonlinear effects. To the best of our knowledge, this is the first demonstration of > 110-W, all-fiber, actively Q-switched TDF laser, and it has realized the largest tuning ranges both with the pulsewidth and the PRR.

A low-cost CW-pumped supercontinuum source

In order to resolve the conflict of high performance and high cost for a continuous wave (CW)-pumped supercontinuum (SC) source under low-power pumping conditions (less than ~20 W), a cascaded-fiber configuration of a short photonic crystal fiber (PCF) and a short low-cost conventional fiber is proposed to replace long high-cost PCFs. By cascading a 60 m low-cost conventional nonlinear fiber with a 90 m PCF pumped by a 24 W CW fiber laser, a higher-quality SC with a 10 dB bandwidth of 230 nm and a 5 dB bandwidth of 176 nm is demonstrated. This SC also has a maximum output power of 13.9 W. Both the spectral performance and the output power properties for this SC source are superior to those for the SC from the 200 m high-cost PCF, and these results demonstrate the effectiveness of the method in realizing a low-cost, high-quality SC source.

70-W Graphene-Oxide Passively Q-Switched Thulium-Doped Double-Clad Fiber Laser

We report on a graphene-oxide (GO) passively Q-switched thulium-doped double-clad fiber laser with two-stage amplifiers that can deliver >70 W average power at ~1950.27 nm wavelength. The achieved highest average power is ~73 W, corresponding to ~1.5 μs pulse duration, ~0.877 mJ pulse energy, and ~585 W peak power. To our best knowledge, this is the first high-power pulsed output by using passive method to generate Q-switched pulses, especially by using GO as the saturable absorber, paving the way toward practical application of GOSA in high power pulsed double-clad fiber laser system.

Optimized flat supercontinuum generation in high nonlinear fibers pumped by a nanosecond Er/Yb Co-doped fiber amplifier

Flat supercontinuum generation has been demonstrated in high nonlinear fibers with zero dispersion wavelengths at 1480 and 1500 nm, which were pumped by a MOPA structured Er/Yb co-doped fiber amplifier based on a modulated nanosecond seed laser with the wavelength of 1552 nm. The spectra and output powers affected by the zero dispersion wavelengths, fiber lengths and pump pulse widths were investigated experimentally. A flat spectrum with 5 dB bandwidth from 1220 nm to beyond 1700 nm (assuming the pump peak was filtered) in the optical spectrum analyzer detectable range was finally obtained by optimizing the fiber length and pump pulse width. The maximum output power was 1.02 W, including the peaks near 1550 nm.