High-energy dissipative solitons generation from a large normal dispersion Er-fiber laser

Stationary and pulsating vector dissipative solitons in nonlinear multimode interference based fiber lasers

Rapid progress in real-time spectroscopy uncovers the spatio-spectral scenarios of ultrashort pulses in dissipative systems. Varieties of transient soliton dynamics on different timescales have been revealed. Here, we report on an experimental observation of stationary and pulsating vector dissipative solitons in a nonlinear multimode interference (NL-MMI) based fiber laser with net normal dispersion. Polarization non-discrimination of the NL-MMI mode-locking facilitates the dissipative soliton trapping process. Two orthogonally polarized components are coupled together through oppositely shifting their central frequencies to form the group-velocity-locked vector dissipative solitons (GVLVDSs). Dispersive Fourier transform (DFT) based polarization resolved measurement enables insights into the transient polarization dynamics and the long-term evolution. Particularly, both stationary and pulsating GVLVDSs are obtained with appropriate parameter settings. It is found that the quasi-stationary pulsating manner is accompanied with recurrent spectral breathing and energy oscillation; the two orthogonally polarized components possess synchronous pulsating manners due to the cross-phase modulation induced trapping mechanism and the similar formation process. Additionally, chaotic pulsation is also captured in sense that the spectra cannot recover to their original profiles despite of the harmonic energy oscillation. All these findings can enhance our understanding towards soliton pulsation with the freedom of vectorial degree.

Dissipative soliton resonance in a mode-locked Nd-fiber laser operating at 927 nm

We demonstrate for the first time, to our knowledge, an all-polarization-maintaining double-clad neodymium fiber laser operating in the dissipative soliton resonance (DSR) regime where stable mode-locking is achieved using a nonlinear amplifying loop mirror (NALM) with large normal dispersion in a figure-8 cavity design. The laser thereby generates square-shaped nanosecond pulses whose duration linearly scales with pump power from 0.5 up to 6 ns, with a maximum energy of 20 nJ. In addition, output pulses feature a remarkably narrow bandwidth of 60 pm along with a signal-to-noise ratio higher than 80 dB. This study then paves the way toward using such DSR-based sources for efficient frequency doubling in the blue spectral range.

Large Normal Dispersion Mode-Locked Erbium-Doped Fiber Laser

We report on a passively mode-locked oscillator based on an erbium-doped dual concentric core fiber combining high normal dispersion and large mode area. This large normal dispersion laser generates long pulses with 30 ps duration and 0.17 nm spectral width at 1530 nm wavelength. The source delivers an average power of 64 mW at a repetition rate of 16 MHz, corresponding to 4 nJ energy. This concept opens up new degrees of freedom in the design of mode-locked fiber lasers.

Single and dual-wavelength noise-like pulses with different shapes in a double-clad Er/Yb fiber laser

We report an experimental study of passive harmonic mode-locking in an all-fiber switchable dual-wavelength Er/Yb double-clad laser. The proposed scheme supports single- and dual-wavelength operation of mode-locked pulses with rectangular, h-like and trapezoidal shapes in a noise-like pulse regime. Single-wavelength emissions at λ₁ = 1545.1 and λ₂ = 1563.6 nm were obtained for pump power values of 9.42 and 6.31 W, achieving pulse durations of up to 18 and 11.8 ns, respectively. At an intermediary pump power of 7.5 W, dual-wavelength emission is obtained and pulses of around 3.59 ns are generated. Additionally, the transition dynamics until 4th-order harmonic mode-locking is also observed. Different laser operation regimes of fundamental and different orders of harmonic mode-locking, with rectangular, h-shaped or trapezoidal shaped pulses are obtained with the same laser configuration with simple and well-defined plates and pump power adjustments.

Fine-structure oscillations of noise-like pulses induced by amplitude modulation of nonlinear polarization rotation

The generation and evolution processes of noise-like pulses (NLPs) in an all-normal-dispersion nonlinear polarization rotation (NPR) mode-locked Yb-doped fiber laser are numerically and experimentally investigated. We demonstrate that the amplitude modulation induced by reverse saturable absorption and the peak-power-limiting effect of the NPR plays a key role in the formation of fine-structure oscillations of NLPs. The width variation of the NLPs is also discussed in detail.

All-fiber highly chirped dissipative soliton generation in the telecom range

A high-energy (0.93 nJ) all-fiber erbium femtosecond oscillator operating in the telecom spectral range is proposed and realized. The laser cavity, built of commercially available fibers and components, combines polarization maintaining (PM) and non-PM parts providing stable generation of highly chirped (chirp parameter 40) pulses compressed in an output piece of standard PM fiber to 165 fs. The results of the numerical simulation agree well with the experiment. The analyzed intracavity pulse dynamics enables the classification of the generated pulses as dissipative solitons.

Optimal design of similariton fiber lasers without gain-bandwidth limitation

We have numerically investigated broadband high-energy similariton fiber lasers, demonstrated that the self-similar evolution of pulses can locate in a segment of photonic crystal fiber without gain-bandwidth limitation. The effects of various parameters, including the cavity length, the spectral filter bandwidth, the pump power, the length of the photonic crystal fiber and the output coupling ratio have also been studied in detail. Using the optimal parameters, a single pulse with spectral width of 186.6 nm, pulse energy of 23.8 nJ, dechirped pulse duration of 22.5 fs and dechirped pulse peak power of 1.26 MW was obtained. We believe that this detailed analysis of the behaviour of pulses in the similariton regime may have major implications in the development of broadband high-energy fiber lasers.

High-energy femtosecond amplifier-similariton Er-doped fiber oscillator

We demonstrated high-energy femtosecond amplifier-similariton oscillators with predominant Er-doped fibers of normal dispersion. Stably mode-locked pulses of ~3 ps, 33 nJ were produced at 720 mW pump power, while a double-pass grating pair of 36% efficiency compressed the pulses to 156 fs and 47 kW peak power (a new record). Broad mode-locked spectra supporting transform-limited pulsewidths down to 60 fs were obtained by adjusting the intracavity waveplates and filter. Continuous wave (CW) mode-locked pulses up to 53 nJ were generated by increasing the pump power to 1.5 W and by introducing significant spectral phase modulation via an intracavity pulse shaper. However, weak subpulses or pedestal could arise along with increased shot-to-shot fluctuation under this extreme operation mode.