Soliton Fiber Laser Research Articles

Sub-90 fs dissipative-soliton Erbium-doped fiber lasers operating at 16 μm band

We present an L-band dissipative soliton (DS) fiber laser, which can deliver 87.5 fs pulses at 1.6 μm band. Numerical simulations are used to confirm the DS generation, and prove the pivotal component of the invisible filter with proper bandwidth in the formation of DS pulses. Such a robust, compact ultrafast laser source with higher pulse energy is hence an excellent seed source for L-band amplifiers. The mechanism revealed in the simulations is helpful to develop a unified theory for understanding various mode-locking regimes in normal dispersion lasers.

Gain-guided soliton fiber laser with high-quality rectangle spectrum for ultrafast time-stretch microscopy.

The ultrafast time-stretch microscopy has been proposed to enhance the temporal resolution of a microscopy system. The optical source is a key component for ultrafast time-stretch microscopy system. Herein, we reported on the gain-guided soliton fiber laser with high-quality rectangle spectrum for ultrafast time-stretch microscopy. By virtue of the excellent characteristics of the gain-guided soliton, the output power and the 3-dB bandwidth of the stable mode-locked soliton could be up to 3 mW and 33.7 nm with a high-quality rectangle shape, respectively. With the proposed robust optical source, the ultrafast time-stretch microscopy with the 49.6 μm resolution and a scan rate of 11 MHz was achieved without the external optical amplification. The obtained results demonstrated that the gain-guided soliton fiber laser could be used as an alternative high-quality optical source for ultrafast time-stretch microscopy and will introduce some applications in fields such as biology, chemical, and optical sensing.

Bound States of Dissipative Solitons in the Single-Mode Yb-Doped Fiber Laser

We present results of our research on the observation of a bound state of double dissipative-soliton operation of a passive mode-locked Yb-doped fiber laser based on the nonlinear polarization rotation mechanism through the proper adjustment of the wave plates. The generated dissipative solitons with large net positive cavity Group Velocity Dispersion (GVD) are characterized by their spectral profile of sharp peaks near edges, which are distinct from those of the conventional solitons in fiber lasers. By using an artificial saturable absorber, we have obtained stable single and double bound-state dissipative solitons. In all-normal-dispersion Yb-doped single-mode fiber lasers, the bound state of double dissipative solitons with a full-width at half-maximum of 7 ps, and a fixed pulse separation of 8 ps independent of the experimental conditions is achieved for the first time, to the best of our knowledge. Our result once again shows that the passively mode-locked fiber laser with large normal dispersion can help to explore dissipative soliton dynamics.

All-Polarization Maintaining Passively Mode-Locked Fiber Laser Using Evanescent Field Interaction With Single-Walled Carbon Nanotube Saturable Absorber

We implemented a single-walled carbon nanotube (SWCNT)-based saturable absorber (SA) that evanescently interacts with light on a side-polished polarization-maintaining fiber (PMF) platform. A high-quality SWCNT/polymer composite was spin-coated onto a side-polished PMF embedded in a quartz block, where the slow optical birefringence axis of the PMF was perpendicular to the polished surface. The fabricated in-line SA had an insertion loss of -1.5 dB with a modulation depth of 0.5% for the polarization direction associated with the transvers magnetic mode. An all-PMF laser was built using the fabricated in-line SA to demonstrate self-starting, turn-key operation of Er-doped, all-fiber lasers delivering stable scalar soliton pulses. The measured 3-dB spectral bandwidth and pulse duration of the laser output were 5.1 nm and 510 fs, respectively, resulting in a time-bandwidth product of 0.320. We examined the polarization state of the soliton fiber laser output and found that the laser stably generated linearly polarized ultrashort pulses with a polarization extinction ratio of -18.4 dB.

Femtosecond mode-locked erbium-doped fiber laser based on MoS2–PVA saturable absorber

We fabricate a free-standing few-layer molybdenum disulfide (MoS2)–polymer composite by liquid phase exfoliation of chemically pristine MoS2 crystals and use this to demonstrate a soliton mode-locked Erbium-doped fiber laser (EDFL). A stable self-started mode-locked soliton pulse is generated by fine-tuning the rotation of the polarization controller at a low threshold pump power of 25mW. Its solitonic behavior is verified by the presence of Kelly sidebands in the output spectrum. The central wavelength, pulse width, and repetition rate of the laser are 1573.7nm, 630fs, and 27.1MHz, respectively. The maximum pulse energy is 0.141nJ with peak power of 210W at pump power of 170mW. This result contributes to the growing body of work studying the nonlinear optical properties of transition metal dichalcogenides that present new opportunities for ultrafast photonic applications.

Periodic exploding dissipative solitons

We show the existence of periodic exploding dissipative solitons. These nonchaotic explosions appear when higher-order nonlinear and dispersive effects are added to the complex cubic-quintic Ginzburg-Landau equation modeling fiber soliton lasers. This counterintuitive phenomenon is the result of period-halving bifurcations leading to order (periodic explosions), followed by period-doubling bifurcations leading to chaos (chaotic explosions).

Multi-pulse operation of a dissipative soliton fibre laser based on nonlinear polarisation rotation

We report an experimental observation of multiple dissipative soliton (DS) operation states in an all-normal-dispersion passively mode-locked Yb-doped fibre laser, including DS bound and oscillating states. In the bound state, multiple DSs up to 11 can coexist in the cavity. In the oscillating state, the DSs' movements are not purely random and three typical states are generalised and illustrated. A single-pulse mode-locked state is established at a high pump power by carefully adjusting the polarisation controllers. The broad spectrum indicates that it may be noise-like pulses, which can serve as a pump to generate a supercontinuum.

32-nJ 615-fs Stable Dissipative Soliton Ring Cavity Fiber Laser With Raman Scattering

We report on a 32-nJ 615-fs stable dissipative soliton (DS) fiber laser in the presence of stimulated Raman scattering (SRS) in a long ring cavity. We found that a transition from noise-like pulses to dissipate soliton occurred at sufficiently high power in a nonlinear amplified loop mirror (NALM). Accompanied with the transition was a surge of pulse energy and suppression of Raman emission—the residual Raman emission counts only $\sim 1$ % of energy in the output pulse. We attribute this transition to the shift of the transfer function in the NALM. Our results clearly show that the DS energy can be scaled up further in a long cavity even in the presence of Raman scattering. However, despite the increase of SRS threshold, further DS energy scaling may still be limited by SRS.

Ultra-High Repetition Rate Harmonic Mode-Locking Generated in a Dispersion and Nonlinearity Managed Fiber Laser

Stable pulses with a 22.132-GHz repetition rate are successfully obtained by managing the dispersion and nonlinearity in a passively soliton erbium-doped single-mode fiber laser, which is as high as the 2192nd order of the fundamental frequency of 10.096 MHz. The super-mode suppression ratio beyond 40 dB is observed under only 485 mW pump power.

Dual-Wavelength Soliton Mode-Locked Fiber Laser With a WS<sub>2</sub>-Based Fiber Taper

Recently, few-layer WS2, as a novel two-dimensional (2D) material, has been discovered to possess both the saturable absorption effect and the huge nonlinear refractive index. In experiment, by taking advantage of the unique optical properties of 2D WS2, we fabricated a highly nonlinear photonic device using the pulsed laser beam to deposit the WS2 film onto a fiber taper. With the WS2-based fiber taper, we have demonstrated the single- and dual-wavelength soliton pulses in the erbium-doped fiber laser (EDFL) by properly adjusting the pump strength and the polarization state. According to the soliton theory, the pulse width is $\sim 220$ fs for the single-wavelength soliton, and $\sim 585$ and $\sim 605$ fs for the dual-wavelength soliton, respectively. The dual-wavelength soliton fiber laser exhibits the maximum output power of 10.1 mW and the pulse energy of $\sim 1.14$ nJ, when the pump power is increased to $\sim 420$ mW. Our findings suggest that WS2-based fiber taper could operate as both an excellent saturable absorber for obtaining a femtosecond pulse and a promising highly nonlinear photonic material for the multi-wavelength generation.

L-band wavelength-tunable dissipative soliton fiber laser.

A tunable L-band dissipative soliton (DS) fiber laser with nonlinear polarization rotation (NPR) playing the roles of both a saturable absorber (SA) and a tunable filter has been demonstrated experimentally and numerically. By appropriate adjustment of the states of the polarization controllers (PCs) and the pump power, DSs with continuously tunable wavelengths have been observed over the wavelength range from 1583.0 to 1602.4 nm with a 3-dB spectral bandwidth of around 20 nm and from 1581.9 nm to 1602.6 nm with a 3-dB spectral bandwidth of around 4 nm. In addition, we have observed that by increasing the pump power, the 3-dB spectral bandwidth of the DS could be increased without pulse breaking. Numerical results for the characteristics of the DSs are in accord with the experimental data.

Theoretical analysis of the energy evolution in dissipative soliton fiber lasers

Theoretical results on the energy evolution in ring and linear cavities of dissipative soliton fiber lasers are analyzed. The correctness of the theoretical results is confirmed by mathematical modeling.

Mechanism of solitary wave breaking phenomenon in dissipative soliton fiber lasers.

We numerically and experimentally investigate the pulse evolution to the edge of destabilization against pumping powers in a strongly dissipative-dispersive laser configuration mode locked by nonlinear polarization evolution (NPE) technique. Two distinct dynamic processes are indicated by numerical results and further evidenced by experimental observations, where one depicts the monotonous increase in peak power and slight narrowing of duration, the other is different in exhibiting obvious broadening in temporal domain. Correspondingly, it is demonstrated in the simulation of cavity dynamics that the artificial saturable absorber plays two opposite roles in pulse shaping, which implies the switch of cavity feedback. Mechanisms with respect to different cavity feedbacks are analyzed based on a newly-proposed theoretical viewpoint, for positive feedback single pulse operation is restricted by the limit of peak power mainly dependent of the gain bandwidth; for negative feedback the breakup is attributed to the limited strength of clamping effect determined by multiple ingredients.

Wideband-tunable soliton fiber laser mode-locked at 1.88 GHz by optoacoustic interactions in solid-core PCF.

We report a wavelength-tunable soliton fiber laser stably mode-locked at 1.88 GHz (the 389th harmonic of the cavity round-trip frequency) by a light-driven acoustic resonance in the core of a photonic crystal fiber. Stable high-harmonic mode-locking could be maintained when the lasing wavelength was continuously tuned from 1532 to 1566 nm by means of an optical filter placed inside the laser cavity. We report on the experimental performance of the laser, including its power scalability, super-mode noise suppression ratio, long-term repetition rate stability, short-term pulse amplitude noise and timing jitter, optical comb structure and pulse-to-pulse phase fluctuations.

High-power passively mode-locked dissipative soliton fiber laser featuring cladding-pumped non-CVD thulium-doped fiber

We are reporting on the characterization of a thulium-doped fiber laser applying new powder technology in the mode-locking regime. A high average output power of 185 mW at a repetition rate of 9 MHz was achieved directly from the oscillator, which resulted in 21 nJ of pulse energy. The single-pulse operation regime was confirmed by careful numerical modeling of the laser cavity.

Long-range soliton interactions through gain-absorption depletion and recovery.

We report the interpulse dynamics in fiber soliton laser because of depletion and relaxation of gain and absorption. The soliton interaction range is shown to depend largely on the relaxation time of dissipative parameters while the compensation of the dynamical gain and absorption depletion leads to the formation of stationary soliton groups with unequal interpulse distances.

A switchable femtosecond and picosecond soliton fiber laser mode-locked by carbon nanotubes

We propose a switchable dual-scale nanotube-mode-locking fiber laser based on a fiber loop mirror and fiber Bragg grating. The loop mirror not only works as a broadband reflector, but also a birefringence-induced filter. By adjusting the polarization controller in the loop, the operation wavelength can be switched between 1530 and 1560 nm. The femtosecond soliton at 1560 nm has a bandwidth of 5.5 nm and pulse duration of 680 fs, while the picosecond soliton is centered at 1529.5 nm with the bandwidth of 0.11 nm and pulse duration of 23.3 ps. The dual-scale solitons display more than 30 times a difference of pulse width, as well as distinct spectral bandwidth, repetition rate, and pulse energy. Our study provides the flexibly switchable ultrashort pulse sources at femtosecond and picosecond scales, which are suitable for practical applications.

Nonlinear optical absorption of few-layer molybdenum diselenide (MoSe_2) for passively mode-locked soliton fiber laser [Invited

In this paper, both nonlinear saturable absorption and two-photon absorption (TPA) of few-layer molybdenum diselenide (MoSe2) were observed at 1.56 μm wavelength and further applied to mode-locked ultrafast fiber laser for the first time to our knowledge. Few-layer MoSe2 nanosheets were prepared by liquid-phase exfoliation method and characterized by x ray diffractometer, Raman spectroscopy, and atomic force microscopy. The obtained few-layer MoSe2 dispersion is further composited with a polymer material for convenient fabrication of MoSe2 thin films. Then, we investigated the nonlinear optical (NLO) absorption property of the few-layer MoSe2 film using a balanced twin-detector measurement technique. Both the saturable absorption and TPA effects of the few-layer MoSe2 film were found by increasing the input optical intensity. The saturable absorption shows a modulation depth of 0.63% and a low nonsaturable loss of ∼3.5%, corresponding to the relative modulation depth of 18%. The TPA effect occurred when the input optical intensity exceeds ∼260 MW/cm2. Furthermore, we experimentally exploit the saturable absorption of few-layer MoSe2 film to mode lock an all-fiber erbium-doped fiber laser. Stable soliton mode locking at 1558 nm center wavelength is achieved with pulse duration of 1.45 ps. It was also observed that the TPA process suppresses the mode-locking operation in the case of higher optical intensity. Our results indicate that layered MoSe2, as another two-dimensional nanomaterial, can provide excellent NLO properties (e.g., saturable absorption and TPA) for potential applications in ultrashort pulse generation and optical limiting.

Pump hysteresis and bistability of dissipative solitons in all-normal-dispersion fiber lasers

We report the results of numerical simulations on pump hysteresis and bistability of a dissipative soliton fiber laser. The fiber laser is made of normal-dispersion fibers and passively mode locked by using the nonlinear polarization rotation technique. The dependence of the final steady state on the initial light field is investigated. Bistability between the single-pulse state and the double-pulse state in the mode-locking regime is demonstrated. Different initial conditions could lead to different attractors, even with the same point in the parameter space.

Soliton mode-locked fiber laser based on topological insulator Bi_2Te_3 nanosheets at 2 μm

We reported diverse soliton operations in a thulium/holmium-doped fiber laser by taking advantage of a tapered fiber-based topological insulator (TI) Bi2Te3 saturable absorber (SA). The SA had a nonsaturable loss of ∼53.5% and a modulation depth of 9.8%. Stable fundamentally mode-locked solitons at 1909.5 nm with distinct Kelly sidebands on the output spectrum, a pulse repetition rate of 21.5 MHz, and a measured pulse width of 1.26 ps were observed in the work. By increasing the pump power, both bunched solitons with soliton number up to 15 and harmonically mode-locked solitons with harmonic order up to 10 were obtained. To our knowledge, this is the first report of both bunched solitons and harmonically mode-locked solitons in a fiber laser at 2 μm region incorporated with TIs.