Hybrid Mode-locked Fiber Laser Research Articles

L-band wavelength-switchable bound states in a hybrid mode-locked fiber laser

L-band wavelength-switchable bound states in a hybrid mode-locked fiber laser

Self – assembled aligned single – walled carbon nanotubes as an anisotropic polarizer and saturable absorber in erbium-doped femtosecond fiber laser

We report the production of a saturable absorber (SA) based on aligned single-walled carbon nanotubes SWCNTs by the self-assembly method. The ultrafast saturation behavior of prepared aligned and random nanostructures shows an increase of modulation depth by 6% due to the alignment method. We also observed the dependence of aligned SWCNTs loss on the polarization direction of laser radiation. All-fiber Er-doped hybrid mode-locked fiber laser was demonstrated based on the aligned /random SWCNTs-based SAs. We achieved the generation of stable stretched pulses with a pulse duration of 490/569 fs and an average output power of 20.7/18.25 mW. We also investigated the advantages of using aligned SWCNTs compared to the typical structure with random tube distribution. We show that the use of aligned SWCNTs film increased the SNR by 24.5, decreased the mode-locking threshold power by 42 mW, and decreased the RIN level by (20-25) dB in the frequency range [∼ 0 Hz- 100 kHz] and ∼ 8 dB in the range [100 kHz – 1 MHz].

Tunable multi-wavelength all polarization-maintaining hybrid mode-locked Yb-doped fiber laser

We demonstrate an all polarization-maintaining (all-PM) mode-locked ytterbium-doped fiber laser (YDFL) based on a semiconductor saturable absorber mirror and nonlinear polarization evolution. The laser can produce tunable dual-wavelength from 1019.75 nm to 1038.68 nm, and triple-wavelength from 1021.28 nm to 1038.35 nm. To our knowledge, this is the first report of tunable dual- and triple-wavelength mode-locked operation in all-PM mode-locked YDFL. Furthermore, numerical simulations have demonstrated the multi-wavelength genesis and dynamic evolution. Our research proposes an innovative approach to achieving tunable multi-wavelength in all-PM fiber laser and lays the groundwork for a new type of all-PM tunable stabilized laser source.

Tunable and switchable multi-wavelength mode-locked fiber lasers induced by an optimized hybrid mode-locked composite filtering effect.

A multi-wavelength mode-locked fiber laser can generate different wavelengths from a single laser cavity, offering potential as a dual-frequency comb and serving as an ideal light source for terahertz wave generation. We present an optimized hybrid mode-locked Er-doped fiber laser with flexible outputs: switchable and tunable dual-wavelength mode-locking, along with stable tri-wavelength mode-locking, which is achieved by introducing 0.69 m polarization-maintaining fiber and bent 200 m single-mode fiber to enhance intra-cavity birefringence and nonlinear effect to optimize the hybrid mode-locking effect, that is, build the composite filter effect. The dual-wavelength mode-locking not only covers a tunable wavelength range of 5 nm but also provides tunable wavelength intervals of 4-26 nm due to the composite filter effect. The formation dynamics of the tri-wavelength mode-locking can be switched either pair-by-pair or one-by-one. This approach enables the realization of wavelength interval tunable dual-wavelength mode-locking in mode-locked fiber lasers simply by introducing fiber without additional actions. Such a simple, compact fiber laser with tunable wavelength capabilities holds significant potential for diverse applications.

Tm–Ho co-doped hybrid mode-locked fiber laser based on Ti3CNTx saturable absorber

We proposed a thulium-holmium (Tm–Ho) co-doped hybrid mode-locking fiber laser utilizing few-layer Ti3CNTx MXene saturable absorber. The Ti3CNTx material exhibits superior optical properties with a saturation intensity of 25 mW and a modulation depth of 18.32%. By integrating nonlinear polarization rotation (NPR) technology with Ti3CNTx-SA, we achieved a self-starting, low threshold, ultra-stable and, efficient hybrid mode-locking pulse. The pulses are generated at a central wavelength of 1959.23 nm, with a 3 dB bandwidth of 5.34 nm and a pulse width of 766 fs. Compared to the single NPR technology, the structure reduces the self-starting threshold for mode-locking, compresses the pulse width by at least 21 fs, and significantly improves the signal-to-noise ratio. The proposed laser underscores the potential application and broad prospects of Ti3CNTx-SA in the 2-μm field of ultrafast fiber lasers.

Wavelength tunable noise-like pulses in a hybrid mode-locked erbium-doped fiber laser

The study demonstrates a new type of laser that generates wavelength-tunable h-shaped noise-like pulses (NLPs). We incorporated the nonlinear polarization rotation (NPR) mechanism into a figure-eight erbium-doped hybrid mode-locked fiber laser based on the nonlinear amplifier loop mirror (NALM). Under an intra-cavity net dispersion of −5.535 ps2, the system produced NLPs with a maximum pulse duration of 24.54 ns, a maximum single energy of 19.96 nJ and a maximum output average power of 14.46 mW when the pump power was set to 543 mW. By adjusting the pump power and fine-tuning the polarization controller, the laser can output NLPs with tunable wavelengths ranging from 1560 to 1601 nm. The flexibility of wavelength-tunable techniques has potential applications in laser detection, high-energy physics experiments, and other fields, enriching the research framework of noise-like applications.

Hybrid mode-locked fiber laser based on nonlinear optical loop mirror and manganese phosphorus triselenide (MnPSe3) coated arc-shaped fiber

This study investigates a hybrid mode-locked fiber laser incorporating manganese phosphorus triselenide (MnPSe3) saturable absorber and nonlinear optical loop mirror (NOLM), yielding profound insights into its potential and performance. The hybrid mode-locked laser showcased an output spectrum centered at 1549 nm with an expanded 3-dB bandwidth of 12.25 nm. It generates remarkably narrow pulses, with a pulse width of 240 fs. The mode-locking operates at a repetition rate of 5.71 MHz, with a high signal-to-noise ratio (SNR) of 58 dB, and achieves an average output power of 299 mW with a pulse energy of 52.36 nJ and peak power of 218 kW. These findings underscore the potential of the hybrid mode-locking configuration utilizing MnPSe3 to enhance mode-locked pulse generation significantly compared to the NOLM configuration.

Coexistence and competition: Double attractors in hybrid mode-locked fiber lasers

The hybrid mode-locking technique has been widely used in enhancing pulse quality, but the specific mechanism of hybrid mode-locking remains unclear. In this work, we experimentally investigate three pulse formation mechanisms in saturable absorbers (SA) and nonlinear polarization evolution (NPE) passively hybrid mode-locked fiber laser, which are SA domination, NPE domination, and SA-NPE co-domination switching and clarified the existent dynamic competition and cooperation between the two mode-locking mechanisms of the hybrid mode-locked fiber laser. The method of simulating the filtered gain spectrum with customized filtering is proposed, and the switching of pulse formation mechanisms is numerically investigated using the coupled Ginzburg–Landau equations. The presence of a double attractor subsystem in a hybrid mode-locked fiber laser is proposed and demonstrated. Our results deepen the understanding of hybrid mode-locked fiber lasers and provide experimental ideas for the study of multi-attractor coexistence.

Generation of sub-100 fs pulses from a SESAM-NPE hybrid mode-locked Yb-doped fiber laser at a fundamental repetition rate of 1.15 GHz.

Supercontinuum generation via direct pumping of unamplified high-repetition-rate, sub-100fs pulses with a pulse energy lower than 50pJ is superior in noise performance and features a high acquisition speed. We demonstrate a novel, to the best of our knowledge, gigahertz-repetition-rate, mode-locked Yb-doped fiber laser, where the hybrid mode-locking approach is employed. The laser has a low initiating threshold of 300mW and a broad mode-locking range of 600mW (300-900mW) in terms of pump power. The shortest obtained pulse width of the laser after compression is 95fs, and the highest output pulse energy is 92.9 pJ at a fundamental repetition rate of 1.15GHz. Moreover, the laser's output polarization states are switchable, and it has a polarization extinction ratio of 17.9dB.

Transient multi-soliton dynamics between adjacent-order harmonic mode-locking states in a hybrid mode-locked fiber laser

The buildup dynamics from noise-seeded relaxation oscillation to harmonic mode-locking (HML) solitons generation have been well investigated in ultrafast fiber lasers. However, the transient multi-soliton dynamics in higher-order HML states are still attractive yet largely unexplored. We reveal here that, the experimental observation of the multi-soliton dynamics including soliton beating dynamics, soliton annihilation, transient bound state, two-soliton resonance state, soliton splitting, and multi-soliton repulsion dynamics are analyzed by the emerging time-stretched dispersive Fourier transform (TS-DFT) technique. Particularly, the excessive intracavity energy result in the double-pulse pulsating with transient bound states and three types of soliton molecules states can be observed in the earlier and middle part of the transition process. Numerical results further reveal that several similar multi-soliton dynamics operating at stable 2nd and 3rd states could be caused by a fine tuning of the pump power level in a hybrid mode-locked laser. Our results unveil a diverse set of ultrafast transient process in fiber lasers, and open up new ways into obtaining and controlling the generation of high-repetition-rate ultrashort pulses in fiber lasers.

Real-time transition dynamics of harmonic mode-locking states with spectral filtering effect in a hybrid mode-locked fiber laser

We experimentally investigated the transition dynamics between 2nd and 3rd harmonic mode-locking states using the dispersive Fourier transform technology in a hybrid mode-locked fiber laser. Keeping the pump power unchanged and adjusting polarization controller to change intracavity-loss-dependent gain profile and the spectral filtering effect, a set of soliton dynamics induced by soliton interaction are revealed before the soliton splitting. Solitons undergo similar oscillation behaviors during the reverse decay process of the harmonic mode-locking order until one of the solitons disappears. In these transient dynamics, a significant wavelength shift phenomenon could be observed in the transition process of harmonic orders. The numerical results further show that intracavity spectral filtering effects play key role in the harmonic order transition dynamics process, consistent with experimental results. It provides new insights into the evolution and dynamics behavior in harmonic mode-locked soliton order conversion and its potential applications.

High-energy femtosecond pulse generation from a hybrid mode-locked large-mode-area Er:ZBLAN fiber laser.

We report a hybrid mode-locked fiber laser at 2.8 µm based on a large-mode-area Er:ZBLAN fiber. Reliable self-starting mode-locking is achieved via the combination of nonlinear polarization rotation and a semiconductor saturable absorber. Stable mode-locked pulses with a pulse energy of 9.4 nJ and a pulse duration of 325 fs are generated. To the best of our knowledge, this is the highest pulse energy directly generated from a femtosecond mode-locked fluoride fiber laser (MLFFL) to date. The measured M2 factors are below 1.13, indicating a nearly diffraction-limited beam quality. Demonstration of this laser provides a feasible scheme for the pulse energy scaling of mid-infrared MLFFLs. Moreover, a peculiar multi-soliton mode-locking state is also observed, in which the time interval between the solitons varies irregularly from tens of picoseconds to several nanoseconds.

Tunable and switchable single-/dual-wavelength Er-doped hybrid mode-locked fiber laser by dual-PMFs Lyot filter

Tunable and switchable single-/dual-wavelength Er-doped hybrid mode-locked fiber laser by dual-PMFs Lyot filter

Numerical analysis of hybrid mode-locking stability in a Ho-doped fiber laser.

We numerically study a hybrid mode-locked holmium-doped fiber laser based on the coupled nonlinear Schrödinger equations, by introducing nonlinear polarization rotation and saturable absorber in a same cavity. Maps of mode-locking states related to the intracavity wave-plates are created to evaluate the stability of mode-locking. Nonlinear polarization rotation imposes negative effect of linear absorption and even reverse saturable absorption to the pulses in the hybrid cavity. Saturable absorber compensates the negative effect from nonlinear polarization rotation, then consequently contributes to the stability of single-pulse mode-locking states. The extension of pulse time duration indicates the dynamic synergy between nonlinear polarization rotation and saturable absorber rather than the static combination mechanism of them.

Switching and coexistence of stretched pulse and dissipative soliton in a hybrid mode-locked fiber laser

We experimentally demonstrate a thulium–holmium co-doped hybrid mode-locked fiber laser, which can operate in two modes. One is the switch between stretched pulse and dissipative soliton, the other is the dual-wavelength mode-locking corresponding to the coexistence of stretched pulse and dissipative soliton. The optical spectra of the stable dual-wavelength mode-locking pulses centers at 1905 nm and 1946 nm respectively, and the corresponding pulse widths are 5.9 ps and 823 fs. In addition, the central wavelength is in the tunable range of 27 nm when the laser operates on a dissipative soliton regime.

Saturable absorber based on graphene for a hybrid passive mode-locked erbium-doped fiber laser

We proposed a hybrid passive mode-locked fiber laser based on a saturable absorber fabricated by coating a layer of graphene on a single-mode fiber with inscribed short waveguides. The hybrid mode-locked fiber laser operation is achieved by use of nonlinear polarization rotation and saturable absorption. The output pulses have the center wavelength of 1558 nm, 3-dB bandwidth of 4.6 nm, pulse width of 605 fs, repetition frequency of 20.8 MHz, and signal-to-noise ratio of 60 dB. Compared with the use of nonlinear polarization rotation mode locking alone, the pulse width is compressed by 211 fs, and the signal-to-noise ratio is improved by 5 dB. The advantages of hybrid mode locking mechanism include simple structure and convenient operation, which make the system attractive in ultrafast lasers.

Switching and Coexistence of Stretched Pulse and Dissipative Soliton in a Hybrid Mode-Locked Fiber Laser

Switching and Coexistence of Stretched Pulse and Dissipative Soliton in a Hybrid Mode-Locked Fiber Laser

Tunable and Switchable Single/Dual-Wavelength Er-Doped Hybrid Mode-Locked Fiber Laser with Dual-Pmfs Lyot Filter

Tunable and Switchable Single/Dual-Wavelength Er-Doped Hybrid Mode-Locked Fiber Laser with Dual-Pmfs Lyot Filter

Numerical study of a hybrid mode-locked erbium-doped fluoride fiber laser at 2.8 μm

We numerically investigate a hybrid mode-locked erbium-doped fluoride fiber laser in the mid-infrared region. Based on the coaction of nonlinear polarization rotation (NPR) and semiconductor saturable absorber mirror (SESAM), uniform mode-locked soliton pulse with 155 fs pulse duration, 14.78 kW peak power, and 2.29 nJ pulse energy can be achieved. For comparison, the single SESAM mode-locking and NPR mode-locking of the erbium-doped fluoride fiber laser are simulated, respectively. The effect of all kinds of parameters including gain fiber length, saturable energy of the gain fiber, linear cavity phase delay bias, and small-signal gain on the hybrid mode-locking laser are also investigated.

10GHz regeneratively mode-locked erbium-doped fiber laser combined with nonlinear amplifying loop mirror

Mode-locked fiber lasers can generate short pulses with a high repetition rate. It can be used in nonlinear optical imaging, photo-communication and other fields. Obtaining narrow pulses with high repetition frequency has become a hot research topic. In this article, we demonstrate a hybrid mode-locked fiber laser, which is a regeneratively mode-locked erbium fiber laser operating at 10 GHz, incorporating a nonlinear amplifying loop mirror to generate a 1.9 ps pulse sequence. This all-fiber laser with a high-repetition-rate and short pulses has the advantages of high stability and self-starting, which has a wide range of applications.