Mode-locked Soliton Fiber Laser Research Articles

Generation of vector soliton mode-locked Er-doped fiber laser using ZrTe2 as saturable absorber

We demonstrate a passively mode-locked fiber laser employing zirconium telluride (ZrTe2) as saturable absorber and illustrate its application for vector soliton generation in erbium-doped fiber lasers. By tuning the pump power and polarization controller, stable mode-locked operations in different operations are obtained with different cavity lengths. In addition, we also further research on characteristics of the vector solitons formed in fiber laser. The vector features of the obtained solitons are experimentally explored, and these solitons are proved to be group velocity locked vector solitons. Our research results indicate that ZrTe2 nanosheets could be available saturable absorber for ultrashort pulse fiber lasers, especially for generating vector soliton pulses in fiber lasers.

Soliton and bound-state soliton mode-locked fiber laser based on polarization-dependent grating.

We demonstrate the generation of solitons and bound-state solitons in a passively mode-locked fiber laser based on the nonlinear polarization rotation effect by polarization-dependent helical grating. The CO2-laser-inscribed grating has a high polarization-dependent loss of 24.4 dB at 1558.4 nm, which has facilitated the achievement of stable mode locking. The soliton laser could generate 548.9 fs pulses at 1560.59 nm with a spectrum bandwidth of 5.45 nm and a signal-to-noise ratio of 75.2 dB. Through adjustment of the polarization controller and pump power, a bound-state soliton mode-locked pulse with a spectral modulation period of 3.11 nm was achieved and the temporal interval between the two solitons was 2.19 ps. Furthermore, its repetition rate can be easily manipulated by varying the pump power. The results indicated that the polarization-dependent helical grating is an excellent polarizer that could be applied in an ultrafast fiber laser.

Morphology effect of zinc oxide on nonlinear optical properties for soliton mode-locked fiber laser

In this work, zinc oxide (ZnO) with different morphologies was synthesized to examine the effect of morphology on the nonlinear optical properties. The impact of this effect on the performance of mode-locked pulsed fiber laser was further investigated. The ZnO particle-like and flake-like were prepared using the sol-gel and hydrothermal methods. The twin detection technique explored the nonlinear optical properties of both ZnO samples. The ZnO flake-like sample exhibited higher modulation depth and saturation intensity and lower non-saturable loss than the ZnO particle-like sample. Consequently, the 1.9 μm mode-locked pulsed fiber laser generated by utilizing the ZnO flake-like based saturable absorber (SA) has demonstrated a better performance relative to its short pulse width, high SNR value, high pulse energy, and high efficiency. The results of this work could give a valuable guideline for selecting the appropriate nanomaterial-based SA for various photonics applications.

CsxWO3 nanorods with broadband nonlinear response for Q-switched and mode-locked pulse generation

Nano-CsxWO3 with broadband local surface plasmon resonance is the promising candidate for nonlinear photonics applications. In this work, Q-switched and mode-locked pulses were generated from Er- and Tm- doped fiber lasers by using CsxWO3 nanorods (NRs) as saturable absorbers (SAs). The CsxWO3 NRs were synthesized by a water controlled-release solvothermal process. Then they were mixed with sodium carboxymethylcellulose (NaCMC) solution to fabricate a SA film and deposited onto a d-shaped fiber to fabricate a d-shaped fiber SA. These SAs exhibited excellent nonlinear optical properties at 1.5- μm and 2- μm. A ∼ 1560 nm Q-switched fiber laser with the shortest pulse width of 3.8 µs, the maximum average power of 10 mW, a pulse energy of 0.35 μJ was obtained by using the filmy CsxWO3 SA. A stable soliton mode-locked fiber laser at ∼ 1943 nm was realized based on the d-shape fiber CsxWO3 SA, it had a maximum average output power of ∼ 50 mW, a pulse duration of ∼ 292 fs, and a repetition rate of 25.5 MHz. Our results show that the CsxWO3 NRs are potential nonlinear materials for broadband ultrafast response and Q-switched/mode-locked pulse generation.

Ultra-Broadband NPE-Based Femtosecond Fiber Laser

A dissipative soliton mode-locked Yb-doped fiber laser is investigated experimentally and numerically from the point of view of generating ultra-broadband ultrashort pulses. An energy up to 2.2 nJ and a spectral bandwidth over 60 nm (at the −10 dB level) were obtained experimentally without dispersion compensation in the cavity. Almost a 100-fold compression coefficient has been achieved, so the resulting pulse duration was 149 fs. The numerical simulation has shown that a further scaling up to 3.5 nJ and a 100 nm spectral bandwidth is possible by reducing the low power transmission coefficient of the NPE-based SAM and increasing the amplification. At the same time, the tolerance of the SAM to a low power radiation is responsible for the transition to a multi-pulse operation regime.

Single crystalline BiOCl nanosheets with oxygen vacancies for ultrafast mode-locking operation

In this work, we synthesized the single-crystalline square BiOCl nanosheets with oxygen vacancies via the facile solvothermal route. The prepared BiOCl nanosheets were deposited on a tapered microfiber as a saturable absorber. Via the evanescent filed interaction with the BiOCl saturable absorber, a soliton mode-locked Er-doped fiber laser was demonstrated for the first time, producing a pulse duration of 990 fs at a central wavelength of 1563 nm with a FWHM bandwidth of 3.2 nm. The signal-to-noise ratio was 36 dB at the fundamental repetition rate of 7.9 MHz. Our results confirmed that the BiOCl nanosheets with abundant oxygen vacancies could be applied for the ultrafast photonics.

Observation of soliton and bound soliton in erbium-doped fiber lasers using single-walled carbon nanotubes mode-lockers under gamma irradiation

This study looked into the generation of soliton and bound-state soliton passively mode-locked Erbium-doped fiber lasers (EDFLs) using gamma (γ) ray irradiated single-walled carbon nanotubes-poly(ethylene oxide) (SWCNT-PEO) film as a saturable absorber (SA). Using the liquid phase exfoliation method, a free-standing SWCNT-PEO film-based SA was developed. The SWCNT-PEO film was non-irradiated before being integrated into the laser cavity, and then subjected to a series of low dose radiations of 50 Gy, 100 Gy, and 200 Gy. The non-irradiated film generated a soliton mode-locked pulsed fiber laser operating at 1560 nm, with a repetition rate of 23.8 MHz and a pulse width of 0.60 ps. Irradiated films of 50 Gy and 100 Gy produced bound-state solitons with pulse separations of 7.68 ps and 2.62 ps, respectively. A soliton mode-locked pulsed fiber laser with an operating wavelength of 1556 nm and a pulse width of 0.59 ps is produced for the 200 Gy irradiated film.

Combined influence of the gain and dispersion of a mode-locked fiber laser on a time-stretching analog-to-digital conversion link.

Using theory and experiments, we demonstrated the combined influence of the spectral gain and dispersion of a dissipative soliton mode-locked fiber laser on a time-stretching analog-to-digital conversion link without an optical amplifier. The theoretical and experimental results indicate the following: first, the amplitude and envelope shape of the stretched signal are mainly affected by the spectral gain of the dissipative soliton at different central wavelengths under a radio frequency signal of 10 GHz. Second, at the higher frequency of 25 GHz, the influence of the phase shift induced by the dispersion of different spectral ranges on the amplitude of the stretched signal becomes clearer. The amplitude of the stretched signal across all spectral ranges decrease, and the envelope shape differs from that at 10 GHz. Moreover, the wavelength at the maximum amplitude of the stretched signal changes, for which the influence of the spectral dispersion is greater than that of the spectral gain. Finally, the ratio of the amplitude at 25 GHz to that at 10 GHz at different spectral ranges are different, which indicates that the amplitude of the stretched signal at different spectral ranges is affected by the phase shift by different degrees.

Antimonene-based saturable absorber for a soliton mode-locked and Q-switched fiber laser in the 2 μm wavelength region

We demonstrate antimonene as a saturable absorber (SA) to generate an ultrafast mode-locked and Q-switched laser in the 2 μm wavelength region. The two antimonene-based SAs were prepared and inserted separately in a thulium–holmium-doped fiber laser to produce the pulsed laser. Antimonene was coated onto a tapered fiber to generate soliton mode-locked pulses and used in thin-film form for the generation of Q-switched pulses. The mode-locking was stable within a pump power of 267 mW–511 mW, and the laser operated at a central wavelength of 1897.4 nm. The mode-locked laser had a pulse width of 1.3 ps and a repetition rate of 12.6 MHz, with a signal-to-noise ratio of 64 dB. Q-switched laser operation was stable at a wavelength of 1890.1 nm within a pump power of 312 mW–381 mW. With the increase in pump power from 312 mW to 381 mW, the repetition rate increased to a maximum of 56.63 kHz and the pulse width decreased to a minimum value of 2.85 μs. Wide-range tunability of the Q-switched laser was also realized within the wavelength range of 1882 nm–1936 nm.

Direct observation of the build-up and extinction of similaritons in an all-normal dispersion fiber laser

Similaritons have attracted considerable attention thanks to their outstanding output performance in recent years. In this paper, we explored the entire dynamic evolution process of similaritons in an all-normal dispersion fiber laser through the time-stretch dispersive Fourier transform technique. Particularly, the narrow-band spectral filtering effect on the pulse evolution dynamics has been discovered. The “memory” ability in the relaxation oscillation state has disappeared in similariton fiber lasers compared with the traditional soliton mode-locked fiber lasers, and the build-up time is much shorter than other fiber lasers mode-locked by the nonlinear polarization evolution. Furthermore, the extinction process of the similariton fiber laser is observed and evaluated for the first time as well. An unstable time period accompanied by a high spectral peak over the spectrum is captured during the extinction process, and then the damped relaxation oscillation state is observed. These results can provide new perspectives into the ultrafast transient process of similaritons in all-normal dispersion fiber lasers and the dynamics of sophisticated nonlinear systems.

Raman-enhanced multicolor pulses in dissipative soliton mode-locked ring-cavity fiber laser based on GIMF-SA

The stable multicolor complex with dissipative solitons (DS) and Raman pulses (RP) is experimentally demonstrated in the mode-locked Yb-doped ring-cavity fiber laser based on a graded-index multimode fiber (GIMF) as a saturable absorber (SA). The central wavelength of DS and RP are 1032.01 nm and 1078.08 nm, respectively. By wavelength-dividing the output pulse, it is found that the pulse width and period of DS and RP are consistent with the total pulse, but the DS pulse intensity is larger than that of RP. The single-to-noise ratio (SNR) of DS is about 55 dB, which is large than that of the complex pulse. We further improve the stability of the mode-locked state in the cavity by separating the RP out of the cavity. The experimental results obtained by two methods of separating pulses indicates that the stimulated Raman scattering (SRS) effect destabilizes the DS mode-locked fiber laser and doesn’t disrupt the single pulse generation regime.

Enhanced optical nonlinearity and ultrafast carrier dynamics of TiO2/CuO nanocomposites

Transition metal oxides (TMOs) are drawing multitudinous interest due to their strong thermochemical stability. In the present work, we proposed a facile strategy to fabricate TiO 2 /CuO nanocomposites. By using the conventional open- and closed-aperture Z-scan technology, the eminent nonlinear optical (NLO) properties of the as-prepared TiO 2 /CuO nanocomposites were demonstrated. In order to deeply investigate the NLO enhancement mechanism, we established a theoretical model to study the photogenerated carriers transfer dynamics at the interface with rate equations and the fouth-order Runge-Kutta algorithm. The simulation results indicated that under pumping irradiation, the carriers transferring from CuO to TiO 2 promoted the nonlinear optical absorption of CuO nanosheets and increased the modulation depth. Experimentally, the transient absorption spectroscopy and broadband time-resolved pump-probe measurements were presented to study the role of the carrier dynamics in the broadband near-infrared region. To further confirm the enhanced NLO response in TiO 2 /CuO nanocomposites, a highly stable dissipative soliton mode-locked Yb-doped fiber laser with TiO 2 /CuO saturable absorber was constructed at 1 μm for the first time. Our work manifested the key effects of the interface in TiO 2 /CuO nanocomposites to boost the NLO features which can be applied in ultrafast photonics applications.

Deposition of Ti2AlC MAX phase onto the side polished fiber as saturable absorber for soliton mode-locked fiber laser generation

Deposition of Ti2AlC MAX phase onto the side polished fiber as saturable absorber for soliton mode-locked fiber laser generation

Dispersion Management and Pulse Characterization of Graphene-Based Soliton Mode-Locked Fiber Lasers

This paper presents the generation and characterization of femtosecond pulses utilizing graphene-polymethyl-methacrylate (PMMA) thin-film saturable absorber (SA), which is subjected to different lengths of single-mode fiber (SMF) in an erbium-doped fiber laser cavity. The graphene/PMMA-SA is prepared by using a simple transfer procedure of the thin-film on a fiber ferrule. By increasing the SMF length from 0 to 4 m, the corresponding group velocity dispersion of the entire cavity is estimated to change from −0.033 to −0.121 ps2. Analysis of the pulse performance shows that the pulse width behavior varies from 820 fs to 710 fs against different cavity lengths. Similarly, the pulse repetition rate and the spectral bandwidth can be adjusted from 12.5 to 10.0 MHz, and from 8.2 to 5.6 nm, respectively. A comprehensive discussion on the pulse performance is presented, which can contribute to widening the knowledge on the operation of graphene-based soliton mode-locked erbium-doped fiber lasers based on dispersion management by controlling the cavity length.

All-fiber [formula omitted]m band tunable continuous-wave and soliton mode-locked Ho-doped fiber laser

We report the design and performance of a 2.1μm tunable holmium-doped fiber laser (HDFL) in both continuous-wave (CW) and mode-locked regime. Nonlinear polarization rotation (NPR) mechanism is used as a saturable absorber to realize the evolution from CW to mode-locked state. Another function of NPR mechanism is to realize wavelength tuning as a wavelength selection device. The tunable single-wavelength CW laser can be tuned from 2039 nm to 2118 nm. In addition, conventional soliton operation is obtained with the wavelength range of 2049.2–2087.3 nm.

Single- and bound-state soliton mode-locked Er-doped fiber laser based on graphene/WS2 nanocomposites saturable absorber

We report a passively mode-locked Er-doped fiber laser based on WS2, graphene, and graphene/WS2 (G/WS2) nanocomposites saturable absorber (SA), respectively. These materials were easily prepared by liquid phase epitaxy (LPE) method with isopropanol (IPA). Compared with pure graphene or pure WS2, the film of G/WS2 nanocomposites possesses low nonsaturable loss (31%) and low saturable intensity (12.78 MW/cm2), which is of benefit to achieve passive mode-locked fiber laser. Stable traditional soliton pulses were generated with central wavelength of 1566.7 nm, spectral width of 7.3 nm, pulse duration of 357 fs, and repetition rate of 22.86 MHz. Further, we present the bound-state soliton mode-locked based on G/WS2-SA with a modulation period of 4.9 nm, soliton spacing of 1.67 ps and pulse width of 353 fs. Our work extends the studies for G/WS2 nanocomposites in ultrafast photonics applications.

Co3O4 film saturable absorber for generating soliton mode-locked pulses in erbium-doped fiber laser

Herein, a soliton mode-locked erbium-doped fiber laser is proposed for the 1.5-μm region using Co3O4 as a saturable absorber (SA). Spherical Co3O4 nanoparticles (NPs) were embedded in polyvinyl alcohol to form a Co3O4- polyvinyl alcohol (PVA) film. Highly stable soliton mode-locked pulses based on the Co3O4-PVA film output were observed at 1558.86 nm with a 3 dB bandwidth, fundamental frequency, pulse width, and signal-to-noise ratio of 2.25 nm, 5.68 MHz, 1.24 ps, and 72.37 dB, respectively. Our experimental results demonstrate that the spherical Co3O4 NPs exhibited good performance in creating soliton mode-locked fiber lasers as a promising SA.

Wavelength-tunable picosecond laser source based on filtering and amplifying broadband dissipative soliton pulse

A method for obtaining picosecond pulse sources with continuously tunable central wavelengths is demonstrated numerically and experimentally. A dissipative soliton (DS) mode-locked erbium-doped fiber (EDF) laser based on the nonlinear polarization rotation provides the seed pulse with a flat-top spectral profile and a 55 nm spectral bandwidth. Then it is filtered by a wavelength-tunable super-Gaussian bandpass filter and amplified by two segments of EDFs with different doping concentrations. The output DS pulse from the EDF laser can be compressed from 5.532 ps to 0.291 ps by using a single-mode fiber (SMF-28e), while the pulse energy is about 1.6 nJ. Furthermore, the about 4 ps and 6.84 nJ pulses with continuously tunable central wavelengths ranging from 1535 to 1580 nm can be obtained by amplifying the spectrally filtered pulses. The tunable picosecond pulse source based on the extra-cavity filtering method is very useful for many practical applications because of its flexible wavelength control.

Experimental revealing of fiber laser soliton build-up activated by shaking-soliton triplets

Optimization of self-starting in passively mode-locked optical soliton fiber laser resonators results from a complex transient dynamic involving soliton molecules, soliton-based complexes and supramolecular structures, with particle-like properties. By means of time-stretch dispersive Fourier transform based real-time spectroscopy, we identify a new route to the passive mode-locking of fiber laser solitons. A raised relaxation oscillation stage is followed by the generation of shaking-soliton molecular triplets. The relative phase between satellite and main pulses of shaking soliton triplets evolves chaotically, while the two satellite pulses are orthogonal to each other in their state of polarization. These results provide new perspectives into the soliton formation and the internal dynamics of soliton molecules with higher degrees of freedom.

Single-shot method to study high order solitons in all-polarization-maintaining soliton mode-locked fiber lasers.

A single-shot experimental method is proposed to study non-repetitive evolutions of high order solitons. In our experiments, high order solitons are prepared in the building up process of a soliton fiber laser, and the order of high order soliton is controlled via changing the parameters of the laser. The evolution of high order soliton is recorded by the single-shot spectral measurements-time stretch dispersive Fourier transform. A 4th order soliton evolution under perturbations of gain saturation and saturable loss is studied, showing how a leading pulse wins the competition against the tailing one. Our work provides a controllable technique to study the high order solitons evolutions, which can be applied in the research of ultrafast laser amplifications and supercontinuum generations.