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Thulium-doped fiber lasers (TDFLs) operating at 1.7 μm have immense potential for multiphoton microscopy and imaging applications. However, further research and development are needed, particularly in the ultra-short wavelength range below 1720 nm. Herein, we demonstrate the mode-locked TDFL at 1.7 μm, utilizing a microfiber InSb saturable absorber. By employing intracavity filters, optimizing the gain fiber length, and incorporating a broadband evanescent field absorber, we achieve high-performance ultra-short wavelength solitons in the TDFL. The solitons exhibit a central wavelength of 1707 nm, a pulse width of 895 fs, a repetition rate of 23.36 MHz, and a single pulse energy of 1.7 nJ. Moreover, our experiments demonstrate the generation of diverse soliton states, including high-order harmonic and bound solitons. We also explore the dynamics of mode-locking through experimental investigations. Our findings establish a solid foundation for the research and control of diverse 1.7 μm mode-locked operation state, advancing the field of ultrafast fiber lasers in this wavelength band. [ABSTRACT FROM AUTHOR]

Noise‐like pulses (NLPs) are becoming increasingly attractive for a variety of applications such as supercontinuum generation, materials processing, and low‐coherence spectral interferometry. Related research in the near‐infrared region is extensive, yet few studies have been reported in the mid‐infrared (MIR) region. Herein, a systematic investigation of MIR NLPs is made for the first time. An approach is presented by exploiting a polarization‐maintaining fluoride fiber in the mode‐locked oscillator to cause a polarization‐dependent delay between the orthogonal‐polarized components of intracavity circulating pulses, thus generating a series of ultrashort pulses which will eventually form a stable wave packet, namely, NLP. Numerical simulations based on the extended coupled nonlinear Schrödinger equations predict the generation of NLPs, and reveal key aspects of the pulse evolution. Experiments yield linearly polarized NLPs at 2.8 μm with a maximum average power of 498 mW and a spike width of 4.3 ps, corresponding to a pulse energy of 12 nJ. The experimental results are in good agreement with the simulation results. This work constitutes a major step toward the development of MIR ultrafast fiber lasers with NLPs output. [ABSTRACT FROM AUTHOR]

We demonstrate broadband mid-infrared supercontinuum generation in a piece of indium fluoride fiber pumped by an ultralow repetition rate noise-like pulse mode-locked fiber laser. This figure-9 mode-locked Tm-doped fiber laser has a long laser cavity by inserting a piece of standard single mode fiber and a piece of dispersion compensation fiber, which delivers mode-locked noise-like pulse with a repetition rate of ∼190 kHz. The mode-locked noise-like pulse train has a low pulse duty cycle of 4.38 × 10−4. With only one Tm-doped fiber amplifier, the ultra-low repetition rate noise-like pulse is amplified to ∼3 W. The pulse energy is boosted to ∼15 μJ with a peak power of ∼6.5 kW. Pumping a piece of highly nonlinear indium fluoride fiber with the amplified noise-like pulse, a flat mid-infrared supercontinuum with a covering range from ∼1500 nm to ∼4100 nm can be achieved. Due to the low operational power, no cooling installations are required to control the temperature of the supercontinuum laser system. This all-fiber mid-infrared SC laser source has a relatively simple architecture and low cost. This study demonstrates the great advantages of this type of ultra-low repetition rate noise-like pulses in mid-infrared supercontinuum generation. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials show great promise as saturable absorbers (SAs) for ultrafast fiber lasers. However, the relatively low modulation depth and poor stability of some 2D materials, such as graphene and black phosphorus, restrict their applications in the mid-infrared pulse generation. Herein, we first report a novel 2D double transition metal carbide, denoted as Mo2Ti2C3Tx MXene, as the saturable absorber (SA) for a passively Q-switched mid-infrared fiber laser. Due to the unique four-metal atomic layer structure, the Mo2Ti2C3Tx exhibits superior saturable absorption properties, particularly with a higher modulation depth (40% at 2796 nm) than most of the other reported 2D SA materials. After incorporating the MXene SA with an erbium-doped fiber system, the passively Q-switched pulses were achieved with a repetition rate of 157.3 kHz, the shortest pulse width of 370 ns, and single-pulse energy of 1.92 μJ, respectively. Such results extend the MXene-based SAs as promising candidates for advanced photonic devices. [ABSTRACT FROM AUTHOR]

We propose and experimentally demonstrate a novel switchable quadruple-wavelength CW erbium-doped fiber laser, using a linear cavity structure. It is composed of two Sagnac loops that act as cavity mirrors in the resonant cavity. The left loop consists of a 3 dB fiber coupler (FC), a squeezed polarization controller (PC), and a chirped fiber grating. The right loop consists of a 10 dB FC, the same PC and a length multimode fiber with a core diameter of 62.5 μm. The two loops based on different operation principles become two comb filters to jointly excite the multiwavelength output. On the role of the polarization hole burning effect, after adjusting the two PCs, the laser can switch flexibly to output fourteen kinds of different modes from a single wavelength to the quadruple wavelength. All lasing lines, with a narrow linewidth less than 0.28 nm, have the optical signal-to-noise ratio of more than 20 dB. The laser with good power uniformity shows better stabilities of the wavelength and peak power. [ABSTRACT FROM AUTHOR]

A 1/1.5 μm dual-band mode-locked fiber laser is experimentally demonstrated. The laser is based upon an architecture in which the 1 μm and the 1.5 μm signals are generated in independent cavities that share the identical active fiber. The mode-locking of the 1 μm laser is realized via nonlinear polarization evolution (NPE), whilst the 1.5 μm laser is mode-locked through cross-phase modulation (XPM) induced by the 1 μm laser and the mode-locking is further stabilized by NPE. Synchronized dual-band mode-locking operation is achieved using the laser. [ABSTRACT FROM AUTHOR]

Two-dimensional materials with a sheet structure have excellent optical, electrical and mechanical properties, and have attracted much attention in recent years, especially In2Se3 (the N-type semiconductor compound), which has a rapid development in the fields of materials science and optical communication. In this paper, the nonlinear saturation absorption characteristics of In2Se3 are studied. The In2Se3 nanosheet dispersion can be used in ultrafast photonics applications. The nonlinear absorption is measured by power dependent method, and the modulation depth and saturation intensity are 3.8% and 246.6 MW cm−2, respectively. More importantly, In2Se3 is used as a saturable absorber (SA) in a passively mode-locked erbium-doped fiber laser. The proposed mode-locked fiber laser is demenstrated with a center wavelength of 1529.4 nm, a fundamental frequency of 5.9 MHz, a spectral width of 3.96 nm, a pulse width of 1.38 ps, and a signal-to-noise ratio of 55 dB. For the first time, harmonic mode-locking with a high-repetition rate of 431 MHz is achieved when the pump power is 360 mW corresponding to 73rd-order harmonic mode locking. It can be seen that In2Se3 is indeed a new excellent photonic material, which can be used in fiber optic communication, SAs photonics, laser material processing and light modulators. [ABSTRACT FROM AUTHOR]

We demonstrate the HfSe2 saturable absorber (SA) for the generation of ultrafast pulse laser. The HfSe2 SA device is fabricated by integrating HfSe2 nanosheets (NSs) with a microfiber. The material and optical characteristics of HfSe2 NSs show their high quality. The nonlinear optical absorption of HfSe2 SA is measured with a modulation depth of 5.8%. Stable soliton mode-locked laser based on HfSe2 SA is realized at the central wavelength of 1561.43 nm with pulse duration of 297 fs and the maximum pulse energy of 2.68 nJ. Our soliton fiber laser has a maximum output power of 48.5 mW with a high slope efficiency of 12.8%, which indicate that HfSe2 is a good candidate of SA for high efficient ultrashort pulses generation. [ABSTRACT FROM AUTHOR]

Two-dimensional layered materials have been widely utilized as nonlinear absorption materials to transfer continue-wave into pulse trains in fiber laser systems. Here, we prepare robust GaSe/GeSe composites with high power bearing capacity as saturable absorbers (SAs) and then investigate their nonlinear optical properties via broadband Z-scan measurement at 800 nm and 1550 nm, respectively. The modulation depths of GaSe/GeSe based SAs are measured to be 11.97% and 7.69% at 1550 nm. After incorporating the GaSe/GeSe SAs into an Erbium-doped fiber laser cavity, passively Q-switched pulse trains could be obtained with repetition rates changing from 83.58 to 136.78 kHz (70.41 to 161.65 kHz). The maximum output power and pulse energy are 52.1 mW/370.67 nJ (GaSe) and 21.6 mW/133.74 nJ (GeSe) under the maximum pump power of 600 mW. The results indicate that GaSe and GeSe possess outstanding thermal stability and could be employed as remarkable saturable absorption materials for high-energy pulses generation. [ABSTRACT FROM AUTHOR]

We demonstrate a compact all-fiber Er-doped chirped pulse amplification (CPA) system that can produce ∼344 fs pulses with an average power of up to 1.02 W and a repetition rate of 40.6 MHz at 1.56 μm (corresponding to an energy of 25.1 nJ). The pulse compressor in the CPA system is based on a hollow core photonic crystal fiber which is directly butt-coupled to the silica fiber. A mismatched negative third-order dispersion is used to compensate the accumulated nonlinear phase shift in the amplification process for the first time, resulting in the generation of sub-400 fs pulses from an all-fiber Watt-level Er-doped CPA system. Our system architecture offers a possibility for ultrashort pulse generation from all-fiber Er-doped CPA lasers. [ABSTRACT FROM AUTHOR]

Despite extensive applications ranging from optoelectronic devices to flexible devices, two-dimensional layered materials used as ultrafast optical modulation materials have suffered from limited operation wavebands due to their intrinsic bandgap. Here, we investigate the nonlinear optical (NLO) response of group IIIA/IVA monochalcogenides XTe (X = Ga and Ge), which exhibit a remarkable saturable absorption response at a broadband wavelength. By using a liquid phase exfoliation technique, we prepare XTe nanosheets with few-layer thickness in a deionized water solvent and investigate their NLO responses at 800 nm, 1.5 µm, and 2 µm, respectively. Both GaTe and GeTe nanosheets exhibit ultrafast saturable absorption at 800 nm with 32.4 μJ (48.4 µJ) incident intensity. After preparing microfiber-based nanosheet optical modulators, their saturable absorptions are measured at 1.5 µm and 2 µm. The GaTe-SA possesses a little bit higher modulation depth (42.3% at 1.5 µm/30.7% at 2 µm) than the GeTe-SA (30.5% at 1.5 µm/8.3% at 2 µm) at two wavelengths. The lifetime of GaTe and GeTe nanosheets is measured to be 2.8 ps and 3.3 ps, respectively. In addition, we further examine their saturable absorption via incorporating them into an erbium- and a thulium-doped fiber laser system and obtain stably passively mode-locked pulse trains, respectively. The distinct NLO properties indicate a large potential of XTe nanosheets in the development of an ultrafast optical mode locker with a wideband operation wavelength. [ABSTRACT FROM AUTHOR]

A wavelength-tunable passively-synchronized 1-μm Q-switched and 1.5-μm gain-switched dual-wavelength pulsed fiber laser has been demonstrated with a single gain fiber for the first time to our knowledge. The realized dual-wavelength co-oscillation is based on a dual ring-cavity configuration with a common Er/Yb co-doped fiber (EYDF). The Q-switched 1-μm pulses are generated through the saturable absorption effect of unpumped EYDF aided by a 1.5-μm oscillation cavity, whereas the 1.5-μm pulses are produced by the gain-switching of Er3+ ions induced by the 1-μm Q-switched pulses. A tuning range of 11.7 nm from 1045.3 to 1057 nm and 29.7 nm from 1535 to 1564.7 nm are obtained at stable synchronized pulse operation for 1 and 1.5-μm spectral bands, respectively. [ABSTRACT FROM PUBLISHER]

We demonstrate a simple Fe3O4 nanoparticles (FONPs) based Q-switched fiber laser that is able to generate stable nanosecond pulses with single-wavelength or multiwavelength regimes. In the single-wavelength lasing scheme, the fiber laser generates 613-ns pulse with average output power of 41.2 mW, pulse energy of 321.3 nJ, and signal-noise-ratio of 54.4 dB. In the multiwavelength lasing scheme, stable pulse is achieved with 18-wavelength channels contained within the 3-dB bandwidth range. Our results prove that the FONPs can act as an effective Q-switch for high-energy pulse generation. [ABSTRACT FROM PUBLISHER]

We investigate on a multi-wavelength operation erbium-doped fiber laser Q-switched by a graphene-based saturable absorber. Stable pulses were generated with the widths from 6.9 to 1.5 µs, energies from 40.4 to 130.2 nJ and repetition rates from 68.32 to 132.9 kHz, when the pump power increased from 142.32 to 441.86 mW. A fiber Bragg grating with five reflective peaks was inserted into the fiber ring through an optical circulator, resulting in a stable output of five-lasing-wavelength output. The laser can perform as a low-cost and easy-built all fiber light source, and has potential applications in the fields where pulses at multi-wavelength operation are needed, i.e., temperature or strain fiber sensors. [ABSTRACT FROM AUTHOR]

In this study, a graphene and optical microfiber coupler (OMC) integrated device (GOMC) was proposed and fabricated. After its characteristic analysis and testing, it was applied to the development of adjustable multi-wavelength fiber lasers. By integrating the OMC with graphene, the polarization dependence of OMC was enhanced. Meanwhile, the novel GOMC was given the capabilities of filtering, coupling, beam splitting, and polarization correlation. When the GOMC was integrated as a filter and beam splitter into the ring cavity of the fiber laser, the proposed GOMC-based fiber laser could achieve single-wavelength and multi-wavelength regulated output. The laser had a 3 dB linewidth of less than 30 pm, a signal-to-noise ratio of approximately 40 dB, and an output power fluctuation of less than 1 dB. The GOMC could also be used for the development of functional devices, such as adjustable mode lockers and mode coupling selectors, which provide an excellent experimental platform for new fiber lasers and the research of multi-dimensional light-field manipulation. [ABSTRACT FROM AUTHOR]

High‐power all‐fiber thulium lasers have gained considerable interest in recent times due to their distinct characteristics and versatile applications in the medical and industrial sectors. This review article presents a comprehensive examination of the advancements and challenges in this field. It begins with an overview of thulium‐doped silica fiber, which is a critical component for high‐power lasers operating at the 2 µm (micrometer) wavelength band. The research progress of essential high‐power thulium laser sources, including continuous‐wave (CW), quasi‐continuous wave (QCW), and pulsed lasers, is then thoroughly analyzed, highlighting their respective strengths and limitations. Additionally, the diverse applications of high‐power thulium fiber lasers in medical and industrial domains are summarized. Furthermore, the article emphasizes the current challenges in the advancement of high‐power thulium‐doped fiber lasers (TDFLs) and outlines potential avenues for future development. Despite TDFLs being the predominant laser source in lithotripsy and material processing applications, optimizing their performance and expediting further progress in thulium laser technology remain crucial objectives. This review article aims to provide valuable insights for researchers, engineers, and professionals working in the field of high‐power fiber lasers operating at 2 µm. [ABSTRACT FROM AUTHOR]

A novel saturable absorber (SA) was fabricated by coating the topological insulator (TI) film on microfiber using pulsed laser deposition (PLD) method. The TISA device had an insertion loss of ~1.25 dB, a saturable intensity of 26.7 MW/cm2, a modulation depth of ~5.7%, and a nonsaturable loss of 20.5%. Upon employing this SA device, we established a passively mode-locked EDFL and achieved nearly free-chirped soliton pulse with 286 fs of pulse duration and >73 dB of signal to noise ratio (SNR). This result clearly evidences that the PLD is an effective scheme for practical SA device fabrication. [ABSTRACT FROM AUTHOR]

• A pulse-state switchable mode-locked Tm-doped fiber laser based on linear-cavity nonlinear polarization rotation is proposed. • Seamless transitions between conventional soliton, multiple-pulse, and noise-like pulse states are achieved. • Provides a solution for pulse-state switchable mode-locking in all-fiber thulium-doped lasers. We present an experimental demonstration of a pulse-state switchable Tm-doped fiber laser, mode-locked using linear-cavity nonlinear polarization rotation (LNPR). Compared to previous LNPR lasers with free-space structures, our laser cavity employs an all-fiber design, which enhances the laser flexibility. The laser operates in three states within a large anomalous dispersion, including conventional soliton, multi-pulse, and noise-like pulse states. This research provides an effective solution for realizing a multifunctional Tm-doped fiber laser with a simple and stable configuration, making it both appealing and promising for various practical applications. [ABSTRACT FROM AUTHOR]

• Building an all-fiber watt-level femtosecond laser pumping source using chirped pulse amplification and fiber compression. • Bridging high numerical aperture fibers for low-loss fusion splicing. • Utilizing Ge-doped fiber as a nonlinear medium to realize a watt-level high-flatness supercontinuum source. • The output supercontinuum pulse is a noise-like pulse with a tip pulse duration of only 62 fs. • The whole supercontinuum laser system is characterized by compactness and high stability. The high-power ultra-flat supercontinuum (SC) sources play an important role in various fields. In this letter, we experimentally demonstrated an all-fiber, high-power, ultra-flat SC source in GeO 2 highly nonlinear fiber (HNLF) pumped by a femtosecond fiber laser system. The system is mode-locked by a semiconductor saturable absorber mirror with an all-polarization-maintaining (PM) structure. Based on the technology of chirped pulse amplification, a maximum power of 3.12 W was realized with a repetition rate of 80 MHz at 1.56 μm, and the pulse duration was compressed to 124 fs in a segment of PM single-mode fiber. Furthermore, by optimizing the length of the HNLF, a wideband SC spectrum of nearly 700 nm was obtained at10 dB with a maximum power of 1.82 W, and the flatness of the spectrum was better than 5 dB in the range of 1600–2200 nm. We observed that the pulse evolved into a noise-like pulse with a narrowest pulse duration of 62 fs. Thanks to the all-PM structure of the fiber laser, the long-term stability of SC power was manifested with a relative fluctuation as low as 0.53 % over 6 h. [ABSTRACT FROM AUTHOR]

Abstract: We demonstrate an ytterbium-doped fiber (YDF) laser being able to generate dark pulses and Q-switched pulses by using a graphene oxide (GO) based composite as saturable absorber (SA). These operation regimes are realized for the first time in a 1-μm band fiber laser as far as our best knowledge. In the fabrication of GO based saturable absorber (GOSA), a vertical evaporation process is included, which results in a GO concentration and thickness variable SA. The generated dark pulse has pulse duration in ns-scale. In the Q-switched operation, pulses with durations from 5.321μs to 2.655μs and repetition rates from 28.47kHz to 58.95kHz can be obtained as the launched pump power is changed. The transition from the dark pulse to Q-switched operations can be clearly seen as the pump power is increased to a certain value. The radio frequency (RF) and optical spectrum variations with respect to the change of pump power have also been analyzed in detail. [Copyright &y& Elsevier]

• Mode-locked fluoride fiber laser (MLFFL) operating in noise-like pulse (NLP) regime. • All-PM Mode-locked fluoride fiber laser. • Insights into the complex nonlinear behavior of NLPs in MLFFL. A 976-nm pulse-type switchable mode-locked fiber laser is experimentally demonstrated, for the first time to our knowledge, with a single mode fiber-graded index multimode fiber-single mode fiber (SMF-GIMF-SMF) structure-based saturable absorber (SA). The GIMF is bent into a given state to strengthen its effect on establishing mode-locking. By adjusting the intra-cavity polarization controller, the switching between dissipative solitons (DSs) and noise-like pulses (NLPs) can be achieved. Meanwhile, we also realize a second harmonic mode-locking (HML) in the same laser cavity. The laser provides a solution to realize 976 nm mode-locking operation with a simple and low-cost configuration and can serve as a potential tool for various applications. [ABSTRACT FROM AUTHOR]

A stable dissipative soliton (DS) erbium-doped fiber (EDF) laser passively mode locked by InSb saturable absorber (SA) is achieved for the first time. The used InSb SA is prepared by magnetron-sputtering deposition (MSD) method based on tapered fiber. The achieved stable dissipative soliton (DSs) possess a central wavelength of 1570 nm, pulse duration of 25.14 ps, repetition rate of 14.91 MHz, and a maximum average output power of 11.57 mW, respectively. The experiment verifies the merits of high thermal damage resistance, superb long-term stability and excellent antioxidant capacity of the prepared InSb SA, as well enriches in-depth DSs researches based on 2D-material SAs. [ABSTRACT FROM AUTHOR]

• A 12° TFBG is prepared by femtosecond laser direct inscription method. And a pulse multi-wavelength erbium-doped fiber laser (EDFL) passively Q-switched by the as-prepared 12° TFBG is exclusively and systematically demonstrated for the first time. The discussed result is interesting and may add new knowledge within the field of research. • The transmission spectrum of 12° TFBG and the polarization dependent loss (PDL) declare that the 12° TFBG can serve as both a filter and a polarizer. So, in the paper, it's not only systematically verified that the 12° TFBG is capable of acting an ideal modulator for ultrafast pulse generation, but also the multi-wavelength Q-switched operation obtained in this work benefits from the filtering effect and polarization dependent loss (PDL) effect of the 12° TFBG. • The experimental results are comparable to other Q-switched multi-wavelength EDFLs reported so far, and during the experiment, the 12° TFBG exhibits excellent stability and reliability. • The work not only provides a reliable reference about the equivalent SA performance of 12° TFBG, but also enriches the studies of passively Q-switched lasers based on different kinds of modulators. Sufficient attention from researchers should be focused on relative studies, which may open up a new research field in the nearest future. As a promising small-angle TFBG, the 12° tilted fiber Bragg grating (TFBG) has been successfully used in biochemical sensors, fiber optic anemometers, and continuously tunable photon fraction time differentiators. On the other hand, multi-wavelength Q-switched fiber lasers have widely potential and practical applications in various fields, such as laser processing, laser marking, medical diagnosis, military applications, and so on. In this paper, first, a 12° TFBG is prepared by femtosecond laser direct inscription method (FSL-DIM), then, a pulse multi-wavelength erbium-doped fiber laser (EDFL) passively Q-switched by the as-prepared 12° TFBG is exclusively and systematically demonstrated for the first time. When the pump power is raised from 100 mW to 500 mW, the repetition rate is boosted from 51.64 kHz to 149.4 kHz resulting in a repetition rate range about 97.76 kHz, while the pulse duration is compressed from 3.928 μs to 1.033 μs. The average output power monotonically increases up to the maximum value of 6.357 mW corresponding to the maximum pulse energy of 42.55 nJ. The signal-to-noise ratio (SNR) is measured to be 53 dB, which indicates a high stability. The experimental results are comparable to other Q-switched multi-wavelength EDFLs reported so far, and during the experiment, the 12° TFBG exhibits excellent stability and reliability. As far as we can explain, the multi-wavelength Q-switched operation obtained in this paper benefits from the filtering effect and polarization dependent loss (PDL) effect of the 12° TFBG. The work not only provides a reliable reference about the effective-SA performance of 12° TFBG, but also enriches the studies of passively Q-switched lasers based on different kinds of modulators. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a comb multi-wavelength, nanosecond rectangular pulse, passively mode-locked Erbium-doped fiber (EDF) laser. A section of un-pumped EDF had been employed to optimize the multi-wavelength pulses for the first time to the best of our knowledge. The un-pumped EDF absorbs the unwanted the short-wavelength lasing and optimizes the gain, therefore allowing for the enhancement of the long-wavelength lasing. Because of the gain competition effect in the un-pumped EDF, the output wavelength line number of the fiber laser can be significantly increased from three wavelengths to twenty lasing wavelengths. The mode-locked pulse has a rectangular temporal profile with pump power dependent pulse duration. Experimental results illustrate that the fiber laser has a good stability at room temperature. This work provides a new configuration for the design of multi-wavelength, rectangular nanosecond pulse that may fit for specific applications. [ABSTRACT FROM AUTHOR]

We have grown ultrathin quartz plate-based multilayer molybdenum disulfide (MoS 2 ) by chemical vapor deposition (CVD). When employed as saturable absorber (SA), the prepared MoS 2 device exhibits remarkable merits (e.g. uniform thickness, high quality of crystal lattice high damage threshold easy fabrication and good practicability). The modulation depth, saturable intensity, and non-saturable loss of this SA device are measured to be 16.1%, 0.438 MW/cm 2 and 44.6% respectively. By incorporating the SA into a typical ring cavity erbium-doped fiber laser, stable passive soliton mode-locked pulse is achieved with the repetition frequency of 0.987 MHz, the signal noise ratio (SNR) of 71.4 dB and the pulse duration of 2.17 ps. The experimental results demonstrate our MoS 2 -SA device to be an effective mode locker, and it is promising to be used in ultrafast photonics. [ABSTRACT FROM AUTHOR]

Tm-doped ultrafast fiber lasers have been widely used in scientific research and industrial applications. Here, with the usage of an novel integrated fiber coupler, we describe a reduced laser configuration to achieve compact and high-performance all-fiber Tm-doped mode-locked fiber laser. This novel fiber component can be used as wavelength division multiplexer (WDM), output coupler (OC) and optical modulator at the same time, fabricated by magnetron-sputtering vanadium dioxide (VO 2) saturable absorber (SA) on a optical coupler. The bare coupler was laboratory-tapered performing WDM and OC simultaneously. With above-mentioned device, a mode-locked Tm-doped fiber laser was constructed. Fundamental solitons were formed and generated with a short pulse width of 478 fs and a high repetition rate of 160 MHz. In addition, Short-term and long-term laser stability was confirmed by the noise analysis and 4-h running test. 336 fs RMS time jitter ([10 kHz - 10 MHz]) and 0.036% RMS relative intensity noise ([1 Hz - 10 MHz]) was acquired. This new integrated design at 2 μm region simplifies implementation of the ultrafast Tm-doped fiber laser and paves the way for developing compact and high-performance all-fiber ring laser. • Integrated fiber component simplifying the implementation of 2 μm ultrafast fiber laser was firstly demonstrated. • A new kind of oxide saturable absorber VO 2 was demonstrated to be suitable for such multi-function device in 2 μm. • High quality solitons (478 fs/160 MHz) directly generated from all-fiber SA-based oscillator without any compression. [ABSTRACT FROM AUTHOR]

• A WDM/OC/SA/TDF multifunctional integrated tapered coupler is proposed for the first time. • The thulium-doped mode-locked fiber laser with fundamental repetition frequency (214 MHz) was realized. • The highest repetition rate (2.14 GHz) of harmonic mode-locking in 2 μm region was obtained, which corresponded to the 10th HML of fundamental repetition frequency. We report a WDM/OC/SA/TDF multifunctional integrated tapered coupler for the first time. By magnetron sputtering WTe 2 on the conical region of the coupler, it can be served as a wavelength division multiplexer (WDM), output coupler (OC), saturable absorber (SA), and gain medium. The thulium-doped mode-locked fiber laser based on such integrated device was centered at 1966.6 nm with 450 fs duration and a fundamental repetition frequency of 214 MHz. The long-term operating stability and the noise feature of mode-locked laser was also characterized. At the same time, the 10th harmonic mode-lockeing (HML) at the repetition rate of 2.14 GHz was demonstrated in the cavity, to the best of our knowledge, which was the highest repetition rate reported for SA-based mode-locked fiber lasers in 2 µm region. [ABSTRACT FROM AUTHOR]

• This study is the first for demonstrating ultrafast synchronously pumped mode-locked fiber laser in the all-normal-dispersion regime. • The synchronously pumped mode-locked fiber laser is developed with an all-polarization-maintaining architecture, and it avoids the usage of saturable absorbers or intracavity modulators. Therefore, it exhibits excellent environmental stability and self-starting capacity. • Experimental works were conducted for investigating the mode-locking mechanism, and the results indicate that the dominant modulation effect is the cross-phase modulation induced by the pulsed pump source. Synchronously pumped mode-locking, which avoids the usage of saturable absorbers or intracavity modulators, is a promising technique to generate ultrashort pulses for industrial applications. However, because of the lack of all-fiber single-mode ultrafast pump sources, it is difficult to apply this technique in ytterbium-doped fiber lasers (YDFLs). To the best of our knowledge, this study has demonstrated a synchronously pumped mode-locked ultrafast YDFL for the first time. Based on a home-built 976-nm pulsed fiber laser as the pump, it generates dissipative solitons with a pulse duration of 31.3 ps and a repetition frequency of ∼ 27.95 MHz. The laser is developed with an all-polarization-maintaining architecture; therefore, it exhibits excellent environmental stability and self-starting capacity. Furthermore, we have also conducted experimental work for investigating the mechanism of this mode-locking technique. The results indicate that instead of the gain modulation effect, the pulsed pump-induced cross-phase modulation effect plays a dominant role in pulse shaping. This study demonstrates a potential strategy for realizing high-performance ultrafast fiber sources in the spectral regions without efficient modulators or saturable absorbers. [ABSTRACT FROM AUTHOR]

Material with nonlinear response to light intensity, i.e., the saturable absorber, is an important mean to realize pulsed lasers which have wide applications in many fields. In this paper, we report a broadband optical-intensity modulator, magnetron-sputtered GaSb thin film, for pulse generation from C-band to mid-infrared regions. By the virtue of GaSb thin film, soliton pulses with 308 fs/585 fs pulse width and 17.82 mW/64.69 mW output power were obtained at 1559 nm/1902 nm in an Er-doped fiber laser (EDFL) and a Tm-doped fiber laser (TDFL) respectively. Furthermore, GaSb thin film coated on a gold mirror was successfully used to achieve 2783 nm Q-switching operation of a Er3+:ZBLAN fiber laser with a maximum output power of 420 mW. With such a wide operation wavelength range, GaSb thin film is of great potential for many nonlinear optical applications. • For the first time, it is demonstrated GaSb thin film can be used as a broadband saturable absorber. • The saturable absorption of GaSb thin film at 1.5 μm and 2.8 μm regions were explored. • Pulsed fiber lasers based on GaSb film were constructed operating at wavelength ranging from 1.5 μm to 2.8 μm. • High quality 2.8 μm Q-switched pulses were generated by GaSb-coated gold mirror. [ABSTRACT FROM AUTHOR]