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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]

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]

Ultrafast fiber lasers with a wide spectral range have huge demands for many applications. In this article, magnetron sputtering deposition (MSD) technique was utilized to prepare a new broadband microfiber based Sb thin film saturable absorber (SA), and ultrafast pulses in both 1.5 and 2 μm wavebands were generated with the integrated microfiber-based Sb thin film SA in erbium-doped fiber laser (EDFL) and thulium-doped fiber laser (TDFL), respectively. Pulse duration of 544 fs/972 fs and output power of 21.76 mW/36.1 mW centered at 1557 nm/1892 nm were respectively produced from stable mode-locked EDFL and TDFL. To the best our knowledge, this is the first time that ultrafast fiber lasers including both 1.5 μm and 2 μm wavebands were mode locked by a single microfiber-based Sb thin film SA. [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]

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 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]

• Fabrication of perovskite materials explained briefly. • Crystal structure and nonlinear optical properties of perovskite materials. • A brief description of some current applications of perovskite from near-infrared to mid-infrared lasers. • Research progress of Q-switched lasers, and mode-locked lasers by employing perovskite materials. • Future prospects of perovskite materials are discussed and analyzed. 2D perovskite materials have merged as a novel addition to the family of saturable absorbers, offering the capability to generate high-energy and ultrashort pulses due to their distinct optoelectronic properties, as well as their structure and chemical versatility. In recent times, numerous reports have highlighted the progress of ultrafast pulsed lasers utilizing perovskite materials, which indicates a positive and promising outlook for advancements in this area. This review provides a summary of the crystal structure and nonlinear optical properties of perovskite materials. Fabrication methods of perovskites are divided into hybrid organic–inorganic, all-inorganic perovskite materials, and Ruddlesden-Popper perovskite materials based on their components. Subsequently, we provided a systematic introduction to ultrafast lasers that utilized perovskite materials across different spectral bands. Finally, an analysis of present challenges and perspectives for the advancement of ultrafast lasers facilitated by perovskite materials is presented. [ABSTRACT FROM AUTHOR]

• 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]

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]

• The high output power at 1.8 μm could be achieved from a Tm:YAP laser. • The polarizations of the laser beams at 1.82 μm and 1.84 μm are orthogonal. • The 1.82 μm is the shortest wavelength achieved from a CWML Tm-doped bulk laser. We have experimentally demonstrated both 1.82 μm and 1.84 μm Tm:YAP lasers at the operation mode of continuous-wave (CW) and mode-locking. These individual wavelength lasers are realized by using well-chosen output couplers. For the CW operation, a short Fabry-Perot cavity is employed. The maximum output power of the 1825 nm Tm:YAP laser is 7.04 W, and the corresponding slope efficiency is 59.3%. For 1844 nm Tm:YAP laser, the output power is 7.1 W. A commercial semiconductor saturable absorber mirror (SESAM) is used for realizing continuous-wave mode-locking (CWML) operation. The average output power of Tm:YAP laser at 1823.7 nm is 0.3 W, and the pulse duration is 126 ps. Further, stable CWML laser operating at 1844 nm is realized by inserting a 5 mm fused-quartz plate into the cavity with the Brewster angle. The average output power of 0.63 W is achieved, and the pulse duration is 156 ps. [ABSTRACT FROM AUTHOR]