Showing papers on "Fiber laser published in 2018"

Sub-200 fs soliton mode-locked fiber laser based on bismuthene saturable absorber

Abstract: Few-layer bismuthene is an emerging two-dimensional material in the fields of physics, chemistry, and material science. However, its nonlinear optical property and the related photonics device have been seldom studied so far. Here, we demonstrate a sub-200 fs soliton mode-locked erbium-doped fiber laser (EDFL) using a microfiber-based bismuthene saturable absorber for the first time, to the best of our knowledge. The bismuthene nanosheets are synthesized by the sonochemical exfoliation method and transferred onto the taper region of a microfiber by the optical deposition method. Stable soliton pulses centered at 1561 nm with the shortest pulse duration of about 193 fs were obtained. Our findings unambiguously imply that apart from its fantastic electric and thermal properties, few-layer bismuthene may also possess attractive optoelectronic properties for nonlinear photonics, such as mode-lockers, Q-switchers, optical modulators and so on.

Passively mode-locked Er-doped fiber laser based on SnS 2 nanosheets as a saturable absorber

Abstract: In this paper, tin disulfide (SnS2), a two-dimensional (2D) n-type direct bandgap layered metal dichalcogenide with a gap value of 2.24 eV, was employed as a saturable absorber. Its appearance and nonlinear saturable absorption characteristics were also investigated experimentally. SnS2-PVA (polyvinyl alcohol) film was successfully prepared and employed as a mode-locker for achieving a mode-locked Er-doped fiber laser with a pulse width of 623 fs at a pulse repetition rate of 29.33 MHz. The results prove that SnS2 nanosheets will have wide potential ultrafast photonic applications due to their suitable bandgap value and excellent nonlinear saturable absorption characteristics.

Few-layer bismuthene for ultrashort pulse generation in a dissipative system based on an evanescent field.

Abstract: Bismuthene has attracted a great deal of attention because of its unique electronic and optical properties. However, there are few reported applications of bismuthene in nonlinear optical applications. In this research, a dissipative soliton ytterbium-doped mode-locked fiber laser at 1 μm regime with a bismuthene saturable absorber (SA) by using evanescent field interaction for the first time is demonstrated. The nonlinear optical absorption of microfiber-based bismuthene SA is shown experimentally by using a homemade ultrafast fiber laser, whose saturation intensity and modulation depth are about 13 MW cm-2 and 2.2%, respectively. Relying on the excellent nonlinear optical property of the bismuthene SA, the typical dissipative solitons with a repetition rate of 21.74 MHz are generated at a center wavelength of 1034.4 nm. The time-bandwidth product of the pulse is about 23.07 with a pulse width of 30.25 ps. The results demonstrate that bismuthene is a good candidate for application in a 1 μm wave-breaking-free mode-locked fiber laser and nonlinear photonic components.

Frontiers of Mid-IR Lasers Based on Transition Metal Doped Chalcogenides

Abstract: Enabling broad tunability, high peak and average power, ultrashort pulse duration, and all known modes of laser operation—transition-metal (TM)-doped II–VI chalcogenides are the materials of choice for direct lasing in the mid-IR. The host materials feature broad infrared transparency, high thermal conductivity, low phonon cutoff, low optical losses, and are available as either single crystals or polycrystalline ceramics. Doped with TM ions, these media exhibit a four-level energy structure, the absence of excited state absorption, as well as broad absorption and emission bands. Doped single-crystals of high optical quality are difficult to grow; however, the advent of postgrowth diffusion doped ceramics has resulted in significant progress in laser development. Here, we summarize recent experimental laser results on Cr and Fe doped II–VI chalcogenides providing access to the 1.8–6 μm spectral range with a high (>60%) efficiency, multi-Watt-level [140 W in continuous wave (CW)] output powers, tunability of >1000 nm, short-pulse (<16 fs) multi-Watt oscillation, and multi-Joule output energies in free running and gain-switched regimes. We also review recent results on hybrid fiber-bulk (Er-fiber/Er:YAG, Tm-fiber: Ho:YAG/YLF) systems combining high efficiency of CW fiber lasers with high pulse energies of bulk materials and serving as pump sources of gain-switched Cr:II-VI lasers.

Towards power scaling of 2.8 μm fiber lasers

Abstract: We report the demonstration of a 2824 nm passively cooled erbium-doped fluoride fiber laser delivering a record average output power of 416 W in continuous-wave operation The splice-less cavity is based on intra-core fiber Bragg gratings written directly in the active erbium-doped fluoride fiber, which is bidirectionally pumped at 980 nm to reduce heat load To the best of our knowledge, this result is the highest average output power achieved with a mid-infrared fiber laser The long-term performance of different protective endcaps is also investigated at high-power operation

Multimode Nonlinear Fiber Optics: Massively Parallel Numerical Solver, Tutorial, and Outlook

Abstract: Building on the scientific understanding and technological infrastructure of single-mode fibers, multimode fibers are being explored as a means of adding new degrees of freedom to optical technologies such as telecommunications, fiber lasers, imaging, and measurement. Here, starting from a baseline of single-mode nonlinear fiber optics, we introduce the growing topic of multimode nonlinear fiber optics. We demonstrate a new numerical solution method for the system of equations that describes nonlinear multimode propagation, the generalized multimode nonlinear Schrodinger equation. This numerical solver is freely available, implemented in MATLAB and includes a number of multimode fiber analysis tools. It features a significant parallel computing speed-up on modern graphical processing units, translating to orders-of-magnitude speed-up over the conventionally-used split-step Fourier method. We demonstrate its use with several examples in graded- and step-index multimode fibers. Finally, we discuss several key open directions and questions, whose answers could have significant scientific and technological impact.

Passively Q-Switched and Mode-Locked Fiber Laser Based on an ReS2 Saturable Absorber

Abstract: Transition metal dichalcogenides, a family of two-dimensional material with unusual electronic, optical, mechanical, and electrochemical properties, have received much research attention in recent years. Here we demonstrate that, another type of few-layer transition metal dichalcogenides, rhenium disulfide (ReS2) nanosheets display saturable absorption property at 1.55 μm. By incorporating the ReS2 nanosheets with the polyvinyl alcohol (PVA), a film-type ReS2-PVA saturable absorber is fabricated to realize Q-switching and mode locking of erbium-doped fiber lasers. The repetition rate of the Q-switched laser pulses varies from 12.6 to 19 KHz while the duration changes from 23 to 5.496 μs by tuning the pump from 45 to 120 mW. By optimizing the polarization state, the mode-locked operation is also obtained, emitting a train of pulses centered at 1558.6 nm with the duration of 1.6 ps and the fundamental repetition rate of 5.48 MHz. It is demonstrated that ReS2 nanosheets have the similar saturable absorption property as that of MoS2 and WS2, and may find potential applications in pulsed laser, optical modulators, and sensors.

Ultrathin 2D Transition Metal Carbides for Ultrafast Pulsed Fiber Lasers

Abstract: Two-dimensional (2D) materials, such as graphene, transition metal dichalcogenides, and black phosphorus, have attracted intense interest for applications in ultrafast pulsed laser generation, owing to their strong light–matter interactions and large optical nonlinearities. However, due to the mismatch of the bandgap, many of these 2D materials are not suitable for applications at near-infrared (NIR) waveband. Here, we report nonlinear optical properties of 2D α-Mo2C crystals and the usage of 2D α-Mo2C as a new broadband saturable absorber for pulsed laser generation. It was found that 2D α-Mo2C crystals have excellent saturable absorption properties in terms of largely tunable modulation depth and very low saturation intensity. In addition, ultrafast carrier dynamic results of 2D α-Mo2C reveal an ultrashort intraband carrier recovery time of 0.48 ps at 1.55 μm. By incorporating 2D α-Mo2C saturable absorber into either an Er-doped or Yb-doped fiber laser, we are able to generate ultrashort pulses with ver...

Materials for optical fiber lasers: A review

Abstract: Over the past two decades, fiber laser technologies have matured to such an extent that they have captured a large portion of the commercial laser marketplace. Yet, there still is a seemingly unquenchable thirst for ever greater optical power to levels where certain deleterious light-matter interactions that limit continued power scaling become significant. In the past decade or so, the industry has focused mainly on waveguide engineering to overcome many of these hurdles. However, there is an emerging body of work emphasizing the enabling role of the material. In an effort to underpin these developments, this paper reviews the relevance of the material in high power fiber laser technologies. As the durable material-of-choice for the application, the discussion will mainly be limited to silicate host glasses. The discussion presented herein follows an outward path, starting with the trivalent rare earth ions and their spectroscopic properties. The ion then is placed into a host, whose impact on the spectroscopy is reviewed. Finally, adverse interactions between the laser lightwave and the host are discussed, and novel composition glass fiber design and fabrication methodologies are presented. With deference to the symbiosis required between material and waveguide engineering in active fiber development, this review will emphasize the former. Specifically, where appropriate, materials-based paths to the enhancement of laser performance will be underscored.

Black phosphorus Q-switched and mode-locked mid-infrared Er:ZBLAN fiber laser at 3.5 μm wavelength

Abstract: With the proposal of dual-wavelength pumping (DWP) scheme, DWP Er:ZBLAN fiber lasers at 3.5 μm have become a fascinating area of research. However, limited by the absence of suitable saturable absorber, passively Q-switched and mode-locked fiber lasers have not been realized in this spectral region. Based on the layer-dependent bandgap and excellent photoelectric characteristics of black phosphorus (BP), BP is a promising candidate for saturable absorber near 3.5 μm. Here, we fabricated a 3.5-μm saturable absorber mirror (SAM) by transferring BP flakes onto a Au-coated mirror. With the as-prepared BP SAM, we realized Q-switching and mode-locking operations in the DWP Er:ZBLAN fiber lasers at 3.5 μm. To the best of our knowledge, it is the first time to achieve passively Q-switched and mode-locked pulses in 3.5 μm spectral region. The research results will not only promote the development of 3.5-μm pulsed fiber lasers but also open the photonics application of two-dimensional materials in this spectral region.

Mode-locked Er-doped fiber laser based on PbS/CdS core/shell quantum dots as saturable absorber

Abstract: Previously, PbS/CdS core/shell quantum dots with excellent optical properties have been widely used as light-harvesting materials in solar cell and biomarkers in bio-medicine. However, the nonlinear absorption characteristics of PbS/CdS core/shell quantum dots have been rarely investigated. In this work, PbS/CdS core/shell quantum dots were successfully employed as nonlinear saturable absorber (SA) for demonstrating a mode-locked Er-doped fiber laser. Based on a film-type SA, which was prepared by incorporating the quantum dots with the polyvinyl alcohol (PVA), mode-locked Er-doped operation with a pulse width of 54 ps and a maximum average output power of 2.71 mW at the repetition rate of 3.302 MHz was obtained. Our long-time stable results indicate that the CdS shell can effectively protect the PbS core from the effect of photo-oxidation and PbS/CdS core/shell quantum dots were efficient SA candidates for demonstrating pulse fiber lasers due to its tunable absorption peak and excellent saturable absorption properties.

Several new directions for ultrafast fiber lasers [Invited].

Abstract: Ultrafast fiber lasers have the potential to make applications of ultrashort pulses widespread – techniques not only for scientists, but also for doctors, manufacturing engineers, and more. Today, this potential is only realized in refractive surgery and some femtosecond micromachining. The existing market for ultrafast lasers remains dominated by solid-state lasers, primarily Ti:sapphire, due to their superior performance. Recent advances show routes to ultrafast fiber sources that provide performance and capabilities equal to, and in some cases beyond, those of Ti:sapphire, in compact, versatile, low-cost devices. In this paper, we discuss the prospects for future ultrafast fiber lasers built on new kinds of pulse generation that capitalize on nonlinear dynamics. We focus primarily on three promising directions: mode-locked oscillators that use nonlinearity to enhance performance; systems that use nonlinear pulse propagation to achieve ultrashort pulses without a mode-locked oscillator; and multimode fiber lasers that exploit nonlinearities in space and time to obtain unparalleled control over an electric field.

Room-temperature fiber laser at 3.92 μm

Abstract: Rare-earth-doped fiber lasers are promising contenders in the development of spectroscopy, free-space communications, and countermeasure applications in the 3–5 μm spectral region. However, given the limited transparency of the commonly used fluorozirconate glass fiber, these systems have only achieved wavelength coverage up to 3.8 μm, hence fueling the development of more suitable fiber glass compositions. To this extent, we propose in this Letter a novel heavily holmium-doped fluoroindate fiber, providing extended transparency up to 5 μm, to demonstrate the longest wavelength room-temperature fiber laser at 3.92 μm. Achieving ∼200 mW of output power when cladding pumped by a commercial 888 nm laser diode, this demonstration paves the way for powerful mid-infrared fiber lasers emitting at and beyond 4 μm.

High energy soliton pulse generation by a magnetron-sputtering-deposition-grown MoTe 2 saturable absorber

Abstract: The pulse energy in the ultrafast soliton fiber laser oscillators is usually limited by the well-known wave-breaking phenomenon owing to the absence of a desirable real saturable absorber (SA) with high power tolerance and large modulation depth. Here, we report a type of microfiber-based MoTe2 SA fabricated by the magnetron-sputtering deposition (MSD) method. High-energy wave-breaking free soliton pulses were generated with pulse duration/pulse energy/average output power of 229 fs/2.14 nJ/57 mW in the 1.5 μm regime and 1.3 ps/13.8 nJ/212 mW in the 2 μm regime, respectively. To our knowledge, the generated soliton pulses at 1.5 μm had the shortest pulse duration and the highest output power among the reported erbium-doped fiber lasers mode locked by transition metal dichalcogenides. Moreover, this was the first demonstration of a MoTe2-based SA in fiber lasers in the 2 μm regime, and the pulse energy/output power are the highest in the reported thulium-doped fiber lasers mode locked by two-dimensional materials. Our results suggest that a microfiber-based MoTe2 SA could be used as an excellent photonic device for ultrafast pulse generation, and the MSD technique opens a promising route to produce a high-performance SA with high power tolerance and large modulation depth, which are beneficial for high-energy wave-breaking free pulse generation.

Exploration in Performance Scaling and New Application Avenues of Superfluorescent Fiber Source

Abstract: Thanks to the unique properties such as spatially coherent, broadband emission spectrum, and high temporal stability, superfluorescent fiber source (SFS) has shown tremendous potential in wide applications of sensing, imaging, spectroscopy, and material processing. The fast development of active fiber and pump diode provides unprecedented opportunity for the performance scaling of SFS. In this paper, the new horizon opened by the recently developed SFS will be reviewed. First, the output power scaling of SFS with different architectures will be summarized, and a kilowatt-level high power SFS based on a tandem pumping technique will be demonstrated for the first time. Second, spectrum manipulation of SFS, including coverage extending and spectrum shaping, will be introduced in detail. What is more, the spectrum evolution of narrowband SFS in power scaling will be numerically modeled and evaluated. Third, several novel applications of SFS, including midinfrared laser generation, nonlinear effect suppression, sensing, and imaging, will be given, indicating the versatile performance of SFS compared with traditional fiber laser oscillators. Based on the new developed SFS, we will present the first hundred-watt level linearly polarized random fiber laser. In the last section, future endeavors on SFS will be presented.

Dual-comb spectroscopy with a single free-running thulium-doped fiber laser.

Abstract: We demonstrate dual-comb spectroscopy in the vicinity of 2 µm wavelength based on a single dual-wavelength dual-comb Thulium-doped fiber laser. The shared laser cavity ensures passively maintained mutual coherence between the two combs due to common mode environmental noise rejection. In a proof-of-principle experiment, the absorption characteristics caused by the water in the optical path that composes the dual-comb spectrometer are measured. The retrieved spectral positions of the water absorption dips match with the HITRAN database.

2D bismuthene fabricated via acid-intercalated exfoliation showing strong nonlinear near-infrared responses for mode-locking lasers

Abstract: The rediscovery of black phosphorus (BP) has expanded the 2D family into Group 15 (Nitrogen Group) elements, among which bismuthene is the latest member with extraordinary opto-electronic, catalytic and biocompatible properties and potential as a 2D topological insulator. However, bulk Bi is not easily mechanically exfoliated as its counterpart of BP. Thus, to date, the reports on 2D Bi fabrication are rare, and investigations on its nonlinear optical properties are even less. Herein, we rationally designed a new strategy combining acid-interaction and liquid exfoliation to successfully transform metal bulk Bi into few-layer semiconductor, which resulted in unseen opto-electronic properties, such as tunable nonlinear responses all the way to the near-infrared (NIR) region. This band is critical for telecommunication and military purposes, but currently, functioning materials are extremely scarce. The origin of this strong saturable absorption was thoroughly explored through time-resolved spectroscopy spanning from the fs to μs timescale, which indicated ultrafast fs to ps carrier dynamics in the early stage and long exciton bleaching recovery up to μs. As a proof-of-concept application, the as-prepared 2D Bi was employed as a saturable absorber to mode-lock a Tm-doped fiber laser and successfully realized a 2 μm NIR-wavelength output. This study not only offers an effective and scalable method to fabricate the new 2D family member bismuthene with extraordinary stability, but also explores its strong and broad nonlinear responses extending into the NIR region and fundamental photoinduced dynamics, which demonstrate the full potential of 2D Bi for application in opto-electronic devices and nonlinear optics.

Deep learning and model predictive control for self-tuning mode-locked lasers

Abstract: Self-tuning optical systems are of growing importance in technological applications such as mode-locked fiber lasers. Such self-tuning paradigms require intelligent algorithms capable of inferring approximate models of the underlying physics and discovering appropriate control laws in order to maintain robust performance for a given objective. In this work, we demonstrate the first integration of a deep-learning (DL) architecture with model predictive control (MPC) in order to self-tune a mode-locked fiber laser. Not only can our DL-MPC algorithmic architecture approximate the unknown fiber birefringence, it also builds a dynamical model of the laser and appropriate control law for maintaining robust, high-energy pulses despite a stochastically drifting birefringence. We demonstrate the effectiveness of this method on a fiber laser that is mode-locked by nonlinear polarization rotation. The method advocated can be broadly applied to a variety of optical systems that require robust controllers.

102 fs pulse generation from a long-term stable, inkjet-printed black phosphorus-mode-locked fiber laser.

Abstract: We demonstrate a long-term stable, all-fiber, erbium-doped femtosecond laser mode-locked by a black phosphorus saturable absorber. The saturable absorber, fabricated by scalable and highly controllable inkjet printing technology, exhibits strong nonlinear optical response and is stable for long-term operation against intense irradiation, overcoming a key drawback of this material. The oscillator delivers self-starting, 102 fs stable pulses centered at 1555 nm with 40 nm spectral bandwidth. This represents the shortest pulse duration achieved from black phosphorus in a fiber laser to date. Our results demonstrate the great potential for black phosphorus as an excellent candidate for long-term stable ultrashort pulse generation.

Recent advances in infrared laser lithotripsy [Invited].

Abstract: The flashlamp-pumped, solid-state, pulsed, mid-infrared, holmium:YAG laser (λ = 2120 nm) has been the clinical gold standard laser for lithotripsy for over the past two decades. However, while the holmium laser is the dominant laser technology in ureteroscopy because it efficiently ablates all urinary stone types, this mature laser technology has several fundamental limitations. Alternative, mid-IR laser technologies, including a thulium fiber laser (λ = 1908 and 1940 nm), a thulium:YAG laser (λ = 2010 nm), and an erbium:YAG laser (λ = 2940 nm) have also been explored for lithotripsy. The capabilities and limitations of these mid-IR lasers are reviewed in the context of the quest for an ideal laser lithotripsy system capable of providing both rapid and safe ablation of urinary stones.

Watt-scale super-octave mid-infrared intrapulse difference frequency generation

Abstract: The development of high-power, broadband sources of coherent mid-infrared radiation is currently the subject of intense research that is driven by a substantial number of existing and continuously emerging applications in medical diagnostics, spectroscopy, microscopy, and fundamental science. One of the major, long-standing challenges in improving the performance of these applications has been the construction of compact, broadband mid-infrared radiation sources, which unify the properties of high brightness and spatial and temporal coherence. Due to the lack of such radiation sources, several emerging applications can be addressed only with infrared (IR)-beamlines in large-scale synchrotron facilities, which are limited regarding user access and only partially fulfill these properties. Here, we present a table-top, broadband, coherent mid-infrared light source that provides brightness at an unprecedented level that supersedes that of synchrotrons in the wavelength range between 3.7 and 18 µm by several orders of magnitude. This result is enabled by a high-power, few-cycle Tm-doped fiber laser system, which is employed as a pump at 1.9 µm wavelength for intrapulse difference frequency generation (IPDFG). IPDFG intrinsically ensures the formation of carrier-envelope-phase stable pulses, which provide ideal prerequisites for state-of-the-art spectroscopy and microscopy. A table-top-sized, coherent light source that offers a compact and bright alternative to a synchrotron in the 4−18 µm spectral range has been developed by a German-US research team. The team used a novel ultrashort (16 fs) pulse, high power Tm-doped fiber laser operating at 1.9 µm to induce a nonlinear frequency downconversion process called intrapulse difference frequency generation in a crystal of GaSe. The broad spectral coverage and high brightness render this mid-infrared source a unique tool for state-of-the art spectroscopy and microscopy. The team says that the compactness and simplicity of the presented approach brings exciting prospects for the future accessibility, in particular for emerging applications that are currently addressed only with mid-infrared beamlines in large-scale synchrotron facilities.

Buildup dynamics of dissipative soliton in an ultrafast fiber laser with net-normal dispersion

Abstract: Taking advantage of technology of spatio-temporal reconstruction and dispersive Fourier transform (DFT), we experimentally observed the buildup dynamics of dissipative soliton in an ultrafast fiber laser in the net-normal dispersion regime. The soliton buildup dynamics were analyzed in both the spectral and temporal domains. We firstly revealed that the appearing of the spectral sharp peaks with oscillation structures during the mode-locking transition is caused by the formation of structural dissipative soliton. The experimental results were explained by the numerical simulations. These findings would give some new insights into the dissipative soliton buildup dynamics in ultrafast fiber lasers.

Black phosphorus Q-switched and mode-locked Er:ZBLAN fiber lasers at 3.5 um

Abstract: With the proposal of dual-wavelength pumping (DWP) scheme, DWP Er:ZBLAN fiber lasers at 35 um have become a fascinating area of research However, limited by the absence of suitable saturable absorber, passively Q-switched and mode-locked fiber lasers have not been realized in this spectral region Based on the layer-dependent bandgap and excellent photoelectric characteristics of black phosphorus (BP), BP is a promising candidate for saturable absorber near 35 um Here, we fabricated a 35-um saturable absorber mirror (SAM) by transferring liquid-phase exfoliated BP flakes onto a gold-coated mirror With the as-prepared BP SAM, we realized stable Q-switching and continuous-wave mode-locking operations in the DWP Er:ZBLAN fiber lasers at 35 um To the best of our knowledge, it is the first time to achieve passively Q-switched and mode-locked pulses in 35 um spectral region The research results will not only promote the development of 35-um pulsed fiber lasers but also open the photonic application of two-dimensional materials in this spectral region

Mode-locked thulium-doped fiber laser with chemical vapor deposited molybdenum ditelluride.

Abstract: A passively mode-locked thulium-doped fiber (TDF) laser was realized by employing chemical vapor deposited few-layer molybdenum ditelluride (MoTe2) as a saturable absorber (SA). The few-layer MoTe2 film was transferred onto the waist of a microfiber and then incorporated into a TDF laser with a typical all-fiber ring cavity configuration. Stable soliton pulses emitting at 1930.22 nm were obtained with a 3 dB bandwidth of 4.45 nm, a pulse duration of 952 fs, and an average power of 36.7 mW.

Tungsten diselenide for mode-locked erbium-doped fiber lasers with short pulse duration.

Abstract: In this paper, a WSe2 film prepared by chemical vapor deposition (CVD) is transferred onto a tapered fiber, and a WSe2 saturable absorber (SA) is fabricated. In order to measure the third-order optical nonlinearity of the WSe2, the Z-scan technique is applied. The modulation depth of the WSe2 SA is measured as being 21.89%. Taking advantage of the remarkable nonlinear absorption characteristic of the WSe2 SA, a mode-locked erbium-doped fiber laser is demonstrated at 1557.4 nm with a bandwidth of 25.8 nm and signal to noise ratio of 96 dB. To the best of our knowledge, the pulse duration of 163.5 fs is confirmed to be the shortest compared with previous mode-locked fiber lasers based on transition-metal dichalcogenides SAs. These results indicate that WSe2 is a powerful competitor in the application of ultrashort pulse lasers.

CVD-grown MoSe2 with high modulation depth for ultrafast mode-locked erbium-doped fiber laser.

Abstract: Two-dimensional materials have been widely used as optical modulator materials in mode-locked fiber lasers. In terms of the performance of the fiber laser, one with an ultrashort pulse and high stability has great commercial value. Herein, the MoSe2 grown by the chemical vapor deposition (CVD) method with high modulation depth, quality lattice structure and uniformity is successfully applied in a mode-locked erbium-doped fiber laser. The pulse duration and signal-to-noise ratio of the laser are 207 fs and 85 dB, respectively. The multifarious performance comparisons indicate that the CVD-based MoSe2 saturable absorber with the tapered fiber structure has unique advantages not only in the generation of ultrashort pulses, but also in the optimization of laser stability.

Tungsten diselenide for all-fiber lasers with the chemical vapor deposition method.

Abstract: Two-dimensional materials have become the focus of research for their photoelectric properties, and are employed as saturable absorption materials. Currently, the challenge is how to further improve the modulation depth of saturable absorbers (SAs) based on two-dimensional materials. In this paper, three kinds of WSe2 films with different thicknesses are prepared using the chemical vapor deposition method. The nonlinear optical responses of the WSe2 films including the nonlinear saturable absorption and nonlinear refractive index are characterized by the double-balanced detection method and Z-scan experiments. Different modulation depths are successfully obtained by controlling the thickness of the WSe2 films. We further incorporate them into an all-fiber laser to generate mode-locked pulses. The mode-locked fiber lasers with a pulse duration of 185 fs, 205.7 fs and 230.3 fs are demonstrated when the thickness of the WSe2 films is measured to be 1.5 nm, 5.7 nm and 11 nm, respectively. This work provides new prospects for WSe2 in ultrafast photonic device applications.

Dysprosium-doped ZBLAN fiber laser tunable from 2.8 μm to 3.4 μm, pumped at 1.7 μm.

Abstract: We demonstrate a mid-infrared dysprosium-doped fluoride fiber laser with a continuously tunable output range of 573 nm, pumped by a 1.7 μm Raman fiber laser. To the best of our knowledge, this represents the largest tuning range achieved to date from any rare-earth-doped fiber laser and, critically, spans the 2.8–3.4 μm spectral region, which contains absorption resonances of many important functional groups and is uncovered by other rare-earth ions. Output powers up to 170 mW are achieved, with 21% slope efficiency. We also discuss the relative merits of the 1.7 μm pump scheme, including possible pump excited-state absorption.

Ultrafast thulium fiber laser system emitting more than 1 kW of average power.

Abstract: In this Letter, we report on the generation of 1060 W average power from an ultrafast thulium-doped fiber chirped pulse amplification system. After compression, the pulse energy of 13.2 μJ with a pulse duration of 265 fs at an 80 MHz pulse repetition rate results in a peak power of 50 MW spectrally centered at 1960 nm. Even though the average heat-load in the fiber core is as high as 98 W/m, we confirm the diffraction-limited beam quality of the compressed output. Furthermore, the evolution of the relative intensity noise with increasing average output power has been measured to verify the absence of transversal mode instabilities. This system represents a new average power record for thulium-doped fiber lasers (1150 W uncompressed) and ultrashort pulse fiber lasers with diffraction-limited beam quality, in general, even considering single-channel ytterbium-doped fiber amplifiers.