Showing papers on "Fiber laser published in 2022"
01 Jul 2022
TL;DR: In this paper , a passively Q-switched er-doped fiber laser with two wavelength at 1530 nm and 1556 nm wavelength was designed based on the titanium disulfide (TiS2) saturable absorber, the ultra-fast modulator was fabricated with TiS2 by liquid-phase exfoliation and spin-coating methods and transferred onto a fiber ferrule.
Abstract: A passively Q-switched Er-doped fiber laser with two wavelength at 1530 nm and 1556 nm wavelength was designed based on the titanium disulfide (TiS2) saturable absorber, the ultra-fast modulator was fabricated with TiS2 by the liquid-phase exfoliation and spin-coating methods and transferred onto a fiber ferrule. In the experiment, two single-mode 980 nm pump sources were applied in order to detect the high damage threshold of TiS2. The shortest pulse duration and maximum output power of the stable self-starting Q-switched fiber laser are 1.45 µs and 3.93 mW, respectively. The adjustable range of the repetition rate is from 25.8 kHz to 126.8 kHz with about 100 kHz tuning range, and the pulse with energy up to 39.3 nJ. Our experimental results conclusively suggest that TiS2 nanocrystals were advanced nanomaterial with high damage threshold would have extensive application prospects in the field of pulse fiber lasers.
56 citations
TL;DR: In this article, NiO-MOF polyhedral particles are prepared by hydrothermal method and successfully applied to ultrafast photonics and achieved the 109th harmonic solitons in a compact mode-locked fiber laser at 1.55μm, the fiber laser has pulse duration of 766fs and repetition frequency of 413MHz.
Abstract: As a member of organic porous crystal structure, metal organic frameworks (MOFs) material has more unique properties due to its large specific surface area, high porosity, diversified structure and functions, it has been successfully applied in new energy, microelectronics, chemical reaction medical science and other fields. However, no study about NiO-MOF for the ultrafast optics application has been reported till now. In this paper, NiO-MOF polyhedral particles is prepared by hydrothermal method and successfully applied to ultrafast photonics. The modulation depth of NiO-MOF is 18.98 % through a dual-balance detection system. Most importantly, the 109th harmonic solitons are realized for the first time based on NiO-MOF in a compact mode-locked fiber laser at 1.55 μm, the fiber laser has pulse duration of 766 fs and repetition frequency of 413 MHz. As far as we know, this is the first time NiO-MOF has been applied to realize harmonic mode-locking at the fs level of more than 400 MHz. Due to the rich variability of MOFs structure, this study successfully provides support for the application of MOFs material in advanced photonics.
47 citations
TL;DR: In this article , the authors reviewed the recent advances on vector soliton in fiber lasers with emerging low-dimensional materials saturable absorber and classified them into 0-dimensional (0D), 1D, 2D, and other new materials.
32 citations
TL;DR: In this paper , a dual-wavelength-pumped all-fiber continuous-wave (CW) laser operating at 3.55 µm was reported, achieving an output power of 14.9 W, which is, to the best of our knowledge, a record.
Abstract: We report a dual-wavelength-pumped all-fiber continuous-wave (CW) laser operating at 3.55 µm that reached an output power of 14.9 W, which is, to the best of our knowledge, a record. The laser cavity, made of an erbium-doped fluoride fiber and bounded by two fiber Bragg gratings (FBGs), operates at an overall optical efficiency of 17.2% and a slope efficiency of 51.3% with respect to the 1976 nm launched pump power. The all-fiber design of the cavity not only allows for significant power scaling of the laser output, but also improves its long-term stability at high output power. The cavity design was set according to a numerical optimization that showed very good agreement with the experimental results.
23 citations
06 Mar 2022
TL;DR: In this article , the authors focus on realizing high-energy solid-state disk and slab systems and the nonlinear suppression strategies for high-power fiber systems using the functional fibers.
Abstract: High‐power laser sources are widely used in industrial precision processing and act as a new platform for strong‐field physics research using peak power over petawatt. This review focuses on realizing high‐energy solid‐state disk and slab systems and the nonlinear‐suppression strategies for high‐power fiber systems using the functional fibers. First, the implementations and enabling technologies of the solid‐state lasers for increasing peak power from gigawatt to petawatt are reviewed. Then the mechanisms and suppression strategies of the deterioration effects (including stimulated Raman scattering, stimulated Brillouin scattering, and transverse mode instability) in various fiber amplifiers are analyzed. At the same time, the mechanism and achievements of the current functional fibers are introduced. Finally, the challenges and perspectives of high‐power solid‐state and fiber amplifiers are summarized.
23 citations
TL;DR: In this article, the latest development of fiber-optic structures based on refractive index (RI) modification under fs-laser irradiation and their applications are reviewed. And then, the performances of RI-modified structures and their application are presented and compared.
Abstract: Femtosecond (fs) laser pulses direct writing technology has been extensively employed to achieve microfabrication in various optical fibers for a broad range of applications. In this paper, the latest development of fiber-optic structures based on refractive index (RI) modification under fs-laser irradiation and their applications are reviewed. Firstly, the processing mechanism of fs-laser direct writing for optical fiber RI modification is described. And then, the fiber-optic structures including various fiber gratings and interferometers based on RI modification are summarized. It shows that the fs-laser direct writing technology has great advantages in the fabrication of various fiber structures with excellent properties. Furthermore, the applications of these RI-modified fiber-optic structures in sensors, lasers, birefringence adjustable elements, and couplers are also discussed. To conclude, the performances of RI-modified structures and their applications are presented and compared.
22 citations
TL;DR: In this paper , a few-layer Ta4C3 MXene was developed through the liquid phase exfoliation (LPE) method, and it was inserted into an erbium-doped fiber laser (EDFL) cavity.
22 citations
TL;DR: In this article , the authors focus on the recent progress in continuous wave and pulsed mid-infrared fiber sources and the components that bring these laser sources closer to a field deployment as well as in industrial systems.
Abstract: Mid-infrared fiber sources, emitting between 2.5 µm and 5.0 µm, are interesting for their great potential in several application fields such as material processing, biomedicine, remote sensing and infrared countermeasures due to their high-power, their diffraction-limited beam quality as well as their robust monolithic architecture. In this review, we will focus on the recent progress in continuous wave and pulsed mid-infrared fiber lasers and the components that bring these laser sources closer to a field deployment as well as in industrial systems. Accordingly, we will briefly illustrate the potential of such mid-infrared fiber lasers through a few selected applications.
21 citations
TL;DR: In this paper , the authors highlight recent attractive research that adopted machine learning in the fiber laser field, including design and manipulation for on-demand laser output, prediction and control of nonlinear effects, reconstruction and evaluation of laser properties.
Abstract: Abstract In recent years, machine learning, especially various deep neural networks, as an emerging technique for data analysis and processing, has brought novel insights into the development of fiber lasers, in particular complex, dynamical, or disturbance-sensitive fiber laser systems. This paper highlights recent attractive research that adopted machine learning in the fiber laser field, including design and manipulation for on-demand laser output, prediction and control of nonlinear effects, reconstruction and evaluation of laser properties, as well as robust control for lasers and laser systems. We also comment on the challenges and potential future development.
20 citations
TL;DR: In this paper, a solid nanocomposite film is prepared by the drop-casting method where nanodiamond particles are embedded into polyvinylidene fluoride-trifluoroethylene (PVDF-TRFE).
Abstract: In this paper, we investigate nanodiamond (ND) particles as saturable absorber (SA) to produce Q-switched pulses in Erbium doped fiber laser (EDFL). The solid nanocomposite film is prepared by the drop-casting method where ND is embedded into polyvinylidene fluoride-trifluoroethylene (PVDF-TRFE) as a host polymer. Both physical and optical properties of the prepared film are experimentally demonstrated. To analyze the structure of fabricated ND-PVDF-TRFE film, various measurement methods are adopted. The ND-SA is positioned in the ring cavity of the EDFL to explore their abilities for generating stable Q-switched pulses. The results show that the fabricated ND-SA can generate stable laser pulses. Furthermore, the ND composite film proves that 10% of ND could be presented as an excellent promising material for various photonic applications. The Q-switched EDFL with 10% ND-SA began to self-start of stable Q-switch pulse at a saturated pump power of 59 mW with a 77.84 kHz repetition rate and pulse width of 4.34 μs. Besides, at a pump power of 187 mW, the Q-switched EDFL generates very stable pulses with a wavelength of 1558 nm, a repetition rate of 127.2 kHz, pulse duration of 1.565 μs, and an output power of 0.447 mW.
20 citations
TL;DR: In this article , the latest development of fiber-optic structures based on refractive index (RI) modification under femtosecond (fs) irradiation and their applications are reviewed.
Abstract: • Comprehensive literature review on femtosecond laser direct writing for refractive index modified fiber-optic structures. • Past existing works are only on fiber gratings or micro-cavities. • The fiber-optic structures including various fiber gratings and interferometers based on RI modification are summarized. • The applications of these RI-modified structures in sensors, lasers, birefringence elements, and couplers are discussed. Femtosecond (fs) laser pulses direct writing technology has been extensively employed to achieve microfabrication in various optical fibers for a broad range of applications. In this paper, the latest development of fiber-optic structures based on refractive index (RI) modification under fs-laser irradiation and their applications are reviewed. Firstly, the processing mechanism of fs-laser direct writing for optical fiber RI modification is described. And then, the fiber-optic structures including various fiber gratings and interferometers based on RI modification are summarized. It shows that the fs-laser direct writing technology has great advantages in the fabrication of various fiber structures with excellent properties. Furthermore, the applications of these RI-modified fiber-optic structures in sensors, lasers, birefringence adjustable elements, and couplers are also discussed. To conclude, the performances of RI-modified structures and their applications are presented and compared.
TL;DR: In this paper , the authors present a self-starting femtosecond all-fiber laser with the best energy and duration achieved to date, to the best of our knowledge.
Abstract: Mamyshev oscillators produce high-performance pulses, but technical and practical issues render them unsuitable for widespread use. Here we present a Mamyshev oscillator with several key design features that enable self-starting operation and unprecedented performance and simplicity from an all-fiber laser. The laser generates 110 nJ pulses that compress to 40 fs and 80 nJ with a grating pair. The pulse energy and duration are both the best achieved by a femtosecond all-fiber laser to date, to our knowledge, and the resulting peak power of 1.5 MW is 20 times higher than that of prior all-fiber, self-starting lasers. The simplicity of the design, ease of use, and pulse performance make this laser an attractive tool for practical applications.
TL;DR: In this article , the impact of signal bandwidth on the TMI threshold of fiber amplifiers has been investigated and the experimental results reveal that the threshold grows, keeps constant, and further grows as a function of spectral linewidth of seed lasers.
Abstract: In this work, we conduct a detailed experimental study on the impact of signal bandwidth on the TMI threshold of fiber amplifiers. Both the filtered superfluorescent fiber sources and the phase-modulated single-frequency lasers are employed to construct seed lasers with different 3 dB spectral linewidths ranging from 0.19 nm to 7.97 nm. The TMI threshold of the fiber amplifier employing those seed lasers are estimated through the intensity evolution of the signal laser, and different criteria have been utilized to characterize the spectral linewidth of the seed lasers. Notably, the experimental results reveal that the TMI threshold of fiber amplifiers grows, keeps constant, and further grows as a function of spectral linewidth of seed lasers. Our experimental results could provide a well reference to understand the mechanism of the TMI effect and optimize the TMI effect in high-power fiber amplifiers.
TL;DR: In this article , the authors reported efficient mid-IR laser emission from HBr-filled silica hollow-core fibres (HCFs) for the first time by pumping with a self-developed thulium-doped fiber amplifier seeded by several diode lasers over the range of 1940-1983 nm.
Abstract: Abstract Fibre lasers operating at the mid-IR have attracted enormous interest due to the plethora of applications in defence, security, medicine, and so on. However, no continuous-wave (CW) fibre lasers beyond 4 μm based on rare-earth-doped fibres have been demonstrated thus far. Here, we report efficient mid-IR laser emission from HBr-filled silica hollow-core fibres (HCFs) for the first time. By pumping with a self-developed thulium-doped fibre amplifier seeded by several diode lasers over the range of 1940–1983 nm, narrow linewidth mid-IR emission from 3810 to 4496 nm has been achieved with a maximum laser power of about 500 mW and a slope efficiency of approximately 18%. To the best of our knowledge, the wavelength of 4496 nm with strong absorption in silica-based fibres is the longest emission wavelength from a CW fibre laser, and the span of 686 nm is also the largest tuning range achieved to date for any CW fibre laser. By further reducing the HCF transmission loss, increasing the pump power, improving the coupling efficiency, and optimizing the fibre length together with the pressure, the laser efficiency and output power are expected to increase significantly. This work opens new opportunities for broadly tunable high-power mid-IR fibre lasers, especially beyond 4 μm.
TL;DR: In this paper, the authors review recent advances in the technology of writing fiber Bragg gratings (FBGs) in selected cores of multicore fibers by using femtosecond laser pulses.
Abstract: In this article, we review recent advances in the technology of writing fiber Bragg gratings (FBGs) in selected cores of multicore fibers (MCFs) by using femtosecond laser pulses. The writing technology of such a key element as the FBG opens up wide opportunities for the creation of next generation fiber lasers and sensors based on MCFs. The advantages of the technology are shown by using the examples of 3D shape sensors, acoustic emission sensors with spatially multiplexed channels, as well as multicore fiber Raman lasers. et al. Advances in femtosecond laser direct writing of fiber Bragg gratings in multicore fibers: technology, sensor and laser applications. Opto-Electron Adv 5 , 210055 (2022).
TL;DR: In this paper, the authors proposed a harmonic dual-wavelength (HDW) fiber laser based on graphene oxide (GO) and showed that Sb2Se3/GO SA can shorten the pulse width and increase the output power more effectively than GO, such as pulse width is shortened from 984fs to 511fs and the slope efficiency increased from 11.9% to 16.18% and 4.78% respectively.
Abstract: As new two-dimensional materials, antimony selenide (Sb2Se3) and graphene oxide (GO) are ideal photoelectric materials due to their appropriate band gap structure and strong light-matter interaction, which can be used in optical modulators, broadband ultrafast optical switches, and other photoelectric fields. The GO and Sb2Se3/GO measurements show excellent nonlinear characteristics with the modulation depth of 3.18% and 4.78%, respectively. This work proposes a harmonic dual-wavelength (HDW) fiber laser based on GO. This provides new possibilities for the research of ultrashort pulse sources with both high repetition frequency and multiple wavelengths. Furthermore, the conventional soliton mode-locking with 984 fs pulse width and soliton bundles mode-locking is obtained. The Sb2Se3/GO SA is coupled into the laser cavity for the first time to achieve higher performance mode-locked pulse. The results show that Sb2Se3/GO SA can shorten the pulse width and increase the output power more effectively than GO, such as the pulse width is shortened from 984 fs to 511 fs and the slope efficiency increased from 11.9% to 16.18%, which confirms its potential application in nonlinear optical material and ultrafast pulse generation. The results provide a new opportunity to apply traditional broadband nonlinear optical materials in ultrafast photonics and make a fundamental contribution to the development of advanced nanophotonic devices.
TL;DR: In this paper , a cladding-pumped Raman fiber laser (RFL) with less than 1% quantum defect was proposed and demonstrated, and the output power was scaled to 47.7 W with a QD of 1.29%.
Abstract: Abstract The quantum defect (QD) is an important issue that demands prompt attention in high-power fiber lasers. A large QD may aggravate the thermal load in the laser, which would impact the frequency, amplitude noise and mode stability, and threaten the security of the high-power laser system. Here, we propose and demonstrate a cladding-pumped Raman fiber laser (RFL) with QD of less than 1%. Using the Raman gain of the boson peak in a phosphorus-doped fiber to enable the cladding pump, the QD is reduced to as low as 0.78% with a 23.7 W output power. To our knowledge, this is the lowest QD ever reported in a cladding-pumped RFL. Furthermore, the output power can be scaled to 47.7 W with a QD of 1.29%. This work not only offers a preliminary platform for the realization of high-power low-QD fiber lasers, but also proves the great potential of low-QD fiber lasers in power scaling.
TL;DR: In this article , a nanodiamond (ND) particle was used as a saturable absorber to generate stable Q-switched pulses in Erbium doped fiber laser (EDFL).
Abstract: In this paper, we investigate nanodiamond (ND) particles as saturable absorber (SA) to produce Q-switched pulses in Erbium doped fiber laser (EDFL). The solid nanocomposite film is prepared by the drop-casting method where ND is embedded into polyvinylidene fluoride-trifluoroethylene (PVDF-TRFE) as a host polymer. Both physical and optical properties of the prepared film are experimentally demonstrated. To analyze the structure of fabricated ND-PVDF-TRFE film, various measurement methods are adopted. The ND-SA is positioned in the ring cavity of the EDFL to explore their abilities for generating stable Q-switched pulses. The results show that the fabricated ND-SA can generate stable laser pulses. Furthermore, the ND composite film proves that 10% of ND could be presented as an excellent promising material for various photonic applications. The Q-switched EDFL with 10% ND-SA began to self-start of stable Q-switch pulse at a saturated pump power of 59 mW with a 77.84 kHz repetition rate and pulse width of 4.34 μs. Besides, at a pump power of 187 mW, the Q-switched EDFL generates very stable pulses with a wavelength of 1558 nm, a repetition rate of 127.2 kHz, pulse duration of 1.565 μs, and an output power of 0.447 mW.
TL;DR: In this paper , the authors highlight recent attractive research that adopted machine learning in the fiber laser field, including design and manipulation for on-demand laser output, prediction and control of nonlinear effects, reconstruction and evaluation of laser properties.
Abstract: Abstract In recent years, machine learning, especially various deep neural networks, as an emerging technique for data analysis and processing, has brought novel insights into the development of fiber lasers, in particular complex, dynamical, or disturbance-sensitive fiber laser systems. This paper highlights recent attractive research that adopted machine learning in the fiber laser field, including design and manipulation for on-demand laser output, prediction and control of nonlinear effects, reconstruction and evaluation of laser properties, as well as robust control for lasers and laser systems. We also comment on the challenges and potential future development.
TL;DR: In this article, a wavelength-interval-switchable multi-wavelength thulium-doped fiber laser (MWTDFL) is proposed and demonstrated, based on a nonlinear dual-pass Mach-Zehnder interferometer (NDP-MZI) filter for the first time.
Abstract: A wavelength-interval-switchable multi-wavelength thulium-doped fiber laser (MWTDFL) is proposed and demonstrated, based on a nonlinear dual-pass Mach-Zehnder interferometer (NDP-MZI) filter for the first time. We investigate the NDP-MZI filter theoretically and experimentally, which has both the transmission characteristics of a dual-pass Mach-Zehnder interferometer (DP-MZI) for wavelength selection and a nonlinear optical loop mirror (NOLM) for suppressing wavelength competition. By tuning two polarization controllers (PCs), two 20-wavelength operations with an opposite phase and a same wavelength-interval of 0.46 nm are obtained and switched between each other flexibly. The maximum power fluctuation and wavelength drift measured are 0.612 dB and 0.04 nm, respectively. In addition, due to the power-equalizing effect resulting from the NOLM, 60 lasing wavelengths within a 3-dB bandwidth with an adjacent wavelength-interval of 0.23 nm are also obtained by adjusting the PCs carefully, and the stability of the MWTDFL is measured experimentally. Furthermore, the performance of the NDP-MZI using an 80 m highly nonlinear fiber has been studied in detail as well. The proposed MWTDFL may find great applications in optical communication and optical sensing.
TL;DR: Process optimization indicates that while operating with laser processing parameters resulting in the highest MRR, the best ratio between the MRR and surface roughness appears at ~50% overlap of the laser pulses, regardless of the material being processed.
Abstract: In this paper, we investigate the influence of the following parameters: pulse duration, pulse repetition rate, line-to-line and pulse-to-pulse overlaps, and scanning strategy on the ablation of AISI 316L steel and CuZn37 brass with a nanosecond, 1064-nm, Yb fiber laser. The results show that the material removal rate (MRR) increases monotonically with pulse duration up to the characteristic repetition rate (f0) where pulse energy and average power are maximal. The maximum MRR is reached at a repetition rate that is equal or slightly higher as f0. The exact value depends on the correlation between the fluence of the laser pulses and the pulse repetition rate, as well as on the material properties of the sample. The results show that shielding of the laser beam by plasma and ejected material plays an important role in reducing the MRR. The surface roughness is mainly influenced by the line-to-line and the pulse-to-pulse overlaps, where larger overlap leads to lower roughness. Process optimization indicates that while operating with laser processing parameters resulting in the highest MRR, the best ratio between the MRR and surface roughness appears at ~50% overlap of the laser pulses, regardless of the material being processed.
TL;DR: In this article , the optical performance of passively mode-locked pulses in erbium-doped fiber laser incorporating gold-nanoparticles (Au-NPs) as a saturable absorber (SA) was demonstrated.
Abstract: We demonstrate the optical performance of passively mode-locked pulses in erbium-doped fiber laser incorporating gold-nanoparticles (Au-NPs) as a saturable absorber (SA). Au-NPs of diameters between 5 to 15 nm were synthesized using the pulsed laser ablation method and blended with polydimethylsiloxane polymer. The resulting nanocomposite was deposited on the tapered region of a microfiber with a spin-coating method. The proposed Au-NPs SA recorded a modulation depth of 0.4% and low saturation intensity of 0.1 MW/cm2 leading to stable mode-locking operation in the erbium-doped fiber laser cavity at a low threshold pump power of about 45.6 mW. A mode-locked pulse train with a duration of 933 fs, pulse repetition rate of 6.25 MHz, and peak-to-pedestal extinction ratio of 54.1 dB was achieved at a pump power of 168.1 mW. The obtained results demonstrate that the spherical Au-NPs synthesized by pulsed laser ablation is a feasible material for SA fabrication, validating its saturable absorption properties in a 1.55 μm wavelength region.
TL;DR: In this article , an all-fiberized and narrow-linewidth fiber amplifier with record output power and near-diffraction-limited beam quality is presented, and the practical power limit is estimated through the maximum output powers of the fiber amplifier employing unidirectional pumping schemes.
Abstract: Abstract In this work, an all-fiberized and narrow-linewidth fiber amplifier with record output power and near-diffraction-limited beam quality is presented. Up to 6.12 kW fiber laser with the conversion efficiency of approximately 78.8% is achieved through the fiber amplifier based on a conventional step-index active fiber. At the maximum output power, the 3 dB spectral linewidth is approximately 0.86 nm and the beam quality factor is Mx2 = 1.43, My2 = 1.36. We have also measured and compared the output properties of the fiber amplifier employing different pumping schemes. Notably, the practical power limit of the fiber amplifier could be estimated through the maximum output powers of the fiber amplifier employing unidirectional pumping schemes. Overall, this work could provide a good reference for the optimal design and potential exploration of high-power narrow-linewidth fiber laser systems.
TL;DR: In this article , the authors presented a mode-locked ytterbium-doped fiber laser (YDFL) using their home-made topological insulator Bi2Se3 nanosheets as the saturable absorber.
Abstract: Fiber lasers have long remained relevant for various applications worldwide in many industries. This paper presents a mode-locked ytterbium-doped fiber laser (YDFL) using our home-made topological insulator Bi2Se3 nanosheets (TI Bi2Se3) as the saturable absorber. The fabricated TI Bi2Se3 is transported to the end of the fiber ferrule using an optical deposition process, which is a key ingredient for initiating a pulsed fiber laser. With a pump power of 211.1 mW, the captured repetition rate and pulse width are 8.3 MHz and 6.2 ns, respectively. The length of the setup configuration is approximately 20 m, which corresponds to an output power measurement of 12.4 mW with a calculated pulse energy of 1.5 nJ. There are no significant Kelly sidebands, but the strong stability of the pulsed laser is defined by a high signal-to-noise ratio (SNR) of around 60.35 dB.
TL;DR: In this paper , the effect of laser power and laser spot diameter on the eruption of spatter particles was investigated. And the relationship between spatter eruption and the mass loss of the weld-seam was revealed.
Abstract: • Effect of fiber laser density on the eruption characteristics of spatter particles were observed. • The relationship between the spatter eruption and the mass loss of the weld-seam are revealed. • Effects of fiber laser density on the inclination angle of the FKW was investigated. • Effect reasons of fiber laser density on spatters eruption are revealed. • The results are of great significance for optimizing the fiber laser keyhole welding process. Violent eruption of spatters is one of the major problems restricting fiber laser keyhole welding technology development. In this study, the fiber laser power density variation was attained by altering the laser power and laser spot diameter for analyzing its impact on the eruption of spatters. The severity of spatters’ eruption can be indicated by the number of spatters and the mass loss of the weld seam. The correlation between the number of spatters and laser power density can be positive (if the latter is adjusted by changing the laser power) or negative (if the laser power density is varied by changing the laser spot diameter). When the latter diameter is changed, it has a strong impact on the vapor induced by the laser on the front keyhole wall (FKW), the FKW inclination angle, and the molten pool surface tension. The number of spatters also positively correlates with the laser-induced vapor on the FKW or the molten pool width and negatively correlates with the FKW inclination angle. Reducing the laser spot diameter can increase the laser power density, enhancing the welding process stability and suppressing the eruption of spatters to a certain extent.
TL;DR: In this article, the laser power density variation was attained by altering laser power and laser spot diameter for analyzing its impact on the eruption of spatters and mass loss of the weld seam.
Abstract: Violent eruption of spatters is one of the major problems restricting fiber laser keyhole welding technology development. In this study, the fiber laser power density variation was attained by altering the laser power and laser spot diameter for analyzing its impact on the eruption of spatters. The severity of spatters’ eruption can be indicated by the number of spatters and the mass loss of the weld seam. The correlation between the number of spatters and laser power density can be positive (if the latter is adjusted by changing the laser power) or negative (if the laser power density is varied by changing the laser spot diameter). When the latter diameter is changed, it has a strong impact on the vapor induced by the laser on the front keyhole wall (FKW), the FKW inclination angle, and the molten pool surface tension. The number of spatters also positively correlates with the laser-induced vapor on the FKW or the molten pool width and negatively correlates with the FKW inclination angle. Reducing the laser spot diameter can increase the laser power density, enhancing the welding process stability and suppressing the eruption of spatters to a certain extent.
TL;DR: In this paper , a Raman distributed temperature sensor based on standard telecom single mode fibers and efficient polarization-independent superconducting nanowire single photon detectors is presented, which shows 3 cm and 1.5 cm resolution on a 5 m fiber upon one minute integration.
Abstract: We present a Raman distributed temperature sensor based on standard telecom single mode fibers and efficient polarization-independent superconducting nanowire single photon detectors. Our device shows 3 cm and 1.5 °C resolution on a 5 m fiber upon one minute integration. We show that spatial resolution is limited by the laser pulse width and not by the detection system. Moreover, for long fibers the minimum distance for a measurable temperature step change increases of around 4 cm per km length, because of chromatic dispersion at the Stokes and Anti-Stokes wavelengths. Temperature resolution is mainly affected by the drop in the laser repetition rate when long fibers are tested. On a 500 m fiber, a trade-off of 10 cm and 8 °C resolution is achieved with 3 minutes integration. Fiber-based distributed temperature sensing, combining centimetric spatial resolution with hundreds of meters sensing range, could pave the way for a new kind of applications, such as 2D and 3D temperature mapping of complex electronic devices, particles detectors, cryogenic and aerospace instrumentation.
TL;DR: In this paper , the authors proposed a harmonic dual-wavelength (HDW) fiber laser based on graphene oxide (GO) and showed that Sb2Se3/GO SA can shorten the pulse width and increase the output power more effectively than GO, such as pulse width is shortened from 984 fs to 511 fs and the slope efficiency increased from 11.9% to 16.18% and 4.78% respectively.
Abstract: As new two-dimensional materials, antimony selenide (Sb2Se3) and graphene oxide (GO) are ideal photoelectric materials due to their appropriate band gap structure and strong light-matter interaction, which can be used in optical modulators, broadband ultrafast optical switches, and other photoelectric fields. The GO and Sb2Se3/GO measurements show excellent nonlinear characteristics with the modulation depth of 3.18% and 4.78%, respectively. This work proposes a harmonic dual-wavelength (HDW) fiber laser based on GO. This provides new possibilities for the research of ultrashort pulse sources with both high repetition frequency and multiple wavelengths. Furthermore, the conventional soliton mode-locking with 984 fs pulse width and soliton bundles mode-locking is obtained. The Sb2Se3/GO SA is coupled into the laser cavity for the first time to achieve higher performance mode-locked pulse. The results show that Sb2Se3/GO SA can shorten the pulse width and increase the output power more effectively than GO, such as the pulse width is shortened from 984 fs to 511 fs and the slope efficiency increased from 11.9% to 16.18%, which confirms its potential application in nonlinear optical material and ultrafast pulse generation. The results provide a new opportunity to apply traditional broadband nonlinear optical materials in ultrafast photonics and make a fundamental contribution to the development of advanced nanophotonic devices.
TL;DR: In this paper , a semiconductor saturable absorber mirror mode-locked Tm:(Lu,Sc)2O3 ceramic laser in-band pumped by a Raman fiber laser at 1627 nm is presented.
Abstract: We report on a semiconductor saturable absorber mirror mode-locked Tm:(Lu,Sc)2O3 ceramic laser in-band pumped by a Raman fiber laser at 1627 nm. The nonlinear refractive index (n2) of the Tm:(Lu,Sc)2O3 ceramic has been measured to be 4.66 × 10-20 m2/W at 2000 nm. An average output power up to 1.02 W at 2060 nm is achieved for transform-limited 280-fs pulses at a repetition rate of 86.5 MHz, giving an optical efficiency with respect to the absorbed pump power of 36.4%. Pulses as short as 66 fs at 2076 nm are produced at the expense of output power (0.3 W), corresponding to a spectral bandwidth of 69 nm. The present work reveals the potential of Tm3+-doped sesquioxide transparent ceramics for power scaling of femtosecond mode-locked bulk lasers emitting in the 2-µm spectral range.
TL;DR: In this article , the authors reported efficient mid-IR laser emission from HBr-filled silica hollow-core fibres (HCFs) for the first time by pumping with a self-developed thulium-doped fiber amplifier seeded by several diode lasers over the range of 1940-1983 nm.
Abstract: Abstract Fibre lasers operating at the mid-IR have attracted enormous interest due to the plethora of applications in defence, security, medicine, and so on. However, no continuous-wave (CW) fibre lasers beyond 4 μm based on rare-earth-doped fibres have been demonstrated thus far. Here, we report efficient mid-IR laser emission from HBr-filled silica hollow-core fibres (HCFs) for the first time. By pumping with a self-developed thulium-doped fibre amplifier seeded by several diode lasers over the range of 1940–1983 nm, narrow linewidth mid-IR emission from 3810 to 4496 nm has been achieved with a maximum laser power of about 500 mW and a slope efficiency of approximately 18%. To the best of our knowledge, the wavelength of 4496 nm with strong absorption in silica-based fibres is the longest emission wavelength from a CW fibre laser, and the span of 686 nm is also the largest tuning range achieved to date for any CW fibre laser. By further reducing the HCF transmission loss, increasing the pump power, improving the coupling efficiency, and optimizing the fibre length together with the pressure, the laser efficiency and output power are expected to increase significantly. This work opens new opportunities for broadly tunable high-power mid-IR fibre lasers, especially beyond 4 μm.