Showing papers in "Optics and Laser Technology in 2022"
TL;DR: In this article, the fundamental difficulties and latest developments in dissimilar laser welding of steel-copper, steel-aluminum, aluminum-coppers, and steel-nickel are reviewed.
Abstract: The electric vehicle (EV) battery systems are complex assemblies of dissimilar materials in which battery cells are connected using several thousand interconnect joints. Every single joint influences the functionality and efficiency of the whole battery system, making the joining process crucial. Laser welding is considered a desirable choice for EV battery manufacturing due to its non-contact nature, high energy density, precise control over the heat input, and ease of automation. However, incompatible thermos-physical properties of dissimilar materials used in battery tabs and interconnectors pose a significant challenge for achieving complete metallurgical bond. Furthermore, the formation of undesirable weld microstructures such as hard and brittle intermetallic compounds (IMCs) substantially undermines the structural, electrical, and thermal characteristics of battery joints. This paper reviews the fundamental difficulties and latest developments in dissimilar laser welding of steel-copper, steel-aluminum, aluminum-copper, and steel-nickel, some of the potential joint combinations in EV battery pack manufacturing. The weld microstructure and common metallurgical defects, as well as mechanical and electrical properties of joints are discussed. In addition, the effects of laser welding process parameters on the joint properties and the applicability of various interlayers and coatings in laser welding of battery materials are assessed.
65 citations
TL;DR: In this paper , a hybrid experimental and computational model is developed to estimate the absorption ratio of the laser for Laser-Based Powder Bed Fusion (LB-PBF) of IN718, and two test sets for the initial test with constant and dynamic/(process parameters dependent) absorption ratios were simulated.
Abstract: The purpose of this research is to develop a hybrid experimental and computational model to estimate the absorption of the laser for Laser-Based Powder Bed Fusion (LB-PBF) of IN718. The research also aims to find an underlying knowledge on the effect of absorption ratio on meltpool morphology. This model helps to improve the accuracy of the prediction of the meltpool morphology and the rheology of the melt tracks as well as the temperature-related phenomena in the process. In this paper, two test sets for the initial test with constant and dynamic/(process parameters dependent) absorption ratios were simulated. Melt tracks with different process parameters are printed and simulated from low to high energy density. Then, the Absorption Ratio (AR) is changed for each simulation until the same meltpool depth as the experimental results is obtained. In the next step, the temperature of the meltpool in the interaction area of the laser and material is measured from the performed simulations. Based on the obtained temperature and process parameters, a mathematical model is developed to estimate the absorption ratio in different conditions. The model is validated in hybrid computational and experimental conditions. The investigation provides the first model to calculate the absorption ratio in LB-PBF based on the temperature of the meltpool and process parameters. Results show that the developed model significantly enhances the accuracy of estimating meltpool features such as temperature, rheological and thermophysical properties of the material in the melting state.
65 citations
TL;DR: In this paper, the propagation properties of all-dielectric metamaterials (ADMs) based on a SiO2-Si asymmetric hybrid block, including the effects of structural parameters, asymmetrical degrees, carrier doping concentrations, and graphene Fermi levels, were investigated.
Abstract: We investigated the propagation properties of all-dielectric metamaterials (ADMs) based on a SiO2-Si asymmetric hybrid block, including the effects of structural parameters, asymmetrical degrees, carrier doping concentrations, and graphene Fermi levels. The Q-factor of Fano resonance reaches more than 270, and the amplitude modulation depth (MD) is about 75% if the asymmetric degree changes in the range of 2–10 μm. The carrier concentration of silicon significantly affects the intensity of excited Fano resonance. When the carrier concentration of Si is 1 × 1014 cm−3, the excited Fano resonance is the strongest, and the transmission peak is about 0.92. With the help of a uniform graphene layer, the Fano resonance can be effectively modulated, the frequency MD is about 20% if the Fermi level changes in the scope of 0.01–0.3 eV. These results can help us to design THz high Q-factor devices, such as sensors, filters, and modulators.
58 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 , an energy-conservation deep-learning (ECDL) method was used to predict the formation mechanism of vector solitons in birefringent fibers. But, the method is not suitable for high-dimensional optical networks.
Abstract: • The ECDL method integrates seamlessly data and mathematical physics models, even in partially understood, uncertain and high-dimensional contexts. • The ECDL method makes the predicted solution of physical model more consistent. • The ECDL method is effective for inverse problems and predicting the formation mechanism of vector solitons. The energy conservation law is introduced into a loss function of the physics-informed neural network (PINN), and an energy-conservation deep-learning (ECDL) method is constructed to study a coupled nonlinear Schrödinger equation (CNLSE). Using the ECDL method, we analyze the formation mechanism of vector solitons in birefringent fibers, and predict the dynamic behaviors of vector solitons, including one-soliton, two-soliton interaction, soliton molecule, rogue wave, and nondegenerate soliton. The related physical processes such as the energy conversion and power conservation along the propagation of soliton are studied. The results show that the nonlinear and dispersive effects separately cause the pulse broadening in time and frequency domains. The energy, shape and velocity of pulse in the transmission process remain unchanged when the two effects are balanced. Compared with the PINN method, the ECDL has higher accuracy and good generalization ability for a variety of soliton pulse propagation scenarios in optical fiber. Therefore, the deep learning method based on the prior knowledge of energy conservation is an effective tool to promote the research of nonlinear optics.
46 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 1.55 μm, the fiber has pulse duration of 766 fs and repetition frequency of 413 MHz.
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.
45 citations
TL;DR: In this article, a comprehensive state-of-the-art review for LC-HEA-based coatings, focusing on the use of laser deposition technique for HEAs, the effect of laser process parameters on mechanical properties, and microstructural evolution are discussed, with regard to their microstructure and phase composition.
Abstract: Since the advent in 2004, high-entropy alloys (HEAs) have become an attraction for the world and applied in the extensive engineering fields due to their outstanding properties. These materials are exhibiting their potentiality for challenging conditions where coatings are applied through laser deposition technology. Laser deposition techniques containing laser cladding (LC), laser surface alloying (LSA), and laser surface remelting (LSR) are the modern technologies that can be applied for surface modification through HEAs. Nobler properties of the LC-HEA depositions over the conventional alloys have further explored this field in the last few years. Here, this paper provides a comprehensive state-of-the-art review for LC-HEA-based coatings, focusing on the use of laser deposition technique for HEAs, the effect of laser process parameters on mechanical properties, and microstructural evolution. The mechanical characteristics include but are not limited to hardness, wear, corrosion, and erosion resistance are discussed, with regard to their microstructure and phase composition. Besides, the existing problems, possible future developments regarding the LC-HEA depositions are predicted. Due to excellent mechanical properties and functional potential as well as a variety of element constitutions for HEA designing, laser-assisted depositions containing blended HEAs as feedstock material will have promising applications prospects in the field of material science and engineering.
42 citations
TL;DR: In this article , an efficient and ultra-broadband solar absorber is proposed, which is composed of periodic nano-disk combination array on TiO2 thin film, and the authors used FDTD solutions to simulated and calculated the field distribution, absorption spectrum and thermal radiation intensity of the structure.
Abstract: Solar energy is a widely used clean energy source, and solar absorber with wider spectrum and higher efficiency is more ideal for various applications of solar energy. In this paper, an efficient and ultra-broadband solar absorber is proposed, which is composed of periodic nano-disk combination array on TiO2 thin film. In our work, we use FDTD solutions to simulated and calculated the field distribution, absorption spectrum and thermal radiation intensity of the structure to explore the physical mechanism of the resonator. Among them, the resonance between the polarization direction of the three-layer nano-disk and the plasmon resonance at the junction of TiN nano-disk and TiO2 have obtained the ultra-broadband high-efficiency absorption of the absorber. The absorption bandwidth (A > 90%) reaches 1869 nm (288.5 nm-2157.5 nm), the average absorption efficiency in this range is 96.56%, and the average absorption efficiency in the whole wave band (200–2600 nm) is 93.77%. In addition, the structure has extremely strong heat radiation intensity, with high emission efficiency of 92.83% at 1500 K. Furthermore, the solar absorber proposed by us is polarization independent. In Transverse Electric (TE) mode and Transverse Magnetic (TM) mode, the increase of incident angle causes slight spectral shift of absorption spectrum, and the maximum deviation of average absorption efficiency is 2.17%. Ultra-broad absorption band, high absorption efficiency, high radiation intensity and polarization independence make it competent for thermo-photovoltaics and other high-power optoelectronic, radiation energy and information collection processes.
42 citations
TL;DR: In this paper , a novel approach is proposed to produce flexible transparent EMI shielding film with silver mesh based on electric-field-driven (EFD) microscale 3D printing.
Abstract: In order to address the challenging issue regarding the high-efficiency and low-cost fabrication of high-performance flexible transparent electromagnetic interference (EMI) shielding films, a novel approach is proposed to produce flexible transparent EMI shielding film with silver mesh based on electric-field-driven (EFD) microscale 3D printing. The manufacturing principle and the reasonable process parameters are revealed with a series of experiments. Following this fabricating scheme and self-developed EFD micro-scale 3D printer, three flexible transparent EMI shielding films having a size of 60 mm × 60 mm and a line width of 26 μm are achieved utilizing the low-temperature nano silver paste (75% silver content and 350 dPa·s (25 °C) dynamic viscosity). The experimental result shows that the adhesive force between the sintered silver mesh and the polyethylene terephthalate (PET) substrate is measured to be 5B with 3 M scotch tape. The bending experiment proves the excellent mechanical flexibility of the flexible transparent EMI shielding film. In different chemical environments and ultrasonic vibration environments, the silver mesh flexible transparent EMI shielding film can still maintain good electrical properties. When the pitch of the silver mesh is 500 μm, the optical transmittance is 90.5% and the EMI shielding efficiency for the common medium-high frequency electromagnetic wave is greater than 26 dB. When the pitch is 300 μm, the optical transmittance is 84% and the shielding efficiency is higher than 32 dB. When the pitch is 150 μm, the optical transmittance is 69% and the shielding efficiency is higher than 34 dB. As a result, the proposed method provides a promising solution for mass producing high-performance silver mesh flexible transparent EMI shielding films at low cost and high throughput.
35 citations
TL;DR: Wang et al. as discussed by the authors proposed a new image encryption scheme by combining six-dimensional non-degenerate discrete hyper-chaotic system, two-dimensional discrete cosine Stockwell transform with DNA-level modulus diffusion.
Abstract: • An image encryption scheme with 2D discrete cosine Stockwell transform and DNA-level modulus diffusion is proposed. • The 2D discrete cosine Stockwell transform performs better in image compression and anti-noise. • The improved global chaotic diffusion algorithm achieves a better diffusion effect. A new image encryption scheme is presented by combining six-dimensional non-degenerate discrete hyper-chaotic system, two-dimensional discrete cosine Stockwell transform with DNA-level modulus diffusion. The significant advantages of this scheme are the large key space, strong anti-noise ability and resistance to common attacks. To resist the powerful chosen plaintext attack, the initial conditions of the chaotic systems are generated with the SHA-512 hash function value of the plaintext image and the external key. The transmission burden is reduced by compressing the original image with the two-dimensional discrete cosine Stockwell transform. Then random DNA encoding is performed on the compressed image to obtain the DNA image. To speed up the encryption, the DNA-level modulus diffusion algorithm is designed to scramble and diffuse pixels at the same time. Finally, the final encrypted image is obtained by re-encrypting the diffused DNA image with the bit-level permutation and the improved global dynamic diffusion. The two high-dimensional chaotic systems introduced in the image encryption scheme greatly increases the key space and then the image encryption scheme can resist the brute-force attack. The presented scheme is sensitive to both plaintext images and secret keys. Simulation results show that the proposed image encryption algorithm is feasible, secure and effective.
34 citations
TL;DR: In this article , a finite element method-based investigation of preheating and in-situ rescanning techniques during selective laser melting of 316L stainless steel is presented.
Abstract: • The influence of preheating techniques on the resultant modifications in residual stress profile of SLM fabricated components was investigated. • Powder bed preheating and baseplate pre heating techniques in SLM were compared for a wide range of temperatures. • In-situ rescanning was also observed as a possible reduction technique for residual stresses in SLM fabricated components. • Relationships between rescanning parameters and the residual stress profile were also established. The premature fractures, cracks, distortions, and delamination in selective laser melting manufactured components are among the most prominent challenges. These issues in selective laser melting manufactured components restrict their widespread application. Residual stresses are among the most common reasons for these behaviors. Post processing techniques are therefore used for most of the selective laser melting fabricated components to either eliminate or decrease these stresses. However, this increases the production time and fabrication costs. Therefore, in process techniques to reduce these residual stresses are of paramount importance in promoting the largescale production of metallic components. In this paper, a finite element method-based investigation of preheating and in-situ rescanning techniques during selective laser melting of 316L stainless steel is presented. The influence of various preheating temperatures on the final residual stress profile was observed. Similarly, the variations in residual stresses with different rescanning parameters were also investigated. Both baseplate and powder bed preheating procedures were observed to have considerable effects on the residual stresses. The residual stresses were significantly decreased with increasing preheating temperatures. Baseplate and powder bed preheating at 400 °C were observed to have decreased the residual stresses from 353.57 MPa (stress values without preheating or rescanning) to 27 MPa and 30 MPa, respectively. In-situ rescanning was also observed to be beneficial in decreasing the stresses in SLM fabricated components. However, their influence is relatively smaller in comparison with the preheating. No significant influence of rescanning on the stress distribution was also observed.
TL;DR: In this article , a 2 × 1 multiplexer is designed and simulated based on two-dimensional photonic crystals with a cubic lattice, where only linear defects were considered in the design of the structure.
Abstract: • A new design for optical multiplexer has been proposed based on photonic crystals. • A small structure is used for the proposed optical 2 × 1 multiplexer. • The simplicity of the structure makes it suitable for optically integrated circuits. Photonic crystals are alternating structures widely used to design various types of logic circuits. In this paper, a 2 × 1 multiplexer is designed and simulated based on two-dimensional photonic crystals with a cubic lattice. Silicon rods in the air were used to design this multiplexer. Only linear defects were considered in the design of the structure. In other words, none of the rods were changed and all Si rods were the same, which is one of the advantages of this structure. Optical sources with a wavelength of 1.55 µm were utilized in the inputs and select line. The size of the structure was 12.16 µm × 12.16 µm. The small dimension and the simplicity of the structure make it a suitable candidate in optically integrated circuits.
TL;DR: In this article, two medium-entropy alloy coatings (MEACs), CoCrNiTi and CrFeNiTi, were successfully prepared on pure Ti sheet by utilizing pulsed laser cladding.
Abstract: Two medium-entropy alloy coatings (MEACs), CoCrNiTi and CrFeNiTi, were successfully prepared on pure Ti sheet by utilizing pulsed laser cladding. Microstructural characterization reveals that both the MEACs are mainly comprised of BCC solid-solution phase along with interdendritic Cr2Ti Laves phase (C14 type) due to element segregation. Hardness and wear tests show that the CoCrNiTi MEAC has a hardness of 762 ± 32 HV and a specific wear rate of 1.7 × 10−5 mm3·N−1·m−1, and those of the CrFeNiTi MEAC are 820 ± 34 HV and 2.8 × 10−5 mm3·N−1·m−1, respectively, both of which are markedly superior to the pure Ti substrate (114 ± 5 HV and 5.4 × 10−4 mm3·N−1·m−1). Comprehensive analyses suggest that the excellent properties of the MEACs can be attributed to combined strengthening effects of solid-solution, short-range order, grain refinement and the Cr2Ti Laves phase.
TL;DR: In this paper, Fe-Co-B-Si-Nb amorphous coatings were deposited on 45 medium carbon steel under different scanning speeds by high-speed laser cladding technology.
Abstract: Fe-Co-B-Si-Nb amorphous coatings were deposited on 45 medium carbon steel under different scanning speeds by high-speed laser cladding technology. The results showed that the surface roughness of the coating became lower and the surface of the coating became smoother with the increase in scanning speed. In addition, the residual tensile stress and the thermal expansion coefficient decreased with the increase in the scanning speed. When the scanning speed was 80.38 m/min, the residual tensile stress was 106.13 ± 24.03 MPa. The residual stress was reduced by more than 50% compared with the scanning speed of 37.68 m/min. The XRD and TEM observation results of the coating at the scanning speed of 80.38 m/min showed a large volume fraction of amorphous phase and some crystalline dendrites. Under the scanning speed of 80.38 m/min, the cooling rate at the top of the coating could reach 1.08 × 105 °C/s, which greatly increased the amorphous formation ability. The hardness and wear resistance properties of the coating were also tested and analyzed. Better performance of the coatings was obtained when the scanning speed was higher.
TL;DR: In this paper , the basic principles and characteristics of the combined pulse laser (CPL) processing method are systematically introduced, and how the CPL method is for precisely and efficiently ablating, drilling, welding and structuring.
Abstract: With wide applicability and low-cost processing advantages, laser processing, as a mature and versatile tool, is forming an alternative to conventional processing technologies. In recent years, the global laser market ushered in a broad new demand since the gradual increase in the penetration rate of laser processing in consumer electronics, automotive processing, aerospace, medical and other fields. Ultrafast laser and continuous wave (CW) laser are the representatives of high-quality and high-efficiency in laser processing, respectively, but it is a huge challenge to achieve high-quality and high-efficiency laser processing at the same time in the true sense, which has been the goal of the joint efforts of scientific researchers in recent decades. In this context, combined pulse laser (CPL), one of the hybrid laser processing technologies, has proven to be a reliable tool for the high-quality and high-efficiency processing through the processing advantages of different types of lasers and controlling the laser-matter interaction. In this review, the basic principles and characteristics of the CPL processing method are systematically introduced. Also, how the CPL method is for precisely and efficiently ablating, drilling, welding and structuring and their recent advancements are analyzed. Finally, a summary and outlook of the CPL technology is highlighted.
TL;DR: In this paper , a comprehensive review about polymer optical fiber for human physiological and body functions monitoring, namely mechanisms, materials, and applications, is presented, which makes it possible to envisage a widespread implementation of such sensors in this research field in the next few years.
Abstract: • Polymer optical fibers have several advantages for healthcare applications. • Novel polymer optical fibers give new opportunity for optical fiber sensing technology. • Overview about polymer optical fibers for monitoring human physiological and body function. • A comprehensive review from mechanisms, materials to applications. The monitoring of human physiological signs and body functions, such as respiration rate, heart rate, foot pressure, and joint movement, plays an important role in medical advances and life quality improvements. Polymer optical fibers are made of polymer materials with attractive characteristics compared with silica fibers, such as low Young’s modulus, high failure strain levels, high flexibility, and bio-compatibility. These advantages are well-aligned with the instrumentation requirements for monitoring human physiological and body functions. In this perspective, this paper provides a comprehensive review about polymer optical fiber for human physiological and body functions monitoring, namely mechanisms, materials, and applications, which makes it possible to envisage a widespread implementation of such sensors in this research field in the next few years.
TL;DR: A comprehensive review about polymer optical fiber for human physiological and body functions monitoring, namely mechanisms, materials, and applications, has been provided in this paper, which makes it possible to envisage a widespread implementation of such sensors in this research field in the next few years.
Abstract: The monitoring of human physiological signs and body functions, such as respiration rate, heart rate, foot pressure, and joint movement, plays an important role in medical advances and life quality improvements. Polymer optical fibers are made of polymer materials with attractive characteristics compared with silica fibers, such as low Young’s modulus, high failure strain levels, high flexibility, and bio-compatibility. These advantages are well-aligned with the instrumentation requirements for monitoring human physiological and body functions. In this perspective, this paper provides a comprehensive review about polymer optical fiber for human physiological and body functions monitoring, namely mechanisms, materials, and applications, which makes it possible to envisage a widespread implementation of such sensors in this research field in the next few years.
TL;DR: In this article , the effects of employing an S-curve laser power which is distributed along the laser oscillating path (sine wave) to improve the microstructure and mechanical properties of the joints were investigated.
Abstract: • A S-curve power of laser oscillating welding is proposed. • The grains in the welded joint with S-curve power were refined, and the mechanism of grain refinement is analyzed. • Compared with joints with constant power, the tensile strength with S-curve laser power was increased by 35.3% and could reach 99.1% of the base metal strenght. Laser oscillating welding of 5A06 aluminum alloy is widely used in industry. In order to improve the performance of Al-based welded joints and reduce welding defects, this paper details the effects of employing an S-curve laser power which is distributed along the laser oscillating path (sine wave) to improve the microstructure and mechanical properties of the joints. By applying the S-curve and an equal power condition to the 5A06 aluminum alloy, bottom butt sinusoidal path laser oscillating welding was performed. The welding appearance, microstructure and mechanical properties of the welded joints under two laser oscillating welding processes were investigated. Our results showed that laser oscillating welding using the S-curve power allows to obtain good joints when compared to the joints produced with constant power. When the linearly varying laser power of “high-low-high” applied periodically was employed, the grains in the joint structure showed the cyclic “growth-inhibition-growth” phenomenon. This growth mechanism not only refined the grain structure, but also narrowed the columnar region, and improved the mechanical properties of the joint. Compared with the laser oscillating process with constant power, the tensile strength of the joints using the S-curve power was increased by 35.3 %. Moreover, the tensile strength of the welded test coupons with S-curve power was 337 MPa, which is about 99.1% of the base metal (340 MPa). The welded joints using the S-curve power showed larger and deeper dimples, highlighting higher ductility and good plasticity. This paper provides a new approach for the research of laser oscillating welding and the control of laser power to improve the mechanical properties of welded joints.
TL;DR: In this paper , the dissipative noise-like soliton pulses are discovered after additional anomalous dispersion fiber, further demonstrating that the physical laws and optical properties of dissipative solitons are completely different from those of traditional optical pulses.
Abstract: Dissipative solitons are generalized solitons with much larger pulse energy and width than conventional solitons, and the pulse characteristics will be changed dramatically during transmission. Nonlinear photonic absorption device in nonlinear optical resonator can provide saturable absorption effect to generate ultrashort pulses. However, most of the nonlinear photonics devices are based on inorganic materials such as two-dimensional materials with complex production process, and there are relatively few such researches on organics. In this paper, nonlinear photonics absorption device based on hydrazone organics with high molecular polarizability and significant third-order optical nonlinearity generate ultrashort pulses. The dissipative soliton pulses are obtained by controlling the dispersion, and the pulses are compressed to the near-transformation limit of 408 fs with a compression ratio of 44.6. More importantly, the extra-cavity transport properties of dissipative solitons are discussed. Dissipative noise-like soliton pulses are discovered after additional anomalous dispersion fiber, further demonstrating that the physical laws and optical properties of dissipative solitons are completely different from those of traditional optical pulses. We expect that these experimental advances can provide some experimental basis and support for the propagation of dissipative solitons.
TL;DR: In this article, the optical thermometry based on frequency upconversion and the infrared luminescence of Er3+-Yb3+ codoped TeO2-B2O3 (TBO) glasses were reported via melt-quenching technique.
Abstract: This work mainly reports the optical thermometry based on frequency upconversion and the infrared luminescence of Er3+-Yb3+ codoped TeO2-B2O3 (TBO) glasses prepared via melt-quenching technique. The amorphous nature of the prepared glass samples has been confirmed from the XRD analysis. FTIR analysis of the prepared glasses shows the existence of possible bands along with the phonon energy ∼670 cm−1. Judd-Ofelt analysis has been performed on the basis of absorption spectra and various radiative parameters calculated. The order of the intensity parameters (Ω6 > Ω2 > Ω4) indicates ionic nature of the Er-O bond which is further confirmed by the naphelauxetic ratio, covalency and bonding parameter. The enhancement of about 155 times and 327 times in the green and red UC emission intensity of the codoped glass as compared to the Er3+ doped TBO glass has been reported. The absorption cross-section around 980 nm in the codoped glass is found to be ∼43 times larger as compared to the 4I15/2 → 4I11/2 absorption transition in the Er3+ doped glass. The temperature sensing study of the codoped glass with high ‘Ω6’ value has been performed and low value of the absolute sensitivity has been explained on the basis of Judd-Ofelt parameters. The figure of merit for gain bandwidth (9216.81 × 10−27 cm3) & maximum gain coefficient (2.27 cm−1) corresponding to the infrared luminescence peaking at ∼1.5 μm and spectroscopic quality factor (0.28) have been evaluated.
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.
TL;DR: In this paper, the microstructural aspects and mechanical properties of laser beam welded ASTM A335 Grade P91 and P22 steel joint for power plant applications were investigated, and detailed microstructure characterization of the weld metal and heat-affected zone (HAZ) were carried out in as-welded and postweld heat treatment (PWHT) conditions.
Abstract: The present manuscript investigates the microstructural aspects and mechanical properties of laser beam welded ASTM A335 Grade P91 and P22 steel joint for power plant applications. Detailed microstructure characterization of the weld metal (WM) and heat-affected zone (HAZ) were carried out in as-welded and post-weld heat treatment (PWHT) conditions. A variation in microstructure was observed along the welded joint. This resulted in inhomogeneity in mechanical properties. The PWHT resulted in the formation of the stabilized microstructure in weldments and reduced heterogeneity in mechanical properties along the weldments. Tensile strength of weld joint in as-welded (AW) and PWHT condition was found slightly higher (617 MPa and 628 MPa, respectively) than the tensile strength of P22 steel (610 MPa). The fracture location for both AW and PWHT was observed in the P22 base region, which indicates that welded joint is stronger than the base material. Maximum tensile strength of the WZ was found 864 MPa in the as-welded condition. The hardness of WM, P91 CGHAZ and P22 CGHAZ were found 376 HV, 420 HV and 302 HV, respectively. After the PWHT, the hardness of the WM, P91 CGHAZ, P91 ICHAZ, P22 CGHAZ and P22 ICHAZ were measured 237 HV, 264 HV, 212 HV, 208 HV and 190 HV, respectively. The reduction in hardness is attributed to the tempering reaction, which results in the formation of the tempered martensite in WM and HAZ of P91 and tempered bainite in P22 HAZ. The impact toughness of the weld metal in as-welded condition was measured 85 J, which was lower than P22 and P91 steel. PWHT resulted in a drastic increase in impact toughness of WM and it was 145 J. The impact toughness of the P22 and P91 HAZ was measured 146 J and 92 J, respectively, for AW and 168 J and 140 J, respectively, after PWHT. The optimum microstructure and mechanical properties of the dissimilar welded joint were obtained after the PWHT.
TL;DR: In this paper , the authors reported the synthesis of TiO 2 nanowires (NWs) decorated with Au nanoparticles (NPs) by pulsed laser ablation technique for anticancer applications.
Abstract: • Anticancer activity of Tio2/Gold nanocomposite prepared by laser ablation technique. • Cytotoxicity in breast and cervical cancers. • Cervical (HELA) and breast (MCF7) cancer cell lines using MTT (3-(4, 5-Dimethylthiazol-2-yl)-2, 5-Diphenyltetrazolium Bromide) method. • TiO 2 -Au nanocomposite could potentially used to inhibit the growth of cancerous cells. This work reports the synthesis of TiO 2 nanowires (NWs) decorated with Au nanoparticles (NPs) by pulsed laser ablation technique for anticancer applications. Various analytical techniques were employed to characterize the fabricated samples including field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectrometry (EDX), UV–Vis spectrophotometry, Raman spectroscopy, and photoluminescence (PL). The FESEM images confirm the anchoring of Au NPs on the surfaces of the TiO 2 NWs. The anticancer activity of pristine TiO 2 NWs, Au NPs, and TiO 2 -Au nanocomposite were evaluated on cervical (HELA) and breast (MCF7) cancer cell lines using MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) method. The results show that the decoration of TiO 2 NWS with Au NPs significantly enhanced the anticancer activities against MCF7 and HELA cancer cells with an improvement of 43% and 41 %, respectively. Thus, TiO 2 -Au nanocomposite prepared using pulsed laser ablation could potentially be used to inhibit the growth of cancerous cells.
TL;DR: In this paper , the optical parameters were calculated in the linear path: the band tail energy and the optical bandgap energy determined in this work by several methods, including the first derivative of the transmittance, reflectance, and optical absorption coefficient curves as a function of wavelength, as well as the second derivative of Transmittance curves.
Abstract: At room temperature, the Cd30Se50S20 ternary thin films with thicknesses ranging from 100 to 400 nm were synthesized using a vacuum evaporation process in an adequate atmosphere of pure nitrogen. X-ray and scanning electron microscopy techniques were used to validate the amorphous nature of the investigated thin films. Changing the thickness of the pristine thin film had a significant effect on controlling the linear and nonlinear optical properties. The optical absorption coefficient was determined using the optical measurements (the transmittance, the reflectance spectra and the film’s thickness) in the range of (300–2500 nm) and the thickness of the thin layer. The optical parameters were calculated in the linear path: the band tail energy and the optical bandgap energy determined in this work by several methods, including the first derivative of the transmittance, reflectance, and optical absorption coefficient curves as a function of wavelength, as well as the second derivative of the transmittance curves. The optical bandgap energy was also computed as a function of photon energy using Tauc formula, the relaxation time, and the portions of the optical conductivity curves. It turns out that the bandgap energy and the tail energy were affected by the increase in thickness so that the first decreases and the other increases in a harmonious behavior. The linear optical constants (the extinction coefficient, the refractive index), the linear dispersion parameters (the single oscillator energy, the dispersion energy), and the linear dielectric parameters were all affected by the increase in thickness of the thin layer. The phase velocity, the group velocity, and Kirchhoff functions were determined, as well as the linear optical dispersion coefficient. The Boling formula, on the other hand, was used to compute the nonlinear refractive index. Finally, the spectral distribution of molar parameters was discussed.
TL;DR: In this paper , the microstructural aspects and mechanical properties of laser beam welded ASTM A335 grade P91 and P22 steel joint for power plant applications were investigated, and detailed microstructure characterization of the weld metal and heat-affected zone (HAZ) were carried out in as-welded and postweld heat treatment (PWHT) conditions.
Abstract: The present manuscript investigates the microstructural aspects and mechanical properties of laser beam welded ASTM A335 Grade P91 and P22 steel joint for power plant applications. Detailed microstructure characterization of the weld metal (WM) and heat-affected zone (HAZ) were carried out in as-welded and post-weld heat treatment (PWHT) conditions. A variation in microstructure was observed along the welded joint. This resulted in inhomogeneity in mechanical properties. The PWHT resulted in the formation of the stabilized microstructure in weldments and reduced heterogeneity in mechanical properties along the weldments. Tensile strength of weld joint in as-welded (AW) and PWHT condition was found slightly higher (617 MPa and 628 MPa, respectively) than the tensile strength of P22 steel (610 MPa). The fracture location for both AW and PWHT was observed in the P22 base region, which indicates that welded joint is stronger than the base material. Maximum tensile strength of the WZ was found 864 MPa in the as-welded condition. The hardness of WM, P91 CGHAZ and P22 CGHAZ were found 376 HV, 420 HV and 302 HV, respectively. After the PWHT, the hardness of the WM, P91 CGHAZ, P91 ICHAZ, P22 CGHAZ and P22 ICHAZ were measured 237 HV, 264 HV, 212 HV, 208 HV and 190 HV, respectively. The reduction in hardness is attributed to the tempering reaction, which results in the formation of the tempered martensite in WM and HAZ of P91 and tempered bainite in P22 HAZ. The impact toughness of the weld metal in as-welded condition was measured 85 J, which was lower than P22 and P91 steel. PWHT resulted in a drastic increase in impact toughness of WM and it was 145 J. The impact toughness of the P22 and P91 HAZ was measured 146 J and 92 J, respectively, for AW and 168 J and 140 J, respectively, after PWHT. The optimum microstructure and mechanical properties of the dissimilar welded joint were obtained after the PWHT.
TL;DR: In this paper, a single-mode eccentric-core D-shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor is proposed and comprehensively investigated based on Finite Element Method (FEM).
Abstract: A single-mode eccentric-core D-shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor is proposed and comprehensively investigated based on Finite Element Method (FEM). The critical properties of the sensor such as single mode regimes, beam spot size, and confinement losses are all tailored for more practical network-integrable PCF SPR sensor with high coupling efficiency using commonly used single-mode optical fibers. The sensor has analyte Refractive-Index (RI) detection range between 1.330 and 1.420 with maximum sensitivity of 21200 nm/Refractive-Index-Unit (RIU), maximum Figure-of-Merit (FOM) of 294 RIU−1, maximum resolution of 4.72 × 10-6 RIU for analyte refractive index change of 0.005 with the finest Full-Width at Half-Maximum (FWHM) of 29 nm, and a maximum confinement loss of 14 dB/cm. The sensor exhibits high linear response at low analyte RI regime between analyte index 1.330 and 1.370. The proposed sensor design can be fabricated using comparatively simpler stack-and-draw method which is based solely on standard circular glass capillaries and solid rods.
TL;DR: In this article , the optical thermometry based on frequency upconversion and the infrared luminescence of Er3+-Yb3+ codoped TeO2-B2O3 (TBO) glasses were reported via melt-quenching technique.
Abstract: This work mainly reports the optical thermometry based on frequency upconversion and the infrared luminescence of Er3+-Yb3+ codoped TeO2-B2O3 (TBO) glasses prepared via melt-quenching technique. The amorphous nature of the prepared glass samples has been confirmed from the XRD analysis. FTIR analysis of the prepared glasses shows the existence of possible bands along with the phonon energy ∼670 cm−1. Judd-Ofelt analysis has been performed on the basis of absorption spectra and various radiative parameters calculated. The order of the intensity parameters (Ω6 > Ω2 > Ω4) indicates ionic nature of the Er-O bond which is further confirmed by the naphelauxetic ratio, covalency and bonding parameter. The enhancement of about 155 times and 327 times in the green and red UC emission intensity of the codoped glass as compared to the Er3+ doped TBO glass has been reported. The absorption cross-section around 980 nm in the codoped glass is found to be ∼43 times larger as compared to the 4I15/2 → 4I11/2 absorption transition in the Er3+ doped glass. The temperature sensing study of the codoped glass with high ‘Ω6’ value has been performed and low value of the absolute sensitivity has been explained on the basis of Judd-Ofelt parameters. The figure of merit for gain bandwidth (9216.81 × 10−27 cm3) & maximum gain coefficient (2.27 cm−1) corresponding to the infrared luminescence peaking at ∼1.5 μm and spectroscopic quality factor (0.28) have been evaluated.
TL;DR: In this paper, a Fe-based laser cladding coatings with different-sized WC particles were fabricated on the surface of 16Mn steel, aiming at exploring the effect of different-size WC addition on microstructure evolutions, microhardness and wear resistance of composite coatings.
Abstract: In the present study, Fe-based laser cladding coatings with different-sized WC particles were fabricated on the surface of 16Mn steel, aiming at exploring the effect of different-sized WC addition on microstructure evolutions, microhardness and wear resistance of composite coatings. Results showed that for composite coatings, a change in particle size of WC had a negligible effect on phase constituents, but it was found effective in influencing the microstructure, microhardness, and wear resistance. The main phases of composite coatings were mainly composed of α-Fe, γ-(Fe, Ni), WC and M23C6 (M: Cr, W, Fe). Small-sized WC played a positive effect in forming homogeneous and finer microstructure in composite coating, while the effect of large-sized WC was the opposite. The microstructure of small-sized WC-contained coating only contained dendritic α-Fe matrix and inter-dendritic composite carbides of WC + M23C6. The microstructure of large-sized WC-contained coating in the centre and edges was entirely different. The microstructure in the centre consisted of dendritic α-Fe matrix and inter-dendritic fine lamellar eutectics of α-Fe + M23C6. The microstructure in the edges consisted of dendritic α-Fe matrix and inter-dendritic carbides of M23C6. Besides, the strengthening effect of small-sized WC was much better than that of large-sized WC.
TL;DR: This paper summarizes the work performed on metals, non-metals and ceramics in the area of the LHMMP to create 3D micro features and future development efforts needed in this area of laser-based hybrid machining are suggested to multiply the process utility.
Abstract: Laser beam micromachining is a prominent method for micromachining applications. But it has some drawbacks like thermal stresses, uncontrolled dimensions, burrs, and spatter. Similarly, non-conventional processes like ECM, EDM, and conventional machining processes, namely turning, drilling and milling, also have limitations due to slow process and tooling costs. Researchers are continuously seeking hybrid machining, like laser-based hybrid machining methods, to improve the product's quality characteristics. Researchers have thoroughly investigated the laser-based hybrid process mechanism in the last decade and have identified different issues and control strategies to improve its performance. This paper reviews laser-based hybrid micromachining processes (LHMMP) in which LBM is combined with conventional processes and non-conventional processes in an assisted or sequential manner. Also, other energy sources assisting the laser beam machining process, viz. vibration, magnetic field, electric field, fluids, and gases, are reviewed in the current work. This paper summarizes the work performed on metals, non-metals and ceramics in the area of the LHMMP to create 3D micro features. Theoretical and experimental studies, mechanisms of machining, machining setups, and the impact of process parameters on laser-based hybrid micromachining techniques are reviewed in detail. The hybrid processes elevate the process efficiency, surface quality, tooling cost and precision of fabricated parts. In the last section of this paper, future development efforts needed in this area of laser-based hybrid machining are suggested to multiply the process utility.
TL;DR: In this article , a nanosecond pulsed laser was used to clean polyurethane paint on Al-Mg series aluminum alloy substrate by using a nano-laser.
Abstract: This paper presents laser cleaning of blue polyurethane paint on Al-Mg series aluminum alloy substrate by using a nanosecond pulsed laser. Experiments were conducted at the laser fluence of 1.2–8.0 J/cm2. The specimen topography and surface chemical composition were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), respectively. The paint could be completely removed without damaging the substrate at the laser fluence of 3.2 J/cm2. Ablation, spallation and vaporization are the main cleaning mechanisms during laser cleaning of the paint. The surface roughness was significantly decreased at higher laser fluence due to surface melting. With the increasing of laser fluence, the scratched grooves on the sample surface turned shallow and three different surface topographies were formed at the laser fluence of 4.8 J/cm2, 6.4 J/cm2 and 8.0 J/cm2. The formation mechanisms of the three surface topographies are discussed, which provides a reference for the purpose of polishing the substrate surface while laser cleaning.