Laser Properties Research Articles

Effect of Feature Size on Defects, Microstructure, and Mechanical Properties of Selective Laser Melted AlSi10Mg Lattice Structure

Selective laser melting lightweight lattice structures have broad application prospects in the aerospace field. Understanding the dependence of mechanical performance on feature size is crucial for structure design. This work optimized the process parameters based on large-size metal blocks (20 mm) and then fabricated submillimeter features with a size of 0.4~1.0 mm. The influence of feature size on the defects, microstructures, and mechanical properties was investigated. The results showed that the dimensional errors for all size features were above 15%. When matched with appropriate border offset, these features could be printed precisely. The densification of submillimeter features was more than 99%, demonstrating the applicability of the optimized process parameters for the fine features. The porosity and relative roughness decreased and tended to stabilize with increasing feature size. Due to having less defects, the thicker features exhibited better mechanical properties in terms of ultimate strength and elongation. After being processed with polishing treatment, the roughness was reduced below 1 μm and the tensile strength increased above 320 MPa. The elastic modulus, yield strength, and elongation were also significantly improved.

Effects of rapid infrared radiation heating on the warping deformation and mechanical properties of selective laser melted Co-Cr dental alloy.

Infrared radiation heating (IRH) technology has been innovatively applied to the annealing of selective laser melted (SLM) cobalt chromium (Co-Cr) frameworks. However, previous studies have not reported the effects of IRH on the warping deformation and mechanical properties of these frameworks. The purpose of this in vitro study was to investigate the effects of IRH on the warping deformation and mechanical properties of dental SLM Co-Cr alloy and to evaluate its potential applications in dental restorations. Two types of specimens, bone-shaped tensile specimens and warping deformation specimens (cantilever beam structures), were fabricated by SLM, followed by annealing using IRH and general furnace heating (GFH). The specimens were divided into 4 groups (n=6) based on the applied heat treatment method and build direction (IRH-XY; IRH-Z; GFH-XY; GFH-Z). The cantilever beam support structure of the warping deformation specimen was cut using wire cutting, and the warping deformation was measured using a digital image correlation optical extensometer. Tensile tests were used to evaluate mechanical properties, with the fracture characteristics being observed using a scanning electron microscope (SEM). A micro-Vickers hardness tester was used to measure the microhardness. The microstructures were analyzed using a metallographic microscope. All data were analyzed using a 1-way ANOVA and the Tukey Honestly Significant Difference test (α=.05). The surfaces of the SLM Co-Cr warping deformation specimens treated with IRH showed slight oxidation, while those treated with GFH exhibited a dark black appearance. No significant difference was found in deformation between the IRH group (0.412 ±0.039 mm) and the GFH group (0.379 ±0.070 mm) (P>.05). The elongation of the longitudinally built specimens was significantly higher than that of their transversely built counterparts (P<.05), while the yield strength showed an opposite trend. The longitudinally built specimens demonstrated ductile fracture characteristics, while the transversely built specimens displayed quasi-cleavage fractures. The specimens treated with IRH exhibited comparable tensile strength and microhardness with the GFH-treated specimens, with no statistically significant differences (P>.05). IRH treatment resulted in finer grains in the SLM Co-Cr alloy. Many fine second-phase particles precipitated from the matrix in the longitudinally built specimens, while few were observed in the transversely built specimens. The SLM Co-Cr specimens treated with IRH achieved comparable warping deformation and mechanical properties with those of the GFH-treated specimens. The IRH technology holds great potential for application to dental restorations.

Interface microstructure and mechanical properties of selective laser melting‐formed CuCrZr alloy for 316 L stainless steel

AbstractA bimetallic structure combines the properties of two constituent materials and has a high comprehensive performance. Selective laser melting has been widely studied for its advantages such as high utilization of raw materials, short processing cycles, and the ability to form complex structures. The 316 L‐CuCrZr bimetallic structure was successfully prepared using selective laser melting. Its microstructural analysis and energy spectrum analysis indicated that the 316 L stainless steel and the CuCrZr alloy formed a good interfacial bond and that the elements at the interface exhibited a gradient distribution. The tensile strength of 316 L‐CuCrZr was 280.97 MPa, which was close to the strength of the CuCrZr alloy. The interface hardness showed a decreasing trend from that of the stainless steel to that of the copper alloy, which indicated that the interface between the 316 L stainless steel and the CuCrZr alloy was well bonded.

Mechanical properties of laser welded similar and dissimilar steel joints of TBF1050 and DP1000 steel sheets

Abstract TBF1050 and DP1000 sheets in different thicknesses were laser welded in butt configuration. The welds were performed both similar and dissimilar. Welding speed was changed between 40 and 120 mm/min. Characterization of the welds was carried out by means of microstructure, microhardness, tensile properties and fractography. The grain structure in heat affected zone (HAZ) on DP1000 side was a relatively coarser than that on TBF1050 side. The highest hardness was obtained in fusion zone. The presence of TBF1050 steel in the joint increased the hardness of the fusion zone. On both steel sides, the hardness in a narrow zone between the tempered zone and the base metal decreased below the hardness of the base metals (softening zone). The softening zone hardness on TBF1050 side was relatively higher than that on DP1000 side. The tensile strengths of each laser welded joint, except for DP1000 similar joint, were all higher than 1,000 MPa. When the fractures occurred on the TBF1050 side, the tensile strength was higher. Whether the TBF1050 steel sheet was galvanized or not did not cause any significant effect on the microstructure and the mechanical properties of the joints. The joint fractured from HAZ had a completely brittle fracture behavior.

Quantum and Statistical Properties of a Non-degenerate Three-Level Laser Pumped by Electron Bombardment and Coupled to a Two-Mode Thermal Reservoir

Quantum and Statistical Properties of a Non-degenerate Three-Level Laser Pumped by Electron Bombardment and Coupled to a Two-Mode Thermal Reservoir

Effects of solute supersaturation and re-precipitation on microstructure and mechanical properties of selective laser melted Al−Mn−Mg−Sc−Zr alloys

Effects of solute supersaturation and re-precipitation on microstructure and mechanical properties of selective laser melted Al−Mn−Mg−Sc−Zr alloys

Effect of hot deformation treatment on the microstructure and mechanical properties of selective laser melted AlSi10Mg alloy

Effect of hot deformation treatment on the microstructure and mechanical properties of selective laser melted AlSi10Mg alloy

Influence of Al microalloying on microstructure and mechanical properties of laser directed energy deposited AISI 420 steel

Influence of Al microalloying on microstructure and mechanical properties of laser directed energy deposited AISI 420 steel

Emission dynamics and spectrum of a nanoshell-based plasmonic nanolaser spaser

Abstract We study theoretically the emission and lasing properties of a single nanoshell spaser nanoparticle with an active core and a plasmonic metal shell. Using time-dependent equations for the gain medium and metal, we calculate the lasing threshold through an instability analysis. Below threshold, the nanoshell acts as an optical amplifier when excited by an external probe field, while above threshold, it enters a regime of autonomous lasing. At the gain threshold, the lasing starts at one frequency, typically a plasmon resonance of the nanoparticle. With increasing gain, the emission then broadens to additional frequencies. This result contrasts with previous findings reporting only a single emission wavelength above threshold. We also compute the full spectrum and linewidth of the nanolaser, revealing strong frequency shifts and an asymmetrical lineshape. Finally, we demonstrate that the emission line can be tuned across the visible spectrum by modifying the aspect ratio of the nanoshell.

Improvement in Mechanical and Corrosion Properties of Laser and electron Beam Welded AISI 304 Stainless Steel Joints by Laser Shock Peening

Improvement in Mechanical and Corrosion Properties of Laser and electron Beam Welded AISI 304 Stainless Steel Joints by Laser Shock Peening

Tailoring performance through loss engineering in ring-waveguide lasers for enhanced Single-Mode lasing

Loss engineering is a valuable approach for controlling the properties of ring-waveguide lasers. By carefully adjusting the waveguide’s loss parameters, it is possible to create customized lasers with improved performance for specific applications. In this study, we present the fabrication, characterization, and simulation of a ring-waveguide laser with loss-engineering capabilities. Initially, we optimized the waveguide’s cross-section to reduce scattering loss caused by side-wall roughness, achieving a low loss of 0.03 dB/cm. Next, we investigated the effect of the coupling coefficient on the lasing properties of the device by varying the gap between the waveguide and the resonator. Our experimental results demonstrate that by fine-tuning the coupling coefficient, we can achieve single-mode lasing with an impressive side-mode suppression ratio (SMSR) of over 47 dB at a wavelength of 598 nm. These findings offer valuable insights into loss-engineering techniques for ring-waveguide lasers and showcase the potential for single-mode emission lasers with high stability, which can be applied in various fields.

Single‐Mode Lasing by Selective Mode Structure Breaking

AbstractSingle‐mode lasers are highly desirable for applications in optical communication, quantum information, and photonic computing, but their realization is challenging due to the competition of multiple closely spaced resonant modes in microcavities. This paper proposes a novel approach, termed mode structure breaking, to achieve high‐performance single‐mode lasing in an individual laser cavity. By introducing selective spatial structure defects, the mode structure of competing modes can be broken, enabling single‐mode selection without huge losses. As proof of concept, femtosecond (fs)‐laser ablation is experimentally employed to introduce external angle defects on a microdisk cavity, effectively eliminating mismatched competing modes and thus achieving single‐mode lasing output. The lasing characteristics are further optimized by incorporating a punched hole to suppress remaining high‐order lasing modes. Notably, the fabricated perovskite laser sources, which are called mode‐structure‐breaking lasers, demonstrate excellent single‐mode lasing properties, including stability, an ultralow threshold (≈2.31 µJ cm−2), and a narrow linewidth (≈0.15 nm). Conclusively, this comprehensive study of manipulating lasing mode by breaking mode structure may provide a promising approach to realizing single‐mode lasing in a single structure, which is significant for producing on‐chip laser source arrays for use in photonic integrated circuits.

On the Influence of Microstructure and Properties of Direct Laser Deposited 50Cr6Ni2Y Coatings with Different TiC Contents

Three 50Cr6Ni2Y + x wt.% TiC (x = 1.5, 3.0, 4.5) alloy steel coatings were prepared using direct laser deposition (DLD) technology. The microstructure, microhardness, and wear resistance of DLD samples were studied. The results indicate that DLD coatings were composed of α-Fe (Fe-Cr-Ti), γ-Fe (Fe-Ni), and TiC. When the added TiC content was 3.0 wt.%, the DLD coating without cracks was fabricated, and TiC particles were well embedded in the sample. In addition, the coating demonstrated the best performance, with a microhardness of 758 ± 23.3 HV0.2, an average friction coefficient of 0.58, and a wear rate of 0.37 %. The addition of an appropriate amount of TiC as a reinforcing phase, on the one hand, had played a role in the second phase strengthening. On the other hand, the diffusion interfaces formed between TiC particles and the matrix allowed some Ti elements to melt into the matrix and formed a solid solution, playing a role in solid solution strengthening. The results could provide a reference for the preparation and repair of laser additive manufacturing high-performance wear-resistant parts.

Mid-infrared pulsed fiber laser source at 4.3 µm based on a CO2-filled anti-resonant hollow-core silica fiber

Fiber lasers in the mid-infrared (mid-IR) band are of great interest due to their wide range of applications such as manufacturing, defense, spectroscopy, and free-space communication. Due to the immaturity of the soft glass fiber fabrication technology and the limitation of the type of doped rare earth, laser power scaling and wavelength expansion above 4 µm are greatly limited. Lasers based on gas-filled hollow-core fibers (HCFs) have proved to be an effective way of generating mid-IR lasers. We demonstrate a pulsed 4.3 µm laser source based on a CO2-filled HCF for the first time. The pulse energy characteristics and output spectrum of the mid-IR laser have been investigated. The maximum pulse energy of the mid-IR laser is 236 nJ. The maximum average power of the mid-IR laser is 297.8 mW with a slope efficiency of 17.3%. A step-tunable mid-IR output is achieved from 4293.718 nm to 4392.085 nm including 8 emission lines. Furthermore, the time-domain and frequency-domain properties of the mid-IR laser have been studied to understand laser operation better. This work has an important reference value for the development of pulsed mid-IR fiber gas laser sources.

Linear and nonlinear optical properties of femtosecond laser inscribed waveguides into GLS glass

Gallium lanthanum sulfide (GLS) glass is a promising material for mid-infrared photonics due to its wide transmission window and its high nonlinear refractive index that is almost three orders of magnitude higher than that of fused silica. In this paper, we present the results of a detailed study into the linear and nonlinear optical properties of waveguides fabricated in GLS glass via ultrafast laser direct-inscription using three different techniques: cumulative heating in the thermal regime as well as multi-scan and half-scan in the athermal regime. Using quadriwave lateral shearing interferometry, we fully characterized the refractive index profiles of such inscribed waveguides and found no difference between half-scan and multi-scan writing which indicates the absence of laser-induced stress in this soft glass in stark contrast to fused silica. In terms of nonlinearity, we utilized self-phase modulation (SPM)-induced spectral broadening experiments at mid-IR wavelengths to demonstrate that waveguides fabricated in the athermal regime preserve the high intrinsic nonlinearity of the GLS bulk material, outperforming those written in the thermal regime based. These findings pave the way for the fabrication of fiber-coupled optical waveguide chips for nonlinear mid-infrared photonics.

Effect of Solution Aging Heat Treatment on Tribological Properties of Selective Laser Melted WC/18Ni300 Composite

Different contents of WC particle‐reinforced 18Ni300 composites are prepared by selective laser melting method, and the tribological properties are comparatively studied before and after solution aging heat treatment. The results show that a part of WC particles are dissolved, and no obvious pore defects appear. With the increase of WC content, the microstructure gradually transforms from cellular and fine columnar α‐Fe martensite to γ‐Fe austenite. After solution aging heat treatment, the phase is transformed into acicular martensite. The grain size significantly decreases, and the Vickers hardness increases. The grain size decreases and the hardness increases with increasing WC contents. For the as‐built composite, the friction coefficient first decreases and then increases, and the wear rate first increases and then decreases with the increase of WC content. With WC content increasing, the wear rate first decreases and then increases. After heat treatment, the tribological properties are improved. The groove of the specimens before heat treatment is deep with large delaminated craters, and the wear mechanism is dominated by adhesive and abrasive wear. The grooves become shallower, and the adhesive trace becomes lighter after heat treatment. The wear mechanism is mainly adhesive wear and abrasive wear, accompanying with oxidative wear.

High peak power passive Q-switched widely tunable Tm:YAP laser

This paper presents a novel, widely tunable, passively Q-switched Tm:YAP laser operating at high peak power in the 2-micron spectral range. While widely tunable lasers typically operate in continuous wave (CW) mode, and customary high peak power designs rely on active Q-switching methods, our innovative design combines both features in an all-passive configuration. The continuous tunability spectrum spans 41 nm, from 1911 nm to 1952 nm. Wavelength tunability was achieved using a 25μm thick YAG etalon. A Cr:ZnS saturable absorber is used for passive Q-switching, achieving a maximal repetition rate of 3 kHz, maximal energy per pulse of 1.42 mJ, and a very high maximum peak power of 54 kW. Additionally, a detailed theoretical analysis of the energy dependency on the wavelength is discussed. Such laser properties, especially implemented in an all-passive configuration, have great application prospects in many fields.

Localized Laser Heat Treatment on AISI 1045 Steel Using a LPBF Laser

ABSTRACTLaser heat treatment (LHT) can provide local microstructure modification for metallic materials. This study investigates the viability of LHT on AISI 1045 steel using a laser designed for laser powder bed processing (LPBF) with a very small beam diameter compared to existing literature. Energy density models from the literature are analyzed and adapted to improve consistency across varying laser properties, mainly focusing on spot size and laser–material interaction time. Fifteen different laser parameter schematics are evaluated, comparing hardness versus depth relations as well as laser‐affected zone (LAZ) profiles. Through adapting the energy density model, new laser parameters are calculated and demonstrated to produce a valid localized heat treatment.

Microstructure and mechanical properties of aluminum alloy laser welded joint assisted by alternating magnetic field

Magnetic field-assisted laser welding is an effective method to improve the quality of laser-welded joints. In this study, laser welding was conducted on a 2 mm thick sheet of 6061-T6 aluminum alloy, with the assistance of an alternating magnetic field oriented perpendicular to the surface of the sheet. The effects of the alternating magnetic field on the macrostructure, molten pool flow, porosity, grain morphology, and microhardness of the weld seam were analyzed. The results indicate that applying the alternating magnetic field results in more uniform and finer fish scale patterns on the upper surface of the weld. The porosity of the weld is significantly reduced. The Lorentz force generated by the alternating magnetic field suppresses liquid metal flow from the center to the edges of the molten pool, thereby hindering the heat flow and transfer within the pool. This concentration of heat in the lower part of the molten pool increases the size of equiaxed grains at the weld center and promotes the formation of more branches in the columnar grains near the fusion line. Some columnar grains in the columnar grain zone transform into equiaxed grains. Moreover, the microhardness distribution of the weld becomes more uniform, and the hardness in the heat-affected zone increases. Tensile tests revealed that all samples fractured within the weld seam, with the tensile strength of the welded joints increasing by 12.7%. The fracture mode transitions from a mixed ductile-brittle fracture to a purely ductile fracture.

Influence of crystal field inhomogeneities on the spontaneous and laser tuning emission of a Nd3+-doped Li2O-BaO-Al2O3-P2O5 glass

The present work focuses on the spectroscopic and laser properties of Nd3+ in a Li2O-BaO-Al2O3-P2O5 aluminophosphate glass which includes Judd-Ofelt calculation, stimulated emission cross-section of the 4F3/2→4I11/2 emission laser transition, lifetime of the 4F3/2 state and quantum efficiency. Site-selective laser spectroscopy and stimulated emission under selective excitation has been performed to determine the crystal field inhomogeneity at the Nd3+ site together with its broadening effect on the spontaneous and laser emissions. However, a much narrowed laser emission has been achieved by using an intracavity tilting plate which acts as a tunable optical filter to adjust the laser wavelength.