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In this paper, we proposed a technique, ultrafast laser machining–picosecond laser welding, to fabricate an embedded thin film by placing a coating material (ZnO powders) between the interface of two glass substrates. We researched the thickness (embedding depth of ZnO powders) and the formation mechanism of the embedded thin film and the zinc content and distribution. Under our experimental conditions, an embedded thin film of 600 μm thickness was formed. At a distance of 340 μm within the embedded thin film, the zinc content peaked at 400 cps. Finally, we fabricate an embedded thin film with the bonding strength of 12.22 MPa. This technique breaks through the bottlenecks of thin films fabricated by conventional lasers, such as long duration, low precision and serious chemical pollution, which has great significance for achieving high-end manufacturing of thin-film devices. [ABSTRACT FROM AUTHOR]

Soda–lime glass has a wide range of applications in the fields of smart electronics, optical components, and precision originals. In order to investigate the effect of processing parameters on picosecond Bessel laser cutting of soda–lime glass and to achieve high-quality soda–lime glass cutting, a series of cutting experiments were conducted in this study. In this study, it was found that the machining point spacing, the incident laser energy, and the number of burst modes had a significant effect on the machining of the samples. The atomic force microscope (AFM) showed a better quality of roughness of the machined cross-section when the spacing of the machining points was 1 μm, a locally optimal solution was obtained when the number of burst modes was 2, and a locally optimal solution was also obtained when the incident laser power was 11.5 W. In this study, better machining quality was achieved for soda–lime glass of 1 mm thickness, with an average roughness of 158 nm and a local optimum of 141 nm.

Utilizing the principle of laser-induced periodic surface structures (LIPSSs), this research delves into the morphological evolution of single-crystal silicon surfaces irradiated by a near-infrared picosecond laser through a scanning mode. With the increase in laser energy density, the nanostructure morphology on single-crystal silicon surfaces induced by incident lasers with different polarization directions sequentially produces high spatial-frequency LIPSSs (HSFLs) with a period of 220 nm ± 10 nm parallel to the laser polarization, low spatial-frequency LIPSSs (LSFLs) with a period of 770 nm ± 85 nm perpendicular to the direction of the polarization, and groove structures. Furthermore, by varying the angle between the laser polarization and the scanning direction, the study examined the combined anisotropic effects of the laser polarization scanning direction angle and the laser polarization crystal orientation angle on the genesis of LIPSSs on single-crystal silicon (100) surfaces. The experiments revealed polarization-related anisotropic characteristics in the morphology of HSFLs. It was found that when the polarization angle approached 45°, the regularity of the LSFLs deteriorated, the modification width decreased, and the periodicity increased. This is critical for the precise control of the LSFLs’ morphology.

This paper presents a study and comparison of surface effects induced by picosecond and nanosecond laser modification of a Ti6Al4V alloy surface under different ambient conditions: air and argon- and nitrogen-rich atmospheres. Detailed surface characterization was performed for all experimental conditions. Damage threshold fluences for picosecond and nanosecond laser irradiation in all three ambient conditions were determined. The observed surface features were a resolidified pool of molten material, craters, hydrodynamic effects and parallel periodic surface structures. Laser-induced periodic surface structures are formed by multi-mode-beam nanosecond laser action and picosecond laser action. Crown-like structures at crater rims are specific features for picosecond Nd:YAG laser action in argon-rich ambient conditions. Elemental analysis of the surfaces indicated nitride compound formation only in the nitrogen-rich ambient conditions. The constituents of the formed plasma were also investigated. Exploring the impact of process control parameters on output responses has been undertaken within the context of laser modification under different environmental conditions. Parametric optimization of the nanosecond laser modification was carried out by implementing an advanced method based on Taguchi’s parametric design and multivariate statistical techniques, and optimal settings are proposed for each atmosphere.

Fused silica is widely used as a material for optical lenses owing to its excellent optical properties and low thermal expansion coefficient. However, as a hard and brittle material, there is very limited option of processing technologies to machining fused silica with surface structures. In this paper, a picosecond laser based single crystal diamond tool fabrication technology is proposed to generate micro milling tools with different geometrical designs, and the tool cutting performance is experimentally tested through micro-milling of fused silica under different cutting conditions. An optimal picosecond laser processing path is proposed to inhibit the graphitization of diamond tool and improve the concentricity of tool blades, and a multi-edge milling tool with a minimum rotary diameter of 0.4 mm can be obtained. The effects of rake angle on cutting force and the degree of brittle damage on the subsurface of fused silica are studied by micro milling tests of fused silica using the laser-shaped tools. The results show that the fused silica machined by diamond milling tool with a rake angle of −30° has the best surface finish (Ra = 41.2 nm). Using this laser-machined milling tool, a plurality of micro Fresnel lenses with aperture of 1.6 mm were successfully machined on a fused silica sheet.

BackgroundPicosecond lasers are widely used in dermatologic and cosmetic practice. In clinical practice, informed consent for laser treatments is critical to ensure patients’ understanding of health information.ObjectivesTo evaluate whether video-based informed consent improves patient comprehension and satisfaction.MethodsThe study was performed from August 1 to November 30, 2022. Solar lentigines patients who fulfilled the inclusion criteria were included. Before October 1, 2022, traditional informed consent methods were performed. In the subsequent 2 months, a video-based informed consent was used as an adjunct to traditional consenting methods. Finally, patient comprehension of relevant knowledge about laser treatment and client satisfaction were assessed.ResultsA total of 106 patients were included. The mean number of correct answers in the comprehension assessment in the video-based informed consent group was significantly higher than that in the traditional informed consent group (4.4 ± 1.2 vs. 3.4 ± 1.1, p < 0.001). Compared to the traditional informed consent group, more correct answers in the video-based informed consent group were provided by older patients (3.9 ± 1.2 vs. 2.9 ± 1.1, p = 0.004) and patients with lower education levels (4.1 ± 1.1 vs. 3.0 ± 1.2, p < 0.001). The mean satisfaction score in the video-based informed consent group was significantly higher than that in the traditional informed consent (27.8 ± 5.7 vs. 24.3 ± 6.2, p = 0.003).ConclusionVideo-based informed consent helps patients learn clinical literacy more effectively and improves patient satisfaction, especially in those with lower education levels and older ages.

BackgroundIncreasing numbers of studies demonstrated that picosecond lasers (Picos) were effective and safe for melasma. However, A limited number of randomized controlled trials (RCTs) regarding Picos contribute to a modest level of evidence. Topical hydroquinone (HQ) remains to be the first-line therapy.ObjectiveTo compare the efficacy and safety of non-fractional picosecond Nd:YAG laser (PSNYL), non-fractional picosecond alexandrite laser (PSAL), and 2% HQ cream in the treatment of melasma.MethodSixty melasma patients with Fitzpatrick skin types (FST) III-IV were randomly assigned to the PSNY, PSAL, and HQ groups at a 1:1:1 ratio. Patients in PSNYL and PSAL groups received 3 laser sessions at 4-week intervals. The 2% HQ cream was applied twice daily for 12 weeks in patients of the HQ group. The primary outcome, the melasma area and severity index (MASI) score, was evaluated at weeks 0, 4, 8, 12, 16, 20, and 24. The patient assessment score by quartile rating scale was rated at weeks 12, 16, 20, and 24.ResultsFifty-nine (98.3%) subjects were included in the analysis. Each group showed significant change from baseline in MASI scores from week 4 to week 24. The MASI score in the PSNYL group showed the greatest reduction compared to the PSAL group (p = 0.016) and HQ group (p = 0.018). The PSAL group demonstrated comparable MASI improvement as the HQ group (p = 0.998). The PSNYL group had the highest patient assessment score, followed by the PSAL group and then the HQ group, although only the differences between PSNYL and HQ groups at weeks 12 and 16 were significant. Four patients (6.8%) experienced recurrence. Other unanticipated events were transient and subsided after 1 week to 6 months.ConclusionThe efficacy of non-fractional PSNYL was superior to that of non-fractional PSAL, which was not inferior to 2% HQ, thus non-fractional Picos providing an alternative for melasma patients with FSTs III-IV. The safety profiles of PSNYL, PSAL, and 2% HQ cream were similar.Clinical Trial Registrationhttps://www.chictr.org.cn/showprojen.aspx?proj=130994, ChiCTR2100050089.

In this experimental study, picosecond laser treatment was performed on a nickel-based superalloy Nimonic 263, aiming to investigate the surface effects induced by irradiation in different atmospheric conditions and, concerning changes in surface composition, regarding the possibility for improvement of its functionality. Besides the varying laser parameters, such as a number of pulses and pulse energy, environmental conditions are also varied. All surface modifications were carried out in standard laboratory conditions and a nitrogen- and argon-rich atmosphere. The resulting topography effects depend on the specific laser treatment and could be categorized as increased roughness, crater formation, and formation of the laser-induced periodic surface structures (LIPSS). Changes in the chemical surface composition are distinguished as the potential formation of the protective oxides/nitrides on the sample surface. Numerous characterization techniques analyse the resulting effects on the topography and surface parameters. The multi-response parametric optimization of the picosecond laser process was performed using an advanced statistical method based on Taguchi's robust parameter design. Finally, the optimal parameter conditions for Nimonic 263 modification are suggested. [ABSTRACT FROM AUTHOR]

Multiple laser modalities have been used for melasma treatment. However, the effectiveness of picosecond laser in treating melasma remains unclear. This meta-analysis investigated the effectiveness and safety of picosecond laser for melasma treatment. Randomized controlled trials (RCTs) comparing picosecond laser with conventional treatment for melasma were searched through five databases. The melasma area severity index (MASI)/modified MASI (mMASI) was used to quantify the degree of melasma improvement. Standardized mean differences and 95% confidence intervals were calculated using Review Manager for result standardization. Six RCTs, which used picosecond laser at 1064, 755, 595, and 532 nm wavelengths, were included herein. Picosecond laser significantly reduced the MASI/mMASI, but the results were highly heterogeneous (P = 0.008, I2 = 70%). In the subgroup analysis of 1064 and 755 nm picosecond lasers, 1064 nm picosecond laser significantly reduced the MASI/mMASI with no significant side effects (P = 0.04). Meanwhile, 755 nm picosecond laser did not significantly improve the MASI/mMASI compared with topical hypopigmentation agents (P = 0.08) and caused post-inflammatory hyperpigmentation. Other laser wavelengths could not be used in the subgroup analysis owing to an insufficient sample size. Picosecond laser at 1064 nm is safe and effective for melasma treatment. Picosecond laser at 755 nm is not superior to topical hypopigmentation agents in treating melasma. The exact efficacy of other wavelengths of picosecond laser for melasma treatment remains to be verified in large-scale RCTs. [ABSTRACT FROM AUTHOR]

Picosecond lasers have a very short pulse duration and a high peak power density. When fractional optical delivery systems are attached to picosecond lasers, they generate an array of concentrated microspots with a high fluence surrounded by areas with a low fluence. This article discusses the histologic characteristics and clinical applications of fractional picosecond laser treatment. Fractional picosecond laser produces laser-induced optical breakdown (LIOB) and laser-induced cavitation (LIC) in the epidermis and dermis respectively, and can encourage skin regeneration and dermal remodeling. It has been shown that fractional picosecond laser has a positive effect on facial photoaging, enlarged facial pores, dyspigmentation, wrinkles, and atrophic scars. Further research is still needed to confirm the benefits of fractional picosecond lasers. [ABSTRACT FROM AUTHOR]

Since the introduction of selective photothermolysis, Q-switched nanosecond lasers have been used for the treatment of dermal pigmented lesions. Over the past several years, picosecond lasers have been introduced to the cosmetic community. We recently performed a study comparing a 550 picosecond 755 nm laser versus a 50 ns 755 nm laser, with the purpose of evaluating the clinical efficacy and complications of each laser when treating nevus of Ota. Ten Asian patients with nevus of Ota were enrolled in the study. Each lesion was split into 2 parts, and patients were treated with a 755 nm picosecond laser (PSL) and a 755 nm nanosecond laser (NSL). The clinical endpoint for fluence choice was immediate whitening (PSL: 2.33 ~ 3.36 J/cm2, NSL: 5.5 ~ 7 J/cm2) of the treated area. The pulse duration was fixed at 550 picoseconds (PSL) and 50 ns (NSL). The spot size of each laser was 2.5–3 mm. Laser treatments were performed until excellent clinical improvement was observed. Patients were examined 1 week after the first treatment, at each follow-up visit, and 6 months after the last laser treatment. The average number of treatment sessions to achieve excellent clinical improvement was 4.2 treatments using PSL and 5.4 treatments using NSL. One case of hyperpigmentation and one case of hypopigmentation were observed in the NSL treatment group. There were no complications in the PSL treatment group. The 755 nm 550 picosecond laser is significantly more effective than the 755 nm 50 ns laser in the treatment of nevus of Ota. The PSL treatment group also had minimum side effects. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the efficacy and safety of fractional 1064 nm picosecond Nd:YAG laser (FPNYL) in the treatment of post‐acne erythema (PAE) of adult Chinese. Materials and methods: A total of 22 patients received 1 session of treatment and were followed up at the eighth week. Primary outcomes were measured by the Clinician erythema assessment scale (CEAS). Secondary outcomes included a global aesthetic improvement scale (GAIS) and patients' assessment of satisfaction on a five‐point scale. Pain scores and adverse effects were also evaluated. Results: Twenty‐two patients with Fitzpatrick skin types III and IV were enrolled in the study and completed all treatments and follow‐up visits. The mean CEAS scores fell from 2.74 ± 0.80 to 1.95 ± 0.75 (p < 0.05). The mean GAIS of PAE improvement was 2.46 ± 0.68. Erythema percentile scores by VISIA increased from 32.63 ± 7.0 to 45.75 ± 11.45 (t = 5.442, p = 0). The patient satisfaction score was 1.86 ± 1.17. The pain scores were 3.27 ± 1.17 for the FPNYL treatment (varied from 2 to 6). There were moderate erythema and oedema, which last for 3.84 ± 0.78 days. There were overall 68.18% (15/22) patients who felt pruritus in different degrees and 27.27% patients who encountered acne eruptions (white head type). No scar, hyperpigmentation or hypopigmentation was found. Conclusion: Treatment with fractional 1064 nm picosecond Nd:YAG laser is effective and safe for PAE of Chinese patients. [ABSTRACT FROM AUTHOR]

Copyright of Laser Technology is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Since the advent of the theory of selective photothermolysis, the importance of targeting the chromophore and minimizing the surrounding damage has been extensively discussed. Picosecond‐domain laser (ps‐laser) treatment with a wide range of wavelengths is an emerging option for various pigmented lesions; however, no definitive treatment choice has been confirmed. The authors aimed to investigate the efficacy and safety of a ps‐laser with a 785‐nm wavelength for the treatment of facial pigmented lesions in Asians. Three Korean patients with facial pigmented lesions were recruited for the study. A 785‐nm ps‐laser with a fractionated and an unfractionated handpiece was utilized to administer the treatment. The clinical outcome was evaluated by a clinician by comparing pre‐ and post‐treatment photographs. All patients exhibited a significant improvement in pigmented lesions including freckles, lentigines, and melasma, after three to four sessions of treatment. No adverse events, including post‐inflammatory hyperpigmentation or hypopigmentation were observed. In conclusion, this novel 785‐nm Ti:sapphire ps‐laser may be an effective and safe modality for treating pigmented lesions in skin of color. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms of light scattering and diffraction in random media is of great importance for random lasers, and can play a vital role in the efficient use of materials for optoelectronic devices and magneto-optical applications. Here, the effect of dynamic properties of dispersed magnetic (Fe3O4) nanofluids with different concentrations on the Gaussian laser beam passing through them was investigated, which involved the roles of magnetic field strength and response time factors. The results obtained showed that each of these two factors has a clear effect on the re-diffusion and distribution of nanoparticles (NPs), forming a layer of chains with different sizes. Moreover, it was found that the Fe3O4 NPs can be focused at the point of interaction with the laser beam. The transmittance of the laser beam decreased as a function of the magnetic field strength and response time until reaching a critical point, followed by changing the transmittance for a certain period of time until reaching a second critical point. Different laser beam shapes were achieved under the influence of the investigating factors, significantly changing the resulting scattering mean free path (SMFP). This variation behavior of SMFP can be used in many applications, including random lasers and light radiation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Combination of picosecond laser direct writing and characterization to study the properties of picosecond laser-modified SiC surface layers. • The evolution of the energy density in relation to the modified layer structure is revealed. • The reason for the sub-surface damage mechanism of picosecond laser modification is illustrated. • Laser modification can effectively reduce the hardness of silicon carbide and improve its machinability. The stable structure, high hardness, and brittleness of single-crystal 4H-SiC present challenges in achieving efficient and damage-free polishing processing. Ultra-short pulsed laser-induced surface modification provides a new solution to enhance the manufacturability of 4H-SiC. This paper aims to investigate the underlying mechanism of the picosecond laser-induced surface structural changes in 4H-SiC and the process of material removal from solid to vapour, elucidating the interaction mechanism between picosecond laser and 4H-SiC. A temperature gradient distribution model for picosecond laser irradiation on 4H-SiC was built to reveal the formation mechanism of subsurface crack damage. The results show that a combination of phase explosion and thermal effects controlled picosecond laser-modified 4H-SiC surfaces deposited spherical SiO 2 particles and the process. The study demonstrates that the cracking behaviour in the subsurface of picosecond laser-modified SiC predominantly occurs in the recast region. The fundamental cause of cracking is attributed to the tensile stresses generated by thermal effects and the volumetric changes in the molten material resulting from the overlapping of neighbouring spots in alternating hot–cold cycles. The nanoindentation demonstrated that laser modification can effectively enhance the machinability of SiC. The findings of this study can provide a theoretical basis for efficient non-destructive machining of hard and brittle materials. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy (LIBS) has been widely applied in various fields such as environmental monitoring, materials science, and archaeological research. The current research focuses on improving the spatial resolution of elemental spatial imaging by using LIBS. The nanosecond laser is commonly used in LIBS. During the nanosecond laser ablation process, there is a thermal effect on the target material, making it difficult to further improve the spatial resolution. This study used a picosecond laser to investigate the effects of the diameter of laser focusing spot, laser energy, and laser irradiation interval on the spatial resolution of LIBS. The spatial mapping of metallic coatings by using LIBS with a spatial resolution of 1 μm was achieved by using laser energy of 0.4 μJ/pulse and irradiation interval of 0.8 μm. The LIBS measurement results are in good agreement with the scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS) results. This research shows that by changing the laser ablation conditions, the spatial resolution of the spatial mapping of metallic coatings by using LIBS based on picosecond laser can be reduced to 1 μm or lower. [Display omitted] • Picosecond laser is used to improve spatial resolution of LIBS imaging technology. • The diameter of ablation crater is reduced through optimizing parameters. • LIBS imaging technology can achieve spatial resolution of 1 μm. • SEM-EDS measurements of the sample validated the LIBS imaging results. [ABSTRACT FROM AUTHOR]

[Display omitted] • Superhydrophobic & superoleophilic bronze surface by laser texturing and post-heating. • Post-heating enhanced adsorption of C–C(H) by bronze surface and increased CA. • Superolephilicity helps adsorption of lubricant, reduces bearing friction. • Superhydrophobicity enables anti-icing and self-cleaning. As a bearing material, bronze has high strength and hardness but is poor in anti-adhesion property. In this study, we propose a method to prepare a superhydrophobic and superoleophilic bronze surface by combining laser surface texturing and post-heat treatment. A picosecond laser was employed to produce pore arrays with varying spacings and depths on the bronze surface, which exhibited micro-nano hierarchical structures. A further post-heat treatment of the laser-textured sample at 150 °C in the ambient led to the formation of a superhydrophobic surface with a maximum water contact angle of 158° and with superoleophilicity. It was found that pore spacings played a significant role in forming the surface hierarchical structures, which were covered with the laser-ablated micro-nano particles. The pore depth, however, showed little influence on the surface wettability. Analysis of the surface chemical compositions by X-ray photoelectron spectroscopy (XPS) indicates that the C element mainly exists in the form of the C–C(H) group, which reduces the surface energy and leads to superhydrophobicity. It was also verified that the wettability transition of the bronze surface before and after heating was independent of the oxide transition. Rubbing tests were conducted to evaluate the durability of the surface hierarchical structure. Anti-icing and self-cleaning functions were demonstrated showing the potential of the developed method for preparing a superhydrophobic and superoleophilic surface. [ABSTRACT FROM AUTHOR]

Wide bandgap (WBG) materials have excellent semiconductor and physicochemical properties and are emerging materials. Silicon carbide (SiC) and gallium nitride (GaN), two representatives of third-generation semiconductor materials, can be used in high temperature, high voltage, high frequency, and high power applications. However, both materials are difficult to machine due to their brittle and hard properties. Laser processing is a suitable processing method, and in particular the unique non-thermal properties of ultra-short pulse laser processing have led to a wide range of applications in a variety of materials including ceramics, metals and biological tissues. WBG materials are third-generation semiconductor materials with broad application prospects in the semiconductor industry, but there are relatively few summarized studies on ultrashort laser processing of WBG materials. With this background, this paper reviews the application of ultra-short pulse lasers for the processing of two WBG materials, SiC and GaN. Laser-assisted processing, laser fabrication of microstructures and laser processing of difficult and complex parts are the three main components of ultrashort laser processing of SiC. Ultra-short laser processing of GaN, on the other hand, focuses mainly on laser lift-off and is used less for fabricating microstructures. Physical mechanisms of laser removal of semiconductor materials are summarized. Then, based on the classification of the pulse width, the applications of two types of ultrafast lasers, picosecond and femtosecond, for processing SiC and GaN materials are summarized. Finally, the paper concludes and discusses the existing ultrafast laser processing techniques for SiC and GaN materials and future perspectives. [ABSTRACT FROM AUTHOR]

Thanaporn Puaratanaarunkon, Pravit Asawanonda Division of Dermatology, Department of Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok, ThailandCorrespondence: Pravit Asawanonda, Division of Dermatology, Department of Medicine, Faculty of Medicine, Chulalongkorn University, 1873 Rama IV Road, Pathumwan, Bangkok, 10330, Thailand, Tel/Fax +662-2564253, Email Fibrosis@gmail.comBackground: Post inflammatory hyperpigmentation (PIH) is a sequela of laser procedures observed commonly in darker-skin individuals. In general, regular UV filters are beneficial in preventing PIH, but the comparison with sunscreen containing anti-inflammatory ingredients remains unexplored.Objective: To compare the efficacy of a sunscreen with anti-inflammatory agent (sunscreen A) in the reduction of PIH after a picosecond laser with that of regular sunscreen (sunscreen B).Methods: Fifty-nine acne vulgaris and acne scar patients with skin phototypes III and IV were treated with 1 session of picosecond laser with the microlens array to the whole face. Sunscreens A and B were randomized to be applied on either side of the face. Hyperpigmentation assessed by brown score mode on Visia®, acne quantity, porphyrins and patient satisfaction were evaluated at baseline, weeks 1, 2, 4 and 6.Results: Sunscreen A caused a higher reduction of the brown score compared to the other side but there was no statistically significant difference. Interestingly, a significant decrease of inflammatory acne lesions compared with baseline was observed as early as week 2 on the sunscreen A side (weeks 2, 4 and 6; P = 0.017, P = < 0.001, and P = < 0.001, respectively). Compared with sunscreen B, levels of porphyrins on sunscreen A side were significantly less at weeks 1 and 6 (weeks 1 and 6; P = 0.022 and P = 0.029, respectively).Conclusion: This study demonstrated a tendency towards lower post-laser pigmentation when the sunscreen with anti-inflammatory agents was applied. This product also had an effective outcome as an adjunctive treatment option of acne vulgaris.Thai Clinical Trials Registry ID: TCTR20210305004 (URL: http://www.thaiclinicaltrials.org/show/TCTR20210305004).Keywords: post inflammatory hyperpigmentation, picosecond laser, sunscreen, acne vulgaris, licochalcone A

Titanium alloy is widely used in different industrial applications. For the surface modification to improve the tribological properties, laser irradiation is a promising technology, which offers high efficiency, and high automation potential and geometrical flexibility. In this study, a novel method of surface modification for titanium alloys by carbonization using low fluence of laser irradiation in the atmosphere of PAO oil is proposed. Results show that the carbon content on the surfaces significantly increases with the laser shot number, with the laser irradiated spot showing little change of Ra. XPS analysis confirms that the carbon from the oil has bonded to the Titanium inside the alloy. By comparison with that irradiated without oil, the hardness of that irradiated in oil is much higher, demonstrating the feasibility of the surface modification of titanium carbide layer generation. To investigate the tribological properties, laser scanning irradiation in oil with different laser pulses were carried out to create laser modified areas and reciprocating ball-on-disk friction tests under oil lubrication were conducted. The laser modified areas show friction of 0.13, much lower than that of the unirradiated which is approximate 0.55, and the sliding lifetime of low friction is also increased with the laser pulse number. Moreover, by introducing patterning laser irradiation onto the uniformly irradiated area, the wear resistance can be further greatly improved, and the sliding lifetime can extend to 13 times of the optimal result of uniform irradiation.

With the development of aerospace and space scientific research, satellite laser ranging (SLR) has put forward higher requirements for response speed, data density, and measurement accuracy. In coaxial common optical path laser ranging, the emitted laser and the received laser echoes pass through the same optical system. Due to the reversibility of the optical path, the laser emission, monitoring, and laser echoes’ optical path all pass through the same optical system structure, and the response speed and ranging ability of the laser ranging system have been greatly improved. Based on the SLR system of the Shanghai Astronomical Observatory (SHAO), the laser transmitting telescope with an aperture of 21 cm was used to build a polarized coaxial SLR system. It uses a picosecond pulsed laser with a pulse repetition frequency of 2 kHz and a single-pulse energy of 2 mJ. Also, a 4f system was applied to shrink the laser echo beam and filter out noise, the measurements of low-Earth orbit and long-distance high-orbit satellites were realized, and the ranging accuracy was ∼2 cm. As far as we know, this is currently the smallest aperture telescope for SLR globally, which is conducive to the miniaturization and integrated development of SLR systems.

This study aims to induce a laser-induced periodic surface structure (LIPSS) on different coatings using a picosecond laser. An energy dispersive X-ray (EDX) spectroscopy analysis was performed, and wettability and friction tests were performed. Additionally, the surface electric field intensity (EFI) distribution was analyzed using the finite element method (FEM) to study LIPSS generation on different coating morphologies. The EDX results demonstrated that the LIPSS induced on the TiN coatings did not destroy them; however, the TiCN coatings were oxidized in the LIPSS fabrication process. The numerical simulation results indicated that the surface EFI and depth of the surface roughness were significantly linear, and the EFI was significantly related to the refractive index and extinction coefficient of the coating material. The wettability and friction test results implied that the LIPSS on different coatings could exhibit super hydrophilicity and played a role in friction reduction. • Laser-induced periodic surface structures (LIPSS) induced on different coatings. • TiCN coatings were oxidized in the LIPSS fabrication process. • Electric field intensity (EFI) and depth of surface roughness were linear. • EFI related to the refractive index and extinction coefficient of coating. • LIPSSs on different coatings exhibit super hydrophilicity and reduce friction. [ABSTRACT FROM AUTHOR]

In recent years, the demand for highly integrated and lightweight components has been rising sharply, especially in plastics processing. One strategy for weight-saving solutions is the development of conductive tracks and layouts directly on the polymer housing parts in order to be able to dispense with the system integration of additional printed circuit boards (PCB). This can be conducted very advantageously and flexibly with laser-based processes for functionalizing polymer surfaces. In this work, a three-step laser-based process for subsequent selective metallization is presented. Conventional injection molded components without special additives serve as the initial substrate. The Laser-Based Selective Activation (LSA) uses picosecond laser pulses to activate the plastic surface to subsequently deposit palladium. The focus is on determining the amount of deposited palladium in correlation to the laser and scan parameters. For the first time, the dependence of the metallization result on the accumulated laser fluence (Facc) is described. The treated polymer parts are characterized using optical and scanning electron microscopy as well as a contact-type profilometer. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, the design of surface pattering with the co-existence of micrometer and nanometer features was carried out to improve the arrayed surface structures on Ti/Cu/Ti and Ti/Cu/Zr/Ti multilayer thin films by picosecond laser processing. The novel composite structure consisted of two layers of Ti and subsurface distributed Cu and Zr layers (thickness of 10 nm) were deposited by ion sputtering on Si substrate to the total thickness of 300 nm. The changes in the composition, surface morphology, and wetting properties after laser modification was monitored by Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM–EDS), optical profilometry, and wettability measurements. It was found that laser irradiation can induce the melting of material with the formation of wrinkled periodic structures at the edges of the laser spots in both systems as a consequence of the hydrodynamic effects. Another interesting result was that the periodic structure in form of LSFL (low spatial frequency LIPSS) ripples was numerous but slightly pronounced in Ti/Cu/Zr/Ti, due to the presence of the Zr component as an ultra-thin subsurface layer, which most likely favored creating LIPSS. Such laser texturing has been used in the biomedical field as a method of developing surface topography, coated with oxides to potentially improve cell response via suitable surface wetting for a biological system. [ABSTRACT FROM AUTHOR]

Background: Clinical endpoints serve as an important guide to physicians during laser treatment. However, there are no reliable clinical endpoints for the fractional picosecond laser‐induced optical breakdown (LIOB) whose threshold is dependent on the irradiance of the laser and epidermal melanin content of the skin treated. Objectives: To determine the LIOB threshold in vivo of a 1064nm fractional picosecond laser for different skin colors. Methods: A cellular‐level resolution optical coherence tomography (OCT) has successfully demonstrated that the in vivo morphological change of LIOB in the epidermis by a fractional picosecond laser. By measuring the melanin content in the area of the skin to treat using a skin imaging device, the physician would therefore be able to determine the threshold of LIOB visually under OCT for the skin of that particular melanin content. Conclusion: The pilot study has demonstrated that OCT may serve as a non‐invasive modality to determine the thresholds of LIOB by a fractional picosecond laser. And the established correlation between melanin content and LIOB threshold in this pilot study may further guide physicians, that is, physicians may be able to predict the threshold of LIOB, without having to see the clinical endpoints, by simple measurement of melanin content of the skin to treat preoperatively. [ABSTRACT FROM AUTHOR]

Objectives: Picosecond lasers with a microlens array can cause laser-induced optical breakdown (LIOBS) and LIC (Intradermal laser-induced cavitation) within high-fluence areas. This study aimed to describe the clinical, reflectance confocal microscopy (RCM), histopathological findings, and the characteristics of vacuoles caused by LIOBS and LIC in individuals with skin types III and IV., Materials and Methods: This study was performed on six Chilean healthy volunteers, males and females, aged 35-65 years old with Fitzpatrick skin phototypes III-IV. The laser was applied in the inner proximal area of the nondominant arm. RCM evaluation was performed 24 h later; 48 h later, skin biopsies were performed on the laser-treated areas. Clinical, histological, and RCM findings were recorded., Results: Every individual developed a 10 mm 2 area of clinical erythema in the treated area. Under RCM, all six volunteers had hyporeflective spherical structures at the level of the epidermis, consistent with intraepidermal vacuoles. Histopathological evaluation revealed different sizes of vacuoles in both the epidermis and dermis., Conclusion: The LIOBS and LIC processes and the secondary production of vacuoles could be highly valuable for effective dermal remodeling treatment and aid in promoting the production of new collagen, elastic fibers, and growth factors that could improve skin texture. These structures were visible under RCM and histopathological evaluation., (© 2024 Wiley Periodicals LLC.)

Background/objective: Laser therapy has emerged as a widely favored treatment option for solar lentigines (SL). However, a significant challenge associated with this treatment, particularly among individuals with darker skin tones, is the notable risk of postinflammatory hyperpigmentation (PIH) induction. In response to these concerns, the authors conducted a prospective, self-controlled study to comprehensively evaluate the safety and effectiveness of 532-nm picosecond laser, both with and without a microlens array (MLA), for the management of SL in patients with Fitzpatrick skin types (FST) III-V., Methods: Twenty-seven patients with FST III-V and bilateral SL on the face underwent randomized treatment. One side of the face was treated with a 532-nm picosecond laser coupled with an MLA, utilizing the fractional pigment toning (FPT) technique, while the other side received treatment without the MLA, following the conventional technique (CT). The FPT technique utilized a 9-mm spot size with a fluence of 0.47 J/cm 2 for two passes covering 40% of the area. In contrast, the CT used a 4.5-mm handpiece with fluence ranging from 0.3 to 0.7 J/cm 2 . Patients received a single treatment and were evaluated for pigment clearance, occurrence of PIH, and other adverse effects at 2 weeks, 1, 3, and 6 months posttreatment., Results: Twenty-seven participants completed the study protocol. Analysis of pigment clearance, measured via 3D photography, showed significant improvement from 2 weeks to 6 months posttreatment for both the FPT technique (p < 0.001) and CT (p = 0.004). PIH occurred in 64%, 80%, 96%, and 88% of cases on the CT side, compared to 8%, 32%, 36%, and 16% on the FPT technique side at 2 weeks, 1, 3, and 6 months posttreatment, respectively. The incidence of PIH was significantly lower on the FPT technique side compared to the CT side throughout the follow-up periods. Additionally, transient and mild hypopigmentation occurred in one participant (4%) on the FPT technique side and in five participants (20%) on the CT side. No other adverse effects were observed during the study., Conclusions: The 532-nm picosecond laser emerges as a safe and efficacious treatment modality for SL in individuals with FST III-V. Particularly noteworthy is the efficacy of the FPT technique, which demonstrates comparable effectiveness while significantly reducing the incidence of PIH compared to the CT., (© 2024 The Author(s). Lasers in Surgery and Medicine published by Wiley Periodicals LLC.)

Rongxin Ren, Shiwei Bao, Wenjiang Qian, Hongyi Zhao Department of Plastic Surgery, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, People’s Republic of ChinaCorrespondence: Hongyi ZhaoDepartment of Plastic Surgery, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, People’s Republic of ChinaTel/Fax +86 10 65238573Email zhaohongyi991@yeah.netObjective: Post-inflammatory hyperpigmentation (PIH) is a reactive hypermelanosis of various skin types, which occurs as a sequela of cutaneous inflammation or injury. Despite generally a self-limited and temporary condition, PIH is still a frustrating problem that can have significant psychosocial effects on patients, especially those with darker skin types. Laser therapy is one of the effective treatments for PIH, and various wavelength lasers and light devices have been utilized in PIH therapy. Nonetheless, data on the long-term efficacy of the 755-nm alexandrite picosecond laser are limited.Methods: This study analyzed two cases of PIH treated with a combination of a 755-nm alexandrite picosecond laser and a diffractive lens array or zoom handpiece. Efficacy of the treatment was determined by the images of skin lesions under a fixed light source before and after each treatment, which were independently reviewed by two plastic-surgery specialists blinded to the clinical data. Improvement was classified as complete (> 75%), significant (50– 75%), mild (25– 50%), and inefficient (< 25% or no obvious change). Skin imaging analysis was carried out using the VISIA system (Canfield, USA), and dermoscopy was performed at the same time.Results: After two to three courses of treatment, all cases showed significant or complete improvement, and no recurrence was observed during the three years of follow-up.Conclusion: A 755-nm alexandrite picosecond laser in combination with a diffractive lens array or zoom handpiece had significant and long-term efficacy for the treatment of PIH caused by trauma. However, attention should be paid to the problem of transient deepening of pigmentation during treatment.Keywords: 755 nm, picosecond laser, long-term effect, post-inflammatory hyperpigmentation

Yan Qu,1 Xien Feng,2 Jin’ning Liang,2 Junru Liu,3 Dong Gao2 1Department of Dermatology, The Affiliated Hospital of Weifang Medical University, Weifang, Shandong, 261031, People’s Republic of China; 2Department of Dermatology, Yantai Yuhuangding Hospital, Yantai, 264003, Shandong, People’s Republic of China; 3Department of Dermatology, Yantai Yuhuangding Hospital Laishan Branch, Yantai, 264003, Shandong, People’s Republic of ChinaCorrespondence: Dong Gao Email gaodong_yhd@163.comObjective: We aimed to investigate picosecond laser effects regarding rat tattoo removals. We systematically detected the metabolic pathways considering tattoo pigment particles in rat models.Materials and Methods: We employed fluorescein to mark the tattoo dye and utilized a pattern needle to prepare tattoo on rat so as to establish the tattoo removal effects of picosecond laser methods employing animal models. We applied a picosecond laser to process the tattoo and observed the effects along with metabolic pathways for tattoo removal via pathology and imaging approaches.Results: Based on the results of characterization, pathology and fluorescence, we discovered that the picosecond laser could effectively remove the pigment particles on rat skin, part of which would be metabolized out of the body through the circulatory system. After picosecond laser treatment, the fluorescence intensity of the rat skin engraved part was gradually weakened. At 8 h after the treatment, the metabolic organs had weak fluorescence, and there was no fluorescence in the metabolic organs at 12 h and 24 h after the treatment.Conclusion: The picosecond laser had perfect tattoo removal effects, which could be utilized as a reference for clinical tattoo removal.Keywords: tattoo, picosecond laser, pattern engraving, dye

Satellite laser ranging (SLR) had been operated at a pulse repetition frequency (PRF) from ∼10 Hz to 10 kHz; the ultra-high PRF of SLR (UH-SLR) is a trend of development. In this study, an alternate working mode of laser firing and gated pulse bursts is proposed to solve the problem of laser echo interference by laser backscattering. Through an ultra-high PRF of 200-kHz picosecond green laser with single-pulse energy of 80 μJ and a pulse width of 10 ps and a ranging gate device, UH-SLR has been built by an aperture of the 60-cm SLR system in the Shanghai Astronomical Observatory. By this UH-SLR, low-orbit to high-orbit and geostationary orbit satellites are measured night and day and also for low-orbit and medium-orbit satellites in the daytime. The normal point (NP) accuracy is ∼30 μm for low-orbit satellites and ∼100 μm for high-orbit satellites, which provides an effective method for the development of ultra-high PRF and high-precision space target laser ranging.

In the introduction, we present an overview of previous research on this subject in order to help the reader review possible technological solutions regarding the joining of construction materials. The original research presented in this article concerns the results of increasing the shear strength of adhesive joints of plastics using various types of surface preparation (laser texturing). Laser texturing consists in developing the surface by applying various geometric patterns of appropriate shapes and depths, as well as its density on the surface. The above parameters are currently selected in an empirical way as research is still being developed as part of a research project. The textures obtained in this way are subjected to microscopic examination. Then, a layer of glue is applied, and the samples prepared in this way, after drying, are subjected to various destructive tests, e.g., tensile, shear, and bending. In this article, we attempted to test the strength of the bonded joint of polyethylene (PE). The impact of a laser beam with ultrashort picosecond pulses was used in the research. Tools in the form of a TRUMPF TruMicro 5325c device integrated with a SCANLAB GALVO scanning head were used. This enabled ablative material removal without the presence of a heat affected zone (HAZ) in the non-laser part. Ultrashort laser pulses remove material without melting the non-exposed area by the laser beam. On the basis of the tests performed (in this article and previous research works of the authors), it was shown that the method increases the shear strength of the glued joints made in the tested construction materials. This is confirmed by laboratory results of tribological tests. The laser treatment parameters used, which are shown in this article, did not lead to the appearance of cracks in the micromachined materials. Research has shown that the connections between elements with a properly selected micropattern are characterized by a several-fold increase in the strength of joints, unlike materials without a micropattern. The presented method may be helpful for use as a technology for joining plastics.

To mitigate the challenges pertaining to coating damage and processing defects arising from the utilization of ultrafast laser drilling for microhole creation in thermal barrier coatings (TBCs), thereby exerting substantial influence on the long-term durability of these microholes, the investigation proposes a comprehensive methodology. It encompasses the design of a two-factor four-level full factorial experiment and the execution of experimental research on picosecond laser drilling of TBC microholes. By meticulously analyzing the morphology of the microholes and the coating interface, the damage mechanisms associated with picosecond laser drilling of TBC microholes, as well as the influence of laser process parameters on coating damage, are revealed. The findings reveal that the optimal microhole entrance quality and the lowest roughness along the hole perimeter are attained at a laser power of 12 W and a scanning speed of 320 mm/s. Moreover, at a laser power of 30 W and a scanning speed of 320 mm/s, the minimal crack length on the blunt angle side of the hole and the highest machining quality are observed.

Laser-induced graphene (LIG) has gained considerable attention recently due to its unique properties and potential applications. In this study, we investigated using LIG in polyimide (PI) as a material for antenna applications. The LIG-−PI composite material was prepared by a facile picosecond laser (1064 nm) irradiation process, which resulted in a conductive graphene network within the PI matrix. Furthermore, LIG formation was confirmed by Raman spectroscopy and sheet resistance measurements. Finally, a patch antenna from LIG with 2.45 GHz microwaves was simulated, produced and tested. These findings suggest that LIG−PI composites have great potential for use in high-frequency electronic devices and can provide a new avenue for the development of flexible and wearable electronics.

Background: Removal of the unwanted tattoo was initially focused treatment of picosecond laser in the setting of the unfractionated beam, whereas the fractionated 1064‐nm picosecond lasers (Fr‐Pico) has been successfully utilized in various skin conditions, including scar and benign pigmented lesions. However, no studies compared the combination of Fr‐Pico and unfractional 1064‐nm picosecond laser (UFr‐Pico) and UFr‐Pico alone in tattoo removal. Objective: This study aims to compare the efficacy and safety of the combination of Fr‐Pico and UFr‐Pico and the UFr‐Pico and in tattoo removal. Materials and methods: Nineteen black tattoos in 11 patients were treated with UFr‐Pico on one half and in combination with Fr‐Pico on another half over three sessions with 4‐week intervals and 4‐week follow‐up after the last session. Treatment efficacy was assessed using digital photographs, skin imaging analysis, and patient satisfaction. Results: After three treatments, tattoo clearance scores revealed that greater than 50% clearance was achieved in 11 (84.6%) tattoos treated with combination side and 9 (69.2%) tattoos with UFr‐Pico alone. Significant differences were observed between the groups at 8 and 12 weeks. Skin textural changes also demonstrated significant improvements in the combination side at Week 12. Adverse events, such as blistering and textural changes, were fewer in the combination side. Conclusion: The combination of 1064 nm Fr‐Pico and UFr‐Pico may be more effective and safer in tattoo removal than UFr‐Pico alone. [ABSTRACT FROM AUTHOR]

In this study, the diamond-like carbon (DLC), a tetrahedral amorphous carbon sample deposited on Si, was irradiated using a picosecond laser. We evaluated the picosecond-laser-induced structural and morphological changes in DLC using micro-Raman spectroscopy via line measurements. We obtained the spatial distribution of the structure and morphology of DLC on Si by regression analysis of the Raman spectra. The photo-induced crater could be categorized into four regions: peripheral, morphological-change, structural-changes, and ablated regions. The structure and morphology of the peripheral region were similar to those of the as-received DLC. In the morphological-change region, which is inside the periphery region, the thickness of the DLC decreased without any structural changes. At the center of the crater, which is shown in black in the optical image, two regions were identified by Raman spectroscopy. On the outer side, there is a structural-change region where the graphitization of DLC materialized with a reduction in the film thickness. Inside the structural-change region, there is an ablated region where the DLC was degraded by laser ablation. [ABSTRACT FROM AUTHOR]

In laser processing, due to the short interaction time between an ultrashort pulse laser and silicon, it has been difficult to study the lattice temperature change characteristics of silicon. In this paper, the interaction between a picosecond laser and silicon was studied. Based on the Fokker–Planck equation and two-temperature model (TTM) equation, a simulation model of silicon heating by different pulse-width picosecond lasers was established. The results show that within the range of 15 to 5 ps, the maximum lattice temperature tended to increase first and then decrease with the decreasing pulse width. The watershed was around 7.5 ps. The model error was less than 3.2% when the pulse width was 15 ps and the single pulse energy was 25 μJ. [ABSTRACT FROM AUTHOR]

Objective To explore the efficacy and safety of 755nm picosecond laser in the treatment of freckles accompanied by melasma. Methods From June 2018 to December 2020, 73 patients with facial freckles accompanied by melasma were recruited in this retrospective clinical study. All patients with freckles of type III to IV Fitzpatrick's classification accompanied by melasma were treated by 755 nm picosecond laser. The clearance of freckles, melasma area and severity index (MASI) at 3 months after treatment was assessed by VISIA. Results All patients were followed up for 3 months. The average clearance scores of freckles in all patients were (2.53±0.50). The scores of MASI decreased from (10.62±0.19) before treatment to (10.38±0.19) after treatment. The post-inflammatory hyperpigmentation occurred in 2 patients (4.8%). No obvious adverse reactions occurred in remaining patients. Conclusion The 755 nm picosecond laser is a safe and effective method to treat freckles accompanied by melasma. This method can effectively remove freckles and reduce melasma. The tolerance of treatment process is good. No serious adverse reactions are observed. The risk of exacerbation of melasma is relatively low. [ABSTRACT FROM AUTHOR]

To effectively improve the cutting quality of sapphire and optimize ultrafast picosecond laser cutting technology, this paper presents a new numerical simulation method and an experimental study of the ultrafast double-laser cutting of sapphire materials. The optimal cutting technology and the numerical simulation of the temperature field of the ultrafast picosecond laser cutting of sapphire were designed independently. The principle is based on double-laser-beam cutting using an ultrashort pulse and a CO2 beam; the ultrashort pulse is focused on the material through a laser filamentous cutting head and perforated, and it moves at a speed of up to 200 mm/s to form the desired cutting line. Then, a CO2 beam is used for heating, and the principle of heat bilges and cold shrink causes the rapid separation of products. Furthermore, an SEM tester was used to characterize and analyze the microstructure and properties of sapphire materials. A microscope was used to analyze the composition of the cutting micro-area and explore the general mechanism of laser cutting sapphire. The results showed that the proposed method greatly improves efficiency and precision; in addition, the chipping size of sapphire is less than 4 μm. [ABSTRACT FROM AUTHOR]

Melasma is an acquired, chronic skin pigmentation disorder that affects mainly women and can significantly affect the quality of life and self-esteem of patients. Many therapeutic procedures have been described in the literature, nevertheless the disease is difficult to treat. A case report. The paper presents a case of successful laser treatment in a 44-year-old woman with a long history of facial skin discoloration of the type of melasma. The patient was treated with combined laser therapy in the area of ​​facial discoloration with a picosecond laser and a thulium laser. Aim The aim of this study is to draw attention to the possibility of using laser therapy in the treatment of melasma-type skin hyperpigmentation. In this article, we describe a case of brightening of a melasma-type discoloration during a single laser treatment combining the use of a 1064nm picosecond laser and a 1927nm thulium laser, in order to meet interests of patients and physicians in the use of laserotherapy in the treatment of discoloration, especially in patients who do not tolerate well the side effects of pharmacological therapies. Conclusions. The use of laser therapy, with particular emphasis on the picosecond and thulium laser, can be an important and effective element in the treatment of melasma-type hyperpigmentation of the skin.

Picosecond fiber laser was subjected on surface of ductile cast iron to induce graphene-like micro-texture array and enhance the tribological properties. The size of the dimples was regulated in the range of 5 μm–110 μm. The in-situ fabrication process was carried out on the workpiece surface in parallel manner and the scanning speed can be up to 3 m/s. The formation mechanism of graphene-like structure was analyzed. The tribological properties of the textured samples were investigated using a ball-on-disk tribometer. The results showed that the laser textured samples exhibit low coefficient of friction and the anti-wear properties were improved significantly. The textured sample showed no distinct wear pit, while the non-textured sample showed typical wear pit with depth up to 15 μm. Volume wear rate was reduced by 69.6 ± 6.9%. The graphene-like micro-texture array conducted by picosecond fiber laser scanning will not change the material isotropic, and the improved tribological properties are attributed to the combined effects of the increased surface hardness, improved heat dispersion property and entrapment of wear debris.

• Metal film on a metal substrate can be selectively removed by picosecond laser. • Fabricated holes and lines show the very nice surface morphologies. • Depth of the fabricated holes and lines is identical with the thickness of the film. • Unlike the metal film on a glass substrate no undesired cracks are produced. Laser micromachining is a convenient technique to structure and/or functionalize the surfaces of various materials. The use of ultrashort laser pulses has an obvious advantage to minimize the heat effect, which results in the formation of a hole without rims. Nevertheless, it is still difficult to fabricate a line without rims even with ultrashort laser pulses, because multiple irradiation of ultrashort laser pulses with a sufficient spatial overlap promotes the formation of rims and undesired structures. In this work we employ a metal substrate with a thin metal film, and demonstrate the fabrication of depth-controlled high quality lines, not to mention holes, through the selective removal of the film by picosecond laser pulses without forming rims and undesired structures. Morphological study of the target surface reveals that the fabricated structures have unprecedentedly flat bottoms with nearly vertical sidewalls to the surface. [ABSTRACT FROM AUTHOR]

The fabrication of microstructure on metal surface by laser processing technology will damage the surface integrity. In this research, picosecond laser was used to fabricate microstructure on the surface of TC-4 alloy, and the surface integrity was protected by adjusting parameters. The results show that using 0.6W power, 100mm/s scanning speed, 700kHz pulse frequency and 0.1ms point engraving time can avoid the influence and remodeling of the structure when the laser removes the material. In addition, the surface integrity after material removal is improved by ultra-low power and ultra-high speed laser cleaning process. [ABSTRACT FROM AUTHOR]

Objectives: Laser therapy has become one of the mainstay treatments for improving signs of aging including wrinkles, large pores, and skin pigmentation. However, in patients with pigmented skin, an increase in complications including post‐inflammatory hyperpigmentation (PIH) has been noted. The purpose of this study is to investigate not only the safety profile of 755‐nm picosecond laser with diffractive lens array (DLA) at approximately 2250 pulses on the face in people with darker skin, but also to evaluate its efficacy in treating wrinkles and pore sizes after one treatment session among different age groups. Methods: This single‐center, retrospective study enrolled patients between age 22 and 65 with both facial wrinkles and enlarged pore sizes. A total of 46 patients (7 male, 39 female, mean age 43) with Fitzpatrick skin types III and IV were enrolled. Two independent data‐blinded dermatologists assessed and scored the improvements of patients' wrinkles and pore sizes using photographs. Results: After one treatment session, statistically significant improvements were observed in lateral canthal wrinkles (p < 0.001) and facial wrinkles (p = 0.014). In addition, greater percentage of the patients from the aged group (50–65 years) showed clinically significant improvement as compared with the younger group. Conclusions: For patients with type III and IV skin, one session of DLA picosecond laser treatment at around 2250 pulses to the face is safe and effective for clinically meaningful improvement of the wrinkles and pore sizes, especially for the patients from 50‐ to 65‐years of age. [ABSTRACT FROM AUTHOR]

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In this study, the cutting of borosilicate glass plates in ambient air and water with a 355 nm wavelength picosecond laser was carried out. Low (2.1–2.75 W) and high (15.5 W) average laser power cutting regimes were studied. Thorough attention was paid to the effect of the hatch distance on the cutting quality and characteristic strength of glass strips cut in both environments. At optimal cutting parameters, ablation efficiency and cutting rates were the highest but cut sidewalls were covered with periodically recurring ridges. Transition to smaller hatch values improved the cut sidewall quality by suppressing the ridge formation, but negatively affected the ablation efficiency and overall strength of glass strips. Glass strips cut in water in the low-laser-power regime had the highest characteristic strength of 117.6 and 107.3 MPa for the front and back sides, respectively. Cutting in a high-laser-power regime was only carried out in water. At 15.5 W, the ablation efficiency and effective cutting speed per incident laser power increased by 16% and 22%, respectively, compared with cutting in water in a low-laser-power regime. [ABSTRACT FROM AUTHOR]