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Background Aims Methods Results Conclusions The picosecond neodymium yttrium aluminum garnet laser (PNYL) has been successfully used in treating acquired bilateral nevus of Ota‐like macules (ABNOM). The 730‐nm picosecond titanium sapphire laser (PTSL) is an emerging tool for pigmentary disorders. However, no studies have compared two different wavelengths of picosecond laser for the treatment of ABNOM.To compare the efficacy and safety of the 730‐nm PTSL with the 1064‐nm PNYL in the treatment of ABNOM.Fifteen participants with ABNOM were randomized to undergo a single session of either the 730‐nm PTSL on one side of the face and 1064‐nm PNYL on the other side. Efficacy and safety assessments were performed by blinded visual evaluations at baseline, 12 weeks, and 24 weeks posttreatment. Participants' satisfaction and adverse effects were recorded.Compared to baseline, The 730‐nm PTSL‐treated side showed better improvement than that of the 1064‐nm PNYL‐treated side at 24 weeks posttreatment (1.67 ± 1.047 vs. 0.87 ± 0.640, p = 0.027). There were no significant differences in pain sensation and participants' satisfaction between the two laser treatments.The 730‐nm PTSL is more effective than the 1064‐nm PNYL in the treatment of ABNOM. [ABSTRACT FROM AUTHOR]

This brief report discusses the challenges in treating dermal melanosis and the limitations of current laser treatments due to inadequate tissue penetration and potential side effects. It introduces laser-induced optical breakdown (LIOB) as a novel therapeutic approach using a picosecond laser with a diffractive lens array (DLA) to target dermal pigmentation effectively. LIOB induces multiphoton ionization, leading to melanin clearance through phagocytosis and apoptotic cell removal, while also promoting dermal remodeling and collagen synthesis. We present a case of successful treatment of dermal pigmentation in a 55-year-old woman using 755 nm-picosecond alexandrite laser therapy, demonstrating significant improvement without recurrence. The findings suggest that LIOB offers a promising solution for acquired dermal hypermelanosis by addressing both diffuse and localized pigmentation effectively, leading to skin rejuvenation with minimal downtime and high patient satisfaction. [ABSTRACT FROM AUTHOR]

The picosecond laser was utilized to fabricate the slanting microholes efficiently on SiC/SiC ceramic matrix composites. The machining damage, material oxidation, and temperature field were mainly analyzed through static and in-situ detections. The damage evolution and ablation behavior of SiC/SiC composites were qualitatively and quantitatively revealed. The results showed that the lowest peak temperature of the slanting microhole was 282.6 °C. The heat accumulation effect and thermal stress that was tensile stress in nature present caused recasts, microcracks, fiber fracture, fiber debonding, and fiber stripping. Fibers and matrix underwent slight oxidation, forming SiO 2 recasts through the phase transition. The pulse energy, frequency, and inclination angle regularly affected the quantity, size, and distribution of microcracks, material removal rate (MRR), and hole wall roughness. The maximum MRR was about 2.5 mm3/s, corresponding to the minimum time was 0.9 s. The circularly polarized picosecond laser could process parallel striped laser-induced periodic surface structures (LIPSS) on the hole wall. • The damage evolution and ablation behavior of picosecond laser high-efficiency ablation of 2.5D SiC/SiC composites were revealed. • Thermal stress existed in the ablation of SiC/SiC composites by picosecond laser, and its essence was tensile stress. • It was found and explained that the circularly polarized picosecond laser fabricated parallel striped HSFL on SiC/SiC composites. • Picosecond laser ablation of slanting microhole structures in SiC/SiC composites with high efficiency, low oxidation, and high quality has been realized. [ABSTRACT FROM AUTHOR]

Background: Fractional picosecond lasers (FPL) are reported to be effective and safe for atrophic acne scars and post‐acne erythema. However, there is no evidence regarding the effectiveness and safety of FPL treatment for non‐acne atrophic scars and scar erythema among Chinese patients. Methods: In this retrospective study, 12 Chinese patients with non‐acne atrophic scars, including nine with scar erythema, were treated with one to three sessions of 1064 nm FPL treatment. Clinical improvement was objectively assessed through blinded evaluations by external physicians. A modified Manchester Scar Scale (mMSS) and the Clinician Erythema Assessment Scale (CEAS) were individually used to evaluate atrophic scars and scar erythema based on photographs. Physician‐assessed and subject‐assessed Global Aesthetic Improvement Scale (GAIS) were used to assess changes before and after FPL treatment. Patient satisfaction and adverse events were also documented. Results: Total mMSS scores, as well as three parameters (color, distortion, and texture), were significantly decreased after FPL treatment, with a mean reduction of 3.18 ± 1.60 in total scores (p < 0.05). The CEAS scores were significantly reduced from 2.41 ± 0.98 before treatment to 0.41 ± 0.40 at the final visit (p < 0.05). Based on physician‐assessed and subject‐assessed GAIS scores, 11 (91.7%) patients were improved after FPL treatment. 33.3% of patients were very satisfied, and 41.7% were satisfied. No serious, prolonged (> 3 weeks) adverse events were observed. Conclusion: Our study suggests that 1064 nm FPL treatment may be a promising option for non‐acne atrophic scars, especially with scar erythema. Further studies are needed to confirm our results. [ABSTRACT FROM AUTHOR]

In this study, a picosecond (ps) laser (wavelength 532 nm) with a top-hat beam was used to ablate a dielectric stack on a polished surface to improve the quality of the ablated surface. Homogeneous removal was achieved at an appropriate fluence for the ablation, since the uniform absorption of laser energy in the stack occurred by using a top-hat beam and a polished surface process. When the fluence was in the range of 0.51–0.74 J/cm2 for a top-hat beam, the direct ablation played a leading role, since more energy was absorbed in the stack rather than in the silicon, resulting in minimum damage. However, the surplus peak fluence of a ps laser with a Gaussian beam penetrated the stack and consequently caused heat shock to the silicon, and partial lift-off ablation generated thermal damage with a depth of more than 2 μm. Average efficiency of 23.40% for the passivated emitter and rear contact (PERC) cells applied with the superior ablation exceeded that for the reference cells applied with the nanosecond laser ablation with a Gaussian beam by 0.11% absolute. The significant improvement of open-circuit voltage (Voc), short-circuit current (Isc) and fill factor (FF) was mainly due to the reduced recombination at the rear contacts and decreased leakage current. The mechanisms of the laser ablation with a top-hat beam resulting in reduced damage are also applicable to other lasers with different wavelengths and can be used for improving the efficiency of other cells where a low level of damage in the ablation process is needed to decrease the surface recombination. [ABSTRACT FROM AUTHOR]

Melasma is a common condition of hyperpigmented facial skin. Picosecond lasers are reported to be effective for the treatment of melasma. We aimed to identify the most effective therapeutic mode and elucidate the potential molecular mechanisms of picosecond lasers for the treatment of melasma. Female Kunming mice with melasma‐like conditions were treated using four different picosecond laser modes. Concurrently, in vitro experiments were conducted to assess changes in melanin and autophagy in mouse melanoma B16‐F10 cells treated with these laser modes. Changes in melanin in mouse skin were detected via Fontana–Masson staining, and melanin particles were evaluated in B16‐F10 cells. Real‐time polymerase chain reaction and western blotting were used to analyse the expression levels of melanosome and autophagy‐related messenger ribonucleic acid (mRNA) and proteins. A combination of large‐spot low‐fluence 1064‐nm and fractional 1064‐nm picosecond lasers resulted insignificant decreases in melanin as well as in mRNA and protein expression of melanin‐synthesizing enzymes (TYR, TRP‐1 and MITF). This combination also led to increased expression of the autophagy‐related proteins, Beclin1 and ATG5, with a marked decrease in p62 expression. Intervention with the PI3K activator, 740 Y‐P, increased TYR, TRP‐1, MITF, p‐PI3K, p‐AKT, p‐mTOR and p62 expression but decreased the expression of LC3, ATG5 and Beclin1. A combination of large‐spot low‐fluence 1064‐nm and fractional 1064‐nm picosecond lasers proved more effective and safer. It inhibits melanin production, downregulates the PI3K/AKT/mTOR pathway, enhances melanocyte autophagy and accelerates melanin metabolism, thereby reducing melanin content. [ABSTRACT FROM AUTHOR]

High precision polycrystalline diamond (PCD) micro cutting tools with complex geometrical features which widely used in the field of aerospace, automotive, electronics, etc. are difficult to fabricate by traditional processes. Ultrashort pulse laser (ULPL) with extremely high peak power and short pulse duration is the ideal tool for processing PCD materials. In this study, an industrial picosecond laser source with the wavelength of 1064 nm and the pulse duration less than 10 ps was used to fabricate PCD micro drills. A graphical user interface (GUI) and a computer-aided manufacturing (CAM) module have been developed. A twist PCD micro drill with a diameter of 0.75 mm was successfully fabricated by picosecond pulsed laser roughing and grinding finishing. The mechanisms of ablation removal and surface integrity generation in picosecond pulsed laser processing of PCD materials were discussed. The results show that PCD micro drills roughed by a picosecond pulsed laser have sharp geometric edges. The thickness of thermal damage layer induced by the picosecond pulsed laser is very small, which could be completely removed in the grinding finishing process. Compared to conventional grinding, the fabricate time of PCD micro drill based on the newly proposed method is reduced by 48.2%. [ABSTRACT FROM AUTHOR]

Polycrystalline diamond (PCD) is an excellent material for machining micro-tools due to its high hardness and wear resistance. However, the diameter of micro-milling tools is generally required to be less than 500 μm. When preparing micro-milling tools with a large aspect ratio, the processing load introduced by traditional grinding methods is easy to cause tool fracture. Therefore, a composite structure of carbide tool holder and diamond tool head is proposed in this paper. A technique of picosecond laser machining PCD micro-milling tool was studied, and the overall manufacturing process of tool blank preparation, nanosecond laser roughing and picosecond laser finishing was formed. A two-dimensional ablation mathematical model for tangential machining of PCD with a multi-pulse picosecond laser was established, and experiments verified the reliability of the mathematical model. In addition, the effects of picosecond laser pulse pitch, pulse energy, and track spacing on the surface quality of PCD materials with different particle sizes and cutting edge radius were studied by orthogonal experiments. The results showed that after picosecond laser processing, the surface roughness (Sa) of PCD with a particle size of 2 μm was the best, which can reach 0.33 μm, and the cutting edge radius of PCD micro-milling tool with a particle size of 25 μm was the smallest, which can get 1.67 μm. Using the optimized picosecond laser parameters, the high-sharpness single-edge micro-milling cutters with different particle sizes PCD with a diameter of 100 μm, aspect ratio greater than 3, and a cutting edge radius less than 3 μm were successfully fabricated. [ABSTRACT FROM AUTHOR]

During the grinding process, K9 optical glass exhibits poor machinability, leading to issues such as crack growth, machining costs, low machining efficiency, and many other problems, seriously restricting its manufacture and application. This paper evaluated the feasibility of picosecond laser-assisted polishing of optical glass workpieces as an economical production method. This study involves a comprehensive exploration of several key aspects, including workpiece dimension control, the surface quality after picosecond laser ablation assessment, the parameters of the picosecond laser equipment optimization, and fine-tuning the parameters of the polishing equipment. The results show that the workpiece surface exhibits a recast layer with an uneven thickness distribution after laser processing, leading to a 38% reduction in luminous flux. Additionally, the roughness of the ablated surface decreases as the pulse repetition rates increase from 40 to 120 kHz. Due to the nonlinear absorption of energy by the amorphous body, the maximum ablation depth occurs around 80 kHz. Furthermore, the unevenly distributed recast layer affects the polishing process. Nevertheless, the efficiency of the picosecond laser-assisted polishing method is greatly improved compared to the conventional method of precision grinding followed by polishing. [ABSTRACT FROM AUTHOR]

This article shows the effective clearance and safe treatment for a novel Picosecond Laser with shortest pulse width in treatment sessions with 4 patients. Conclusion: Picosecond lasers with very short pulse length can enable a more effective and painless treatment than nanosecond Lasers for black and colored tattoos and in some cases, it is possible to clear tattoos with fluences of a lesser scale than with nanosecond domain pulses. Our cases show better clearance in less treatment sessions compared to other lasers with which we have gained experience in our practice. The MOA (Mechanism of action) allows a safe and effective treatment with lower fluences, as a result decreasing the thermal energy transfer to surrounding tissues and minimizing the risk of scarring and reducing the patient’s pain. [ABSTRACT FROM AUTHOR]

The propagation of spherical shock waves through metallic mediums have been considered in this paper. The effect of overtaking disturbances in the propagation of spherical shock waves through solids, especially metals such as Aluminium and Copper, has been analysed by employing Chisnell-Chester-Whitham method. Under the influence of spherical shock waves flow variables have been obtained analytically as well as estimated numerically. Expressions for the pressure and the particle velocity behind the shock wave have also been obtained. It is found that shock strength in both the metals decreases as shock propagates through them. Shock velocity and modified shock velocity depict a decreasing pattern with increasing propagation distance. These observations suggest many industrial and medical applications of shock waves. [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. [ABSTRACT FROM AUTHOR]

The absolute concentration and spatial distribution of ground-state atomic nitrogen (N) in an atmospheric pressure plasma jet were measured using the two-photon absorption laser-induced fluorescence. The jet was ignited by radio frequency voltage in argon (or argon with nitrogen admixture) flowing through a silica tube. The spatially resolved measurements of atomic nitrogen concentration were realized in the effluent of the jet. In a pure argon plasma, the N concentration was increased with the distance from the silica tube and reached the maximum value ( 3.5 ⋅ 10 14 cm−3) at the distance of 15 mm, and then sharply decreased at the end of the plume. On the contrary, plasma ignited in Ar with nitrogen admixture, the maximum N concentration was located directly at the end of the silica tube, where plasma starts to blow out into the ambient air. The highest N concentrations for 0.5% and 2% of N2 in the feed gas were 1.3 ⋅ 10 15 cm−3 and 4 ⋅ 10 15 cm−3, respectively. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background and Objectives: Fractional ablative resurfacing techniques are preferred treatments for facial rejuvenation of aged skin. This study was performed to investigate the cutaneous effects of using a fractional picosecond laser at 1064 nm with a diffractive lens. Methods: The penetration depth according to the location of the handpiece tip was evaluated using an acrylic panel. Laser induced optical breakdown (LIOB) and cutaneous damage were observed after hematoxylin and eosin staining in guinea pigs. Collagen formation was evaluated using Victoria staining, Masson's trichrome (MT) staining, and immunohistochemical staining for collagen type III. Results: The penetration depth for LEVEL 1 was 499.98–935.23 μm (average: 668.75 ± 182.84 μm); the LIOB cavity area was 1664.17 ± 650.52 μm2. The penetration depth of LEVEL 2 was 257.12–287.38 μm (average: 269.77 ± 14.55 μm) with an LIOB cavity area of 1335.85 ± 214.41 μm2. At LEVEL 3, that was 36.17–53.69 μm (average: 52.15 ± 20.81 μm) and the LIOB cavity area was 1312.67 ± 1069.12 μm2. No epidermal tissue damage was observed and collagen formation was observed from day 14 under all conditions. Conclusion: Diffractive optical element (DOE) lens arranged laser treatment system controlled the position of LIOB occurrence and an irradiating area. [ABSTRACT FROM AUTHOR]

Background: Differences in clinical efficacy based on the fluence of fractional picosecond laser treatment for acne scars are unknown. Objective: To compare the efficacy and safety of low‐fluence versus high‐fluence fractional picosecond Nd:YAG 1064‐nm laser treatment in acne scar patients. Methods: In this 12‐week, investigator‐blinded, randomized, split‐face study, 25 patients with moderate‐to‐severe acne scars received three sessions of high‐fluence laser treatment (1.0 J/cm2) on one side of their face and low‐fluence (0.3 J/cm2) on the other side every 4 weeks. Patients were assessed using acne scar counts, the scar global assessment (SGA), and the ECCA scar grading scale every 4 weeks. The histological analysis compared the acne scars obtained before and 4 weeks after treatment. Results: At their last visit, 88.00% and 92.00% of the subjects achieved >30% reduction in scar counts on the low‐ and high‐fluence sides, respectively, without a significant difference between the two sides. On both sides, the scar counts, SGA, and ECCA score significantly improved 4 weeks after the last treatment. Although the high‐fluence side showed a greater reduction in scar counts (−66.73%) than the low‐fluence side (−62.13%), the two sides had no significant difference in the grading scores. The high‐fluence side showed significantly more severe pain and higher side‐effect scores immediately and 4 weeks after treatment. Histological analysis revealed a significantly increased collagen, elastin, and vimentin expression after treatment on the low‐fluence side. Conclusions: The low‐fluence setting demonstrated comparable efficacy and superior safety in treating acne scars compared with the high‐fluence setting. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Q-switched lasers have undeniably revolutionized the field of laser dermatology since four decades ago. Just as the first-generation laser emits its photonic signal in a few nanoseconds, the picosecond laser delivers pulse widths of at least ten times shorter. These devices offer a powerful tool for treating a wide range of skin conditions with a minimal downtime for visible improvement. For the current study, a literature research was performed on the dermatological applications of picosecond laser. The literature searched on this topic between 1999 and 2023 accessible through various platforms produce a result of 62 articles. The included studies have discussed the application of picosecond laser technology in tattoo removal, treatment of epidermal and dermal pigmentation, and collagen remodeling. After sifting the data from the articles into tables, the results were discussed in detail. The study shows a lot of evidence towards the efficacy of picosecond laser, yet it draws attention to its downsides. [ABSTRACT FROM AUTHOR]

Background: Melasma results from the imbalance of the mechanisms that regulate skin pigmentation, causing the appearance of hyperpigmented patches. Treatment includes topical and oral agents, chemical peelings, microneedling, and laser therapy. The picosecond laser was developed to minimize pain and skin discoloration, which can sometimes be associated with laser treatments. It emits short pulses of energy that last from 300 to 500 picoseconds, leading to a more significant fragmentation of melanin, with miniminal risk of scarring and thermal lesions in the surrounding skin. Objective: The authors aimed to review the use of picosecond laser in the treatment of melasma and further provide an overview of the other current available options. Conclusions: While the use of picosecond laser for the treatment of melasma has yielded good results, further studies with longer follow-up periods and a higher number of patients are needed. [ABSTRACT FROM AUTHOR]

One challenge in the development of new drug formulations is overcoming their low solubility in relevant aqueous media. Reducing the particle size of drug powders to a few hundred nanometers is a well‐known method that leads to an increase in solubility due to an elevated total surface area. However, state‐of‐the‐art comminution techniques like cryo‐milling suffer from degradation and contamination of the drugs, particularly when sub‐micrometer diameters are aspired that require long processing times. In this work, picosecond‐pulsed laser fragmentation in liquids (LFL) of dispersed drug particles in a liquid‐jet passage reactor is used as a wear‐free comminution technique using the hydrophobic oral model drugs naproxen, prednisolone, ketoconazole, and megestrol acetate. Particle size and morphology of the drug particles are characterized using scanning electron microscopy (SEM) and changes in particle size distributions upon irradiation are quantified using an analytical centrifuge. The findings highlight the superior fragmentation efficiency of the liquid‐jet passage reactor setup, with a 100 times higher fraction of submicrometer particles (SMP) of the drugs compared to the batch control, which enhances solubility and goes along with minimal chemical degradation (<1%), determined by attenuated total reflection‐Fourier transform infrared spectroscopy (ATR‐FTIR), high‐performance liquid chromatography (HPLC), and X‐ray diffraction (XRD). Moreover, the underlying predominantly photo‐mechanically induced laser fragmentation mechanisms of organic microparticles (MP) are discussed. [ABSTRACT FROM AUTHOR]

Background/purpose: Riehl's melanosis is a difficult‐to‐treat condition characterized by persisting dermal hyperpigmentation. This study aimed to evaluate the efficacy of a histology‐specific targeted therapy for Riehl's melanosis. Methods: Skin biopsy samples of Riehl's melanosis were assessed to identify histology‐specific targets for treatment. Subsequently, the efficacy of a combination involving a fractional picosecond laser and a pulsed dye laser (PDL) targeting the dermal melanin and vessels, respectively, was evaluated. Clinical improvement was assessed using the dermal pigmentation area and severity index (DPASI). The treatment outcomes were compared to those of a control, in this case a single laser treatment solely targeting pigmentation. Results: Histological and immunohistochemical analyses identified dermal melanin pigment and dilated vessels as treatment targets for Riehl's melanosis. The combined treatment of the fractional picosecond laser and PDL showed a significant reduction of the DPASI scores, which was significantly better than the control group. Patients who underwent the combined laser treatment indicated high levels of satisfaction with no adverse events except of transient erythema and oedema. Conclusion: The combined treatment of a fractional picosecond laser and a PDL was more effective for Riehl's melanosis compared to single laser treatment. The treatment targets both dermal pigmentation and dilated vessels, offering promising results for those working to manage Riehl's melanosis. [ABSTRACT FROM AUTHOR]

In this work, direct laser ablation (DLA), liquid-assisted laser ablation in water (LALA-W) and in ethanol (LALA-E) is applied to fabricate single micro-channels on the zirconia ceramic by using a picosecond laser. To assess the machining ability of them, micro-channels fabricated are characterized and compared the differences in morphology, geometric profile, chemical and phase composition. The morphological results indicate that both LALA-E and DLA can fabricate microchannel with obvious recast layer and cracks, and LALA-W can fabricate microchannel with a porous surface, and almost no recast layer and cracks. The results of geometric characteristics show that LALA-W can fabricated micro-channels with "U" shape profile with 52.74% enhancement in depth compared to that "V" shape by DLA and LALA-E. The XPS results demonstrate that LALA-W can exhibit the smallest oxygen vacancies with 50.01% than that of LDA 53.81% and LALA-E 54.56%. For XRD results, after machining by all three processes, the zirconia ceramic undergoes the tetragonal→monoclinic phase transformation, resulting in an increase in monoclinic phase. While LALA-W exhibits the smallest increase in monoclinic phase from 9.9% to 12.7%, and has the most tetragonal phase content of 58.8%. [ABSTRACT FROM AUTHOR]

Regulating cell growth, extracellular matrix deposition and mineralization of artificial implants are some important parameters that decide the longevity of implants in the body. Picosecond laser‐induced hybrid groove structures have been shown to improve these properties of the Ti‐6Al‐4V bio‐alloy. Two hybrid structures containing groove patterns with periodic and non‐periodic substructures therein were generated on Ti‐6Al‐4V by varying the extent of laser pulse overlapping on sample surface. Laser‐induced alteration in surface topography, chemical composition and wettability of Ti‐6Al‐4V resulted in 3‐fold increase in the rate of hydroxyapatite growth, 2.5‐fold increment in protein adsorption and 2‐fold enhancement in cell adhesion in comparison to pristine sample. While the periodic substructure was found to guide cell growth, the nonperiodic sub structure offered homogenous growth leading to higher overall cell density on the substrate surface. [ABSTRACT FROM AUTHOR]

PurposeThis work demonstrates significant advantages in ophthalmic surgeries through the use of picosecond ultrashort laser pulses instead of state-of-the-art nanosecond laser pulses. These ultrashort lasers shall serve as universal tools more effectively combining advantages of high precision, low impact and economic advantages compared to existing instruments.MethodsAs samples, we used post-mortem porcine eyes on which we performed the experiments with both picosecond and nanosecond lasers. Performed surgeries were laser iridotomy, (post-) cataract treatment/capsulotomy and selective laser-trabeculoplasty. Pulse widths were between 12 ps and 220 ns with pulse energies between 30 μJ and 10 mJ at 532 nm and 1,064 nm. Additionally, we investigated accompanying shock waves, cavitation bubbles, and heat effects during the ablation processes.ResultsFor all surgeries, significant differences were observed between picosecond and nanosecond pulses: It was possible to scale the pulse energy down to 10 of microjoules rather than requiring millijoules, and resulting tissue ablations are much more precise, more deterministic and less frayed. The shock wave and cavitation bubble investigation revealed major differences in pressure between picosecond pulses (0.25 MPa, 50 μJ) and nanosecond pulses (37 MPa, 5 mJ). The heat input during ablation could be lowered by two orders of magnitude.ConclusionPicosecond ultrashort laser pulses show substantial benefits for several ophthalmic surgeries, with regard to ablation precision, shock wave generation and heat input. They are better than state-of-the-art ophthalmic nanosecond lasers in all aspects tested.

We present an effective approach to realize a highly efficient, high-power and chirped pulse amplification-free ultrafast ytterbium-doped yttrium aluminum garnet thin-disk regenerative amplifier pumped by a zero-phonon line 969 nm laser diode. The amplifier delivers an output power exceeding 154 W at a pulse repetition rate of 1 MHz with custom-designed 48 pump passes. The exceptional thermal management on the thin disk through high-quality bonding, efficient heat dissipation and a fully locked spectrum collectively contributes to achieving a remarkable optical-to-optical efficiency of 61% and a near-diffraction-limit beam quality with an M2 factor of 1.06. To the best of our knowledge, this represents the highest conversion efficiency reported in ultrafast thin-disk regenerative amplifiers. Furthermore, the amplifier operates at room temperature and exhibits exceptional stability, with root mean square stability of less than 0.33%. This study significantly represents advances in the field of laser amplification systems, particularly in terms of efficiency and average power. This advantageous combination of high efficiency and diffraction limitation positions the thin-disk regenerative amplifier as a promising solution for a wide range of scientific and industrial applications.

This current retrospective study, including 98 patients aged 21 to 71 years, aims to assess the safety and the efficiency of a picosecond 755 nm/532 nm laser in the removal of complex eyebrows tattoos. Patients were treated with a picosecond laser at 755 nm with fluences ranging from 0.69 to 6.37 J/cm2 and at 532 nm with a fluence of 0.64 or 1.12 J/cm2. Analyses of Variance (ANOVA, single factor) and comparison tests (F-test) were conducted. A total of 70 subjects finished the full treatment. An average of three laser sessions were necessary to achieve the patients’ objective (total removal, attenuation for redo, or correction). The number of sessions was significantly higher if cosmetic tattoos contained visible warm pigments (red, orange, yellow). A total of 18 patients experienced immediate grey discoloration, although this was not found to significantly influence the number of laser sessions. The main side effects were redness, swelling, and bleeding points. One patient experienced a bruise immediately after laser shots. This retrospective study has shown the picosecond laser to be safe and efficient in removing complex cosmetic tattoos. Further investigation is ongoing to assess optimal parameters for treating red and white pigments.

Objective To study the effect and safety of 532 nm picosecond laser in the treatment of freckles. Methods From November 2021 to March 2023, 104 patients with facial freckles were recruited in this retrospective clinical study. According to age and skin Fitzpatrick classification, it was divided into group A (21 to 30 years old), group B (31 to 40 years old), group C (41 to 50 years old), and group D (51 to 60 years old). All patients were grouped by age and Fitzpatrick skin classification and treated with a 532 nm picosecond laser once. All patients were assessed for clinical efficacy, and adverse reactions after 1 to 3 months. Results After one treatment, the overall effective rate was 94.23%, the cure rate was 45.19%, and there was no obvious correlation with between age and Fitzpatrick skin classification. The post-inflammatory hyperpigmentation occurred in 6 patients. Temporary hyperpigmentation alleviated 3 to 6 months after the treatment. Conclusion The 532 nm picosecond laser is a safe and effective modality for removing freckles without scarring or permanent pigmentary changes. [ABSTRACT FROM AUTHOR]

BackgroundThe 1064-nm Nd:YAG picosecond lasers using fractional micro-lens array (P-MLA) was a promising therapy for skin resurfacing. However, no studies have compared P-MLA with ablative fractional 2940-nm Er:YAG lasers (AF-Er) in the treatment of atrophic acne scars.ObjectivesTo evaluate the efficacy and safety of P-MLA and AF-Er for the treatment of atrophic acne scars.MethodsWe performed a prospective, randomized, split-face, controlled pilot study. Thirty-one Asian patients with mild to moderate atrophic acne scars underwent four consecutive sessions of randomized split-face treatment with P-MLA and AF-Fr at 4-week intervals. The efficacy of the two devices were evaluated by Echelle d’Evaluation Clinique des Cicatrices d’acne (ECCA) grading scale, Investigator’s Global Assessment (IGA) score and patient’s satisfaction. VISIA analysis was also performed to evaluate the pore and skin texture. Adverse events were recorded at each follow-up.ResultsThe P-MLA afforded comparable clinical responses in scar appearance as AF-Er based on the investigator’s assessments (ECCA percent reduction: 39.11% vs. 43.73%; IGA score: 2.97 ± 0.65 vs. 3.16 ± 0.68; P > 0.05 for both). However, the result of patient satisfaction indicated the AF-Er-treated side achieved a slightly greater improvement in scar appearance (3.97 ± 0.78 vs. 3.55 ± 0.71; P < 0.05). Overall, the two devices did not differ largely in terms of efficacy. VISIA analysis revealed similar changing patterns of the pore and skin texture between two devices. For safety profiles, no serious side effects were reported on both sides. The P-MLA showed lower pain level, shortened duration of crust shed and edema, and less occurrence of PIH (P < 0.05 for all).ConclusionCompared with AF-Er, P-MLA afforded comparable effect and more safety profiles in treating atrophic acne scars in Asian patients.Clinical trial registrationClinicalTrials.gov, identifier NCT 05686603.

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Photoacoustic (PA) theranostics is a new emerging field that uniquely combines diagnosis and treatment in one modality. However, its current status is compromised by the indispensable dependence on nonreversible phase-change nanoprobes that provides one-time-only action. Here, we demonstrate a picosecond-laser-pumped ultrafast PA cavitation technique for highly efficient shockwave theranostics, guaranteeing sustained PA cavitation by using non-phase-change nanoprobes. Theoretical simulations validate that, when compressing the excitation laser pulse width to hundred-picosecond, the thermal confinement effects of a conventional nanoprobe will induce transient heating of the extremely thin surrounding liquid layer of the nanoprobes beyond its cavitation point in a localized area at nanoscale, resulting in intense cavitation and PA shockwaves by the environment rather than the nanoprobes. Both cellular and mouse model experiments have demonstrated the highly effective anti-tumor effects. This method provides a sustainable, reproducible, and highly effective strategy for PA theranostics, prefiguring great potential for the clinical applications.

Fiber-reinforced concrete (FRC) is a cementitious composite material that is gaining interest in the construction field to limit crack propagation and increase toughness. Polypropylene (PP) fibers are promising alternatives to steel fibers, primarily used in FRC, as they reduce weight and cost and are resistant to corrosion. However, the hydrophobic surface of PP inhibits a good adhesion with the surrounding cementitious matrix and so the exploitation of optimized mechanical performance. Though several chemical treatments have been studied, this work suggests more sustainable, cost-efficient, and fast surface treatments for the first time to increase the hydrophilicity of PP: UV-LED, picosecond UV-LASER, and corona discharge treatment. The treatments mainly provided a chemical functionalization without altering the surface morphology of PP, and their effectiveness in increasing PP hydrophilicity was confirmed by ATR-FTIR spectroscopy and optical contact angle measurements. The improved adhesion with the matrix was assessed by the pullout test of treated PP specimens from lime-based and cement-based matrices and by detecting the failure mode in the interphase zone through scanning electron microscopy. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

ABSTRACTIn 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.

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.

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department 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 Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic 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 paper we present three technical improvements that will better prepare satellites for their later removal prior to launch, in accordance with international agreements such as the IADC Space Debris Mitigation Guidelines, which ensure that satellites are designed to re-enter within 25 years. Space debris are non- functional satellites orbiting the Earth, such as abandoned second stage rockets, nanosatellites (most of which have no onboard propulsion) and collision fragments including those from deliberate destruction. Just-in-time Collision Avoidance (JCA) can prevent anticipated collisions. It requires far more precise orbit parameters for debris than we have now. The main tool we will use is ultra-precise laser ranging from an orbiting ranging station, which can operate up to 500 km range from a debris, provided it has good optical cross-sections. To enhance cross-sections, we would install 1-cm optical corner reflectors on each satellite, four around its equator and two at its poles so that one or more will always be visible. We compare pulsed and frequency-chirped CW lasers in this regard. To better optimize energetic efficiency of laser propulsion to nudge satellites away from a predicted collision, we suggest the Thomson scattering technique, which permits simultaneously measuring the change of target velocity and the plume exhaust velocity, which can be combined to calculate this efficiency in real time.

Silicon carbide (SiC) ceramic is becoming widely used in multiple industrial applications, owing to its exceptional high-temperature properties. Yet it is still a challenge to machine SiC using traditional means without causing damage due to its high hardness and brittleness. In this study, a subtractive manufacturing technique based on the use of a fiber picosecond laser was employed to remove material from the reaction bonded SiC surface or create micro-patterns with the minimum damage to the surface, maximum surface quality and precision. Multiple laser processing parameters were investigated with the purpose of obtaining deep high-quality cuts with the minimum surface roughness and the minimum amount of the re-deposited material. The heat affected zone was analyzed by grazing angle X-ray diffractometry, cross-sectional scanning electron microscopy, energy dispersive and micro Raman spectroscopy techniques. The cut shape, depth, surface roughness as well as the kerf width and re-deposition height were assessed using a 3D laser scanning microscopy. The optimum values were established for the focal position, the laser power, linear speed, wobble frequency, wobble pattern, and number of passes. This study also identified the processing parameters for shallow and deep high-precision SiC cutting at a material removal rate of ∼2 mm3/min. The work demonstrated that the developed laser machining process is an efficient subtractive manufacturing tool that can be integrated into the automated precision cutting systems for machining hard ceramic materials such as SiC and alumina. [ABSTRACT FROM AUTHOR]

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]

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]