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Abstract Space debris laser ranging with a 4.2 W double-pulse 532 nm picosecond laser at a pulse repetition frequency of 1 kHz was achieved at the Shanghai satellite laser ranging (SLR) station, which receiving telescope was 60 cm. Space debris' radar cross sections were from 2 m2 to 12 m2, and ranging precision was up to centimeters. A compound regenerative amplifier was used to realize double pulses output with pulse space of 4.1 ns. Double pulses would have the same detection ability as the equal energy single pulse. A 500 μm diameter avalanche photo-diode detector with less than 10 kHz dark noise and a quantum efficiency of 40% at 532 nm was developed to improve the measurement capability. And also a spectral filter with high efficiency and narrow bandwidth were applied. Basing on the Shanghai SLR system, the laser ranging to space debris with picosecond laser at 1 kHz was successfully implemented for the first time among the global SLR stations. The results showed that the ranging precision root-mean-square can be achieved about 5 cm. It will be very useful to monitor and study the space debris. [ABSTRACT FROM AUTHOR]

The laser processability of dental prosthesis is investigated using two ceramic composites, including 3M, Lava Ultimate and Ivoclar vivadent, IPS e.max. Materials and methods: The CO2 laser, picosecond laser and femtosecond laser are used to assess the processing power of dental prosthetic materials Lava Ultimate and IPS e.max and the line processing shape was measured using a confocal microscope. Results: The brittleness, carbonization and micro crack of the ceramic composite were influenced by heat accumulation of the material and could be controlled by the laser power and pulse time. Conclusion: In the case of CO2 lasers, micro crack and carbonation occurred immediately, and in the picosecond laser processing, the micro cracks are partially improved, but the carbonization occurs continuously. Finally, we confirmed the high efficiency of laser processing with femtosecond laser. In particular, Lava Ultimate, a ceramic resin composite material, showed the best processability when processed using a femtosecond laser. [ABSTRACT FROM AUTHOR]

Abstract A high-power 808 nm diode-directly-pumped passively mode-locked 1064nm Nd:YVO 4 laser was demonstrated with a semiconductor saturable absorber mirror (SESAM). Through theory analysis and carefully experimental optimization of laser mode radii in the laser crystal and on the SESAM. An average output power of 3.39 W and single pulse energy of 0.115 μJ was obtained with a pulse width of 16.3ps and a repetition rate of 29.36 MHz under a pump power of 8.92 W, corresponding to an optic-optic efficiency of 38.0％ and the high beam quality in the x, y direction was 1.12 and 1.07, respectively. [ABSTRACT FROM AUTHOR]

Picosecond laser pulses, in laser polishing, induce a light-material interaction in an extremely short period of time to melt steel. The generated heat affected zones (HAZ) are almost negligible. The induced thermal distortion of the polished workpieces can be reduced notably. This paper shows a kind of powder-metallurgical steel, ASP23, polished by a picosecond laser. The purpose of this research is to reduce thermal distortion of the workpieces after laser polishing. The surface morphologies and roughness of the polished surfaces are shown as well. Fourier analysis is used to analyze the surfaces of polished materials. In addition, the microstructure of polished ASP23 surfaces is examined. [ABSTRACT FROM AUTHOR]

The novel picosecond lasers, initially developed for faster tattoo removal, have also shown great efficacy in endogenous pigmentary disorders. To describe the efficacy and safety profile of an alexandrite (755-nm) picosecond laser in a wide range of pigmented flat and elevated cutaneous lesions. A retrospective study was performed in which we collected all the clinical images of patients treated with the 755-nm alexandrite picosecond laser for 12 months (November 2016-November 2017). Clinical features were obtained from their medical charts. Patients treated for tattoo removal were excluded. All the images were analyzed by three blind physicians attending to a visual analogue scale (VAS) from 0 to 5 (0, no change; 1, 1-24% clearance; 2, 25-49% clearance; 3, 50-74% clearance; 4, 75-99% clearance; 5, complete clearance). Patient satisfaction was obtained from a subjective survey including four items: very satisfied, satisfied, non-satisfied, and totally dissatisfied. Thirty-seven patients were included (12 males; 25 females). The mean age of the study was 42.35 years. Twenty-five patients (68%) were treated for different pigmented flat disorders such as solar and mucosal lentigines (5), stasis dermatitis (4), or nevus of Ota (4), among other diagnoses. Twelve patients (32%) were treated for epidermal elevated lesions such as warts (5), epidermal nevi (2), and seborrheic keratosis (3), among other elevated lesions. Mean number of laser treatment was 3.02 sessions while mean follow-up after last laser treatment was 4.02 months. Mean VAS score of the three observers was 3.44 (61% of clearance) for pigmentary flat disorders and 3.60 (67%) for elevated lesions. Adverse effects reported were mild blistering in the first 2-5 days following laser treatment in some of the patients. Overall satisfaction among the patients included was high. The novel 755-nm picosecond alexandrite laser is effective not only for the resolution of pigmented flat lesions of different nature but also for the treatment of the more difficult elevated pigmented lesions. [ABSTRACT FROM AUTHOR]

An average power of 3 W green picosecond laser at a pulse repetition frequency of 1 kHz was reported. At the Shanghai satellite laser ranging (SLR) station, many satellites were measured with this laser and a narrow spectrum filter in the daytime. Satellites of the Beidou satellite navigation system for the Chinese, Global navigation satellite system for the Russian and Galileo satellite navigation system for the Europe were measured respectively. Especially ranging precision root mean square was up to 19.4 mm for the satellite of compassi5 about 37,000 km far from the earth. A Nd:YVO 4 mode-locked laser with an etalon, a dual-length of Nd:YAG regenerative amplification cavity, single-pass two Nd:YAG modules amplifier and nonlinear optical materials LiB 3 O 5 frequency doubling were designed. An average power of 3 W in 532 nm was obtained with pulse width of 30 ps, and angle of divergence was 0.8 mrad. Using the dual-length of regenerative cavity would greatly decrease the laser's volume and improve stability of picosecond laser. A narrow spectrum filter can reduce a lot of optics noise from the sun, and so all the satellites were almost be measured with this laser in the daytime at the Shanghai SLR station. [ABSTRACT FROM AUTHOR]

Phase-change materials (PCMs) have been widely used in optical and electronic applications for their extraordinary properties. However, the procedure of fast transition about PCMs is still not clear for the time limit. Pulse laser, especially ultra-short pulse laser, is an excellent tool to study the crystallization characteristics of PCMs for its high heating rate. In this paper, picosecond pulsed laser was employed to study the crystallization of amorphous Ge 2 Sb 2 Te 5 (a-GST) thin films via the evolution of morphology and microstructure. The threshold for inducing crystallization was 7.9 mJ/cm 2 and amorphization occured at 17.2 mJ/cm 2 . With the aid of high-resolution transmission electron microscopy (HRTEM), the growth of grains were observed to own a preferable growth direction of [100]. The grain size and laser fluence showed an exponential relationship under the ps laser pulse, and the maximal grain reached to ~5 μm when approaching the melting point. The morphology and grain distribution of GST film under 18.8 mJ/cm 2 indicated a solid-state phase transition. Besides, the matrix of a-GST film changed into crystalline state even though the surface melted into amorphous state when irradiated by high laser pulse. Finally, the reason for fast transition of a-GST film under ultra-short laser pulse was discussed in terms of heating rate and temperature. The present study is fundamental for the understanding of the fast phase transition of PCMs. [ABSTRACT FROM AUTHOR]

Ultrafast laser-induced surface modification of materials has attracted significant attention in recent years. The mechanism of formation of ultrafast laser-induced periodic surface structures (LIPSS), which were evenly distributed over the large area of indium tin oxide, was studied both theoretically and experimentally. Films were deposited using 10-ps 1064-nm laser. Resistance and transmission characteristics of LIPSSs on ITO film were analyzed. The resistance of LIPSSs increases with the increasing of transmittance in infrared band within a certain range. The paper reports the optimal processing parameters for the realization of LIPSSs on ITO films established based on the resistance and transmission properties of the film. The film with the optimized structure can significantly improve the infrared transmittance function of ITO while ensuring the low resistance, which can greatly improve the power generation efficiency of the thin film solar cells. [ABSTRACT FROM AUTHOR]

Abstract Bio-ceramics typified by hydroxyapatite (HAP) are drawing more and more attention due to their unique properties including bioactivity, biocompatibility and proper mechanical hardness and strength. However, the machinability of HAP by using conventional methods is poor. An exploration of micro-grooving of HAP employing ultrashort pulsed laser is carried out in this study, and orthogonal experimental method is used with various factors considered including laser scanning times, high voltage level, pulse frequency, scanning velocity and focal plane position. Range analysis is conducted and the significance of selected factor on the groove profile is discussed. It has been found that microgrooves of width and depth varying between 20∼45 μm without obvious thermal damage can be achieved when the parameters are properly selected, demonstrating the feasibility of the ultrashort picosecond laser in micro-processing of HAP. Meanwhile, cracks, recast layer and edge fracture occur in few cases, suggesting that the material removal mechanism in this process is not purely phase explosion as for femtosecond laser. The energy dispersive spectroscopy (EDS) comparison results between ablated and non-ablated surfaces illustrate an obvious change in the composition ratio of element oxygen (O), indicating that there may exist chemical reaction at the laser irradiation zone. Based on the analyses on groove profile and thermal damage, recommendations are made on processing parameters selection for micro-grooving of HAP. Highlights • The experimental study demonstrates the feasibility of the ultrashort picosecond laser in micro-processing of brittle HAP. • Laser scanning times and HV level are the two factors affecting the groove profile most significantly. • The thermal damages occur more easily when repeating the laser scanning process under high HV level. • Depending on the machining parameters, different material removal mechanisms may occur in this micro-grooving of HAP. [ABSTRACT FROM AUTHOR]

Low dimensional accuracy and high surface roughness induced by the inherent powder adhesion and staircase effect are the critical challenges for the application of parts fabricated by laser powder bed fusion (LPBF). In this study, an innovative hybrid additive manufacturing process by adding the ultrafast laser machining to the LPBF process was proposed. After LPBF process, the additively manufactured samples were micromachined using a picosecond laser. The effects of parameters (i.e. , laser frequency, and scanning speed) of the ultrafast laser machining on the surface morphology were investigated by the single-pass ablation experiments. The impact of the scan counts on the cutting depth was analyzed by the large-area cutting experiments. Subsequently, samples with different tilt angles were fabricated by a hybrid additive manufacturing process with alternating processing of LPBF and the ultrafast laser machining. The side surface roughness (4.98 ± 0.44 µm) of the samples fabricated by hybrid additive manufacturing process was lower than that of as-built LPBF samples. The processing characteristics and the ablation morphology of the picosecond laser were investigated. The factors affecting the quality of hybrid manufacturing were systematically discussed. This work may provide a new way to manufacture parts with high dimensional accuracy and low surface roughness by LPBF. • A new hybrid additive manufacturing combining LPBF and picosecond laser processing was realized. • The picosecond laser processing characteristics and process parameters of AM stainless steel samples were investigated. • The side surface roughness was reduced by the hybrid additive manufacturing process. • The main factors affecting the surface quality in hybrid additive manufacturing process were discussed. [ABSTRACT FROM AUTHOR]

Due to its high hardness and excellent wear resistance, single crystal diamond has been widely applied in mechanical processing. However, the outstanding hardness leads to great difficulties in the machining of diamond by traditional strategies. In this study, a synchronous feed laser method is developed to realize low damage, high efficiency, and high precision machining of single crystal diamond cutting tools. The disadvantages of traditional direct laser machining, including fullerene residue, bending behavior, and the plasma-shield effect, are well avoided by the good control of the scanning path during the laser fabrication, which enlarges the entrance of the kerf and reduces the air pressure inside the kerf. The synchronous feed laser machining can realize the remarkable increase of kerf depth at high speed, as well as a minimum roughness of ∼147 nm on the cutting surface. It provides a novel, high efficiency, and high precision strategy for the preparation of high quality single crystal diamond tools. [Display omitted] • Proposing a synchronous feed strategy for high quality diamond tool fabrication. • Discussing and solving the issues of bending behavior and fullerene residue. • Achieving a high efficiency and low surface roughness diamond cutting. [ABSTRACT FROM AUTHOR]

• 4H-SiC samples were stealthy diced along [ 11 2 ¯ 0 ] and [ 1 1 ¯ 00 ] orientations by infrared picosecond laser and then three-point bending split. • The critical fracture load of 4H-SiC along [ 11 2 ¯ 0 ] orientation is smaller than that along [ 1 1 ¯ 00 ] orientation. • The laser ablation points have larger longitudinal length along [11 2 ¯ 0] orientation compared with [1 1 ¯ 00] orientation. • 4H-SiC samples diced along [ 11 2 ¯ 0 ] orientation has smaller chipping width and section roughness than [ 1 1 ¯ 00 ] orientation. Stealth dicing of semi-insulating 4H-SiC along [ 11 2 ¯ 0 ] and [ 1 1 ¯ 00 ] crystal orientations on Si-face and C-face was conducted by using infrared picosecond laser in combination with three-point bending split. It was demonstrated that the laser ablation points inside 4H-SiC samples, the critical fracture load, and the dicing quality of 4H-SiC samples were closely related to the crystal orientation. The critical fracture load of 4H-SiC along [ 11 2 ¯ 0 ] orientation is smaller than that along [ 1 1 ¯ 00 ] orientation. The longitudinal lengths of the laser ablation points increase with the increase of laser incident distance. For the same laser-modified layer, as laser was incident from C-face and processed along [ 11 2 ¯ 0 ] orientation, the laser ablation points have larger longitudinal length. The reasons for the impact of crystal orientation on laser-modified points were analyzed. The fractured 4H-SiC samples have chipping width less than 3 μm and section roughness less than 500 nm. Moreover, the dicing quality along [ 11 2 ¯ 0 ] orientation is better than that along [ 1 1 ¯ 00 ] orientation. This research can provide technical support for precision dicing of SiC wafers in semiconductor industry. [ABSTRACT FROM AUTHOR]

We present our research on the high energy picosecond laser operating at a repetition rate of 1 kHz and the high average power picosecond laser running at 100 kHz based on bulk Nd-doped crystals. With diode-pumped solid state (DPSS) hybrid amplifiers consisting of a picosecond oscillator, a regenerative amplifier, end-pumped single-pass amplifiers, and a side-pumped amplifier, an output energy of 64.8 mJ at a repetition rate of 1 kHz was achieved. An average power of 37.5 W at a repetition rate of 100 kHz pumped by continuous wave laser diodes was obtained. Compact, stable and high power DPSS laser amplifier systems with good beam qualities are excellent picosecond sources for high power optical parametric chirped pulse amplification (OPCPA) and high-efficiency laser processing.

We experimented with two polymer materials with different ultraviolet (UV) wavelength absorption characteristics, which are commonly used in flexible devices, by applying an ultrashort-pulsed laser of a 355-nm UV wavelength for 10 ps. The laser parameters studied were pulse repetition rate, laser irradiation method, and laser power condition. Previous studies using polyethylene terephthalate (PET), which does not exhibit linear absorption at a UV wavelength, have focused on processing trends resulting in minimal collateral damage around the laser-induced ablation. However, our results showed a trend of accumulating such damage irrespective of the laser parameters. Meanwhile, polyimide (PI) exhibited a completely different behavior depending on the laser parameters. At low pulse repetition rates, minimal collateral damage was observed, whereas at high repetition rates, the morphology varied considerably. The electrical characteristics of the laser-processed materials were found to be correlated with the variations in morphology. In the case of PI, such variations in electrical resistance and morphology indicated that the material was carbonized. The findings of this study are expected to provide a useful reference when selecting parameters for the laser processing of similar polymer materials.

Ultrafast non-diffractive Bessel laser beams provide strong light confinement and show robust advantages for fabricating high-aspect-ratio nanoscale structures inside transparent materials. They take the form of nanoscale voids with typical diameters well below the wavelength and aspect ratio of more than 1000. Delivering 3D morphologies of such nanoscale voids is an important issue to evaluate the result for fabrication. However, the characterization of such laser-induced structures is a difficult task. Here, an accurate and time-saving tomography-like methodology is proposed and adopted for reconstructing the morphology of high-aspect-ratio nano-holes. The technique allows an accurate assertion of laser parameters and position on nano-structured features. The reconstructed configuration reveals that nanoholes morphologies have a close relationship with energy distribution in the focal region. It suggests that the configuration of micro-explosion can be controlled by laser energy deposition in the process of laser-matter interaction down to the nanoscale.

The graphene paper microsieves can be applied in the filtration of biological fluids or separation of solid particles from exploitation fluids. To produce graphene paper microsieves for specific applications, good control over fabrication should be achieved. In this study, a laser ablation method using a picosecond laser was applied to fabricate graphene paper microsieves. Holes in the microsieves were drilled using pulsed laser radiation with a pulse energy from 5 to 100 µJ, a duration of 60 ps, a wavelength of 355 nm, and a repetition rate of 1 kHz. The impact method was applied using 10 to 100 pulses to drill one hole. To produce holes of a proper diameter which could separate biological particles of a certain size (≥10 µm), optimum parameters of graphene paper laser ablation were defined using the MATLAB software taking into account laser pulse energy, repetition rate, and a desired hole diameter. A series of structural tests were carried out to determine the quality of an edge and a hole shape. Experimental results and Laguerre–Gauss calculations in MATLAB were then compared to perform the analysis of the distribution of diffraction fringes. Optimum experimental parameters were determined for which good susceptibility of the graphene paper to laser processing was observed.

Lithium niobate (LiNbO3) has become popular with applications in electronics and communication industries due to its excellent electro-optical and nonlinear properties. This paper presents the influence of laser power, repetition frequency, number of subpulses, depth of each pass, and scanning velocity in picosecond laser dicing on multiple characteristics of LiNbO3 using the Taguchi method. By means of analysis of variance and analysis of relations between the characteristics, the optimal ps-laser-dicing parameter is obtained with good quality and high efficiency, which is applied to LiNbO3 products. The result indicates that picosecond laser dicing provides an alternative to machine thick LiNbO3 wafers with narrow kerf width, micro chipping, smooth surface, and high productivity.

Dermoscopic appearances of the right (B) and left eyelashes (C). gl Nanosecond Q-switched lasers and picosecond lasers have been extensively used for the treatment of tattoo removal with excellent results and minor side effects. Nowadays, nanosecond Q-switched laser and picosecond laser treatments have been widely used for tattoo removal.[1] Although they are effective with relatively low risk of scarring, the side effects still exist. Keywords: adverse effect; leukotrichia; picosecond laser; tattoo removal; white eyelash EN adverse effect leukotrichia picosecond laser tattoo removal white eyelash 7228 7229 2 12/30/22 20221201 NES 221201 To the Editor, A lot of effort has been made for the elimination of unwanted tattoo such as chemical peeling, cryosurgery, surgical excision, or electro-cauterization. [Extracted from the article]

Longitudinal melanonychia (LM), also known as melanonychia striata, is characterized by one or more gray, brown, or black longitudinal streaks within the nail plate from the proximal nail fold to the distal part of the nail plate.[1] LM may be caused by nonmelanocytic or melanocytic origins. Permanent nail dystrophy, a potential concern for patients with LM receiving nail matrix biopsy, may be observed after different surgical techniques.[3] LM due to melanocytic activation can benefit from conservative approaches. For children and those who concerned postoperative nail dystrophy, picosecond laser may be an efficient alternative for nail pigmentation removal based on the selective photomechanical effect with minimal thermal damage to surrounding tissue. [Extracted from the article]

Hyperpigmentation of the gums can be associated to several etiological factors. Although it is physiological in most cases it can cause esthetic concerns in some patients. The objective of our study was to evaluate the clinical efficacy and patient satisfaction with the treatment of gingival hyperpigmentation with picosecond alexandrite laser of 755 nm. We selected two patients with gingival hyperpigmentation on the anterior face of the upper and lower gums of years of evolution. Malignancy, drug ingestion, exposure to tobacco and underlying genetic and endocrine alterations were ruled out. Clinical photographs were taken before treatment and 2 weeks after the procedure. In both cases, anterior gingival areas were depigmented with satisfaction. The patients did not complain of severe pain or discomfort. Two weeks after the procedure the gingiva showed almost complete depigmentation. In conclusion, the 755-nm alexandrite picosecond laser seems to be safe and effective for the esthetic treatment of gingival hyperpigmentation. [ABSTRACT FROM AUTHOR]

We report a stable optical fiber pumped Nd:YVO4 all solid state regenerative amplifier with all fiber picosecond laser as seed source. 888 nm Yb optical fiber lasers was chosen as pump source to reduce quantum defect for improved thermal performance. At the repetition rate of 99.6 kHz, maximum power of 19.63 W with 36 ps pulse duration were achieved when seeded by a 150 mW picosecond oscillator. The wavelength delivered was 1064.07 nm with spectral width of 0.14 nm.

We developed a confined microfluidic cell culture system with a bottom plate made of a microscopic slide with planar platinum sensors for the measurement of acidification, oxygen consumption, and cell adhesion. The slides were commercial slides with indium tin oxide (ITO) plating or were prepared from platinum sputtering (100 nm) onto a 10-nm titanium adhesion layer. Direct processing of the sensor structures (approximately three minutes per chip) by an ultrashort pulse laser facilitated the production of the prototypes. pH-sensitive areas were produced by the sputtering of 60-nm Si3N4 through a simple mask made from a circuit board material. The system body and polydimethylsiloxane (PDMS) molding forms for the microfluidic structures were manufactured by micromilling using a printed circuit board (PCB) milling machine for circuit boards. The microfluidic structure was finally imprinted in PDMS. Our approach avoided the use of photolithographic techniques and enabled fast and cost-efficient prototyping of the systems. Alternatively, the direct production of metallic, ceramic or polymeric molding tools was tested. The use of ultrashort pulse lasers improved the precision of the structures and avoided any contact of the final structures with toxic chemicals and possible adverse effects for the cell culture in lab-on-a-chip systems.

We report on a diode-pumped passively mode-locked picosecond Tm:CaGdAlO4 (Tm:CALGO) laser using a semiconductor saturable absorber mirror as the mode locker. With Tm:CALGO disordered crystal as gain medium, the mode-locked laser generated pulses with pulse duration of 27 ps, repetition rate of 128.6 MHz, and maximum average power of 330 mW at 1949.5 nm. To the best of our knowledge, this is the first demonstration of a mode-locked Tm:CALGO disordered crystal laser. The continuous-wave (CW) laser performance of Tm:CALGO was also investigated, and the maximum CW power was 730 mW. Our research results show that Tm:CALGO crystal is an excellent bulk medium for picosecond pulse generation at 2-μm wavelength.

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., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

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.

In the present study aluminium oxide (Al2O3) has been micro structured through laser milling process using a Nd:YVO4 picosecond laser. A statistical approach based on Design of Experiments (DoE) has been successfully adopted with aim to detect which and how the process parameters affect the process as well as to explain the effect of the process parameters on the material removal rate and surface quality. The analysed parameters were scanning speed (Ss), power and line distance (i.e. the distance of two consecutive scan lines). The response variables were material removal rate and surface roughness. The ANalysis Of VAriance (ANOVA) has been applied to the results analysis. In order to understand the influence of main parameters and their interactions on the response variables, a Central Composite Design (CCD) has been chosen and performed successfully. [ABSTRACT FROM AUTHOR]

Development of rapid processes combining the preparation of porous structures with the control of their properties has remained a challenge. This is particularly true for applications of graphitized hierarchically porous carbon nanosheets (GHPCNs) predominantly focus on fields of energy storage and conversion materials, electronics, sensors, separation and detection. Here we report a one-step approach to transform commercial bakelite into three-dimensional high electrical conductivity GHPCNs using the high-repetition picosecond infrared laser scribing in nitrogen atmosphere. The GHPCNs with mesopores and macropores can be rapidly induced on bakelite plate by the transient laser heating due to thermal accumulation effect. Studies reveal that the in-plane topological defects of the bakelite-based GHPCNs flakes contain pentagon-heptagon structures. The local controllable laser patterning technique enables porous structures and shapes to be controlled in highly GHPCNs films with variable properties. The methodology developed here have great potential to stimulate both research and industrial interest in the development of bakelite-derived GHPCNs electronic and energy storage micro-devices. [ABSTRACT FROM AUTHOR]

The results on picosecond laser micro-drilling, engraving, and surface texturing of tungsten carbide (WC) substrate are presented. A systematic study was conducted on the influence of various laser parameters on the characteristics of laser machined features. The machined features such as micro-holes, engraved structures, and surface textures were evaluated with an optical microscope, scanning electron microscope/energy dispersive x-ray spectrometer. Under the identified optimum laser parameters, high quality different sized holes, engraved structures, and two-scale (micro/nano) surface textures on WC substrates were produced. The developed process has potential to be applied in the manufacturing of WC substrate based components for precision engineering industry. [ABSTRACT FROM AUTHOR]

To satisfy the beam pointing and centering requirements of a sophisticated sampling beam path for petawatt picosecond diagnostic systems, a laser-beam alignment system is applied to this diagnostic platform. A mathematical model of a 4D linear matrix is applied to achieve rapid and accurate beam alignment. This alignment system can also switch quickly between two channels sampling beams without disturbing the beam’s pointing and centering. Experimental results indicate that the near-field centering accuracy is 0.3 mm and the far-field pointing accuracy is 0.16 mrad. With this alignment system, the picosecond diagnostic system can realize stable and reliable pulse width diagnostic between 1 and 10 ps, and obtains high dynamic range signal-to-noise ratio diagnostic results. [ABSTRACT FROM AUTHOR]