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Picosecond laser ablation and depth profile of Cu(In, Ga)Se2 thin film layer
摘要： Laser ablation based on picosecond laser was used to achieve the micro-analysis of Cu(In, Ga)Se2 (CIGS) thin film with the ablation crater diameter of 50 μm and the ablation crater central depth of 93 ± 13 nm. We achieved the depth profile of CIGS thin film with different laser shot number. The evolutions of spectral lines intensities of Ca from glass substrate and Ga and In from CIGS thin film layer, and intensity ratios of Ca/Ga and Ca/In could exhibit the change of the ablation volume, which could estimate the thin film thickness of single CIGS thin film layer. The average plasma temperature was calculated to be about 5243 ± 100 K, and the average electron density was calculated to be about 4.5×1016 cm?3. It is shown that our experimental setup is suitable to achieve a precise control and monitor the element compositions in each CIGS thin film layer in the research and in the production of CIGS solar cells.
关键词： Ablation morphology,Electron density,Cu(In, Ga)Se2 thin film,Picosecond laser induced breakdown spectroscopy,Plasma temperature
更新于2025-09-16 10:30:52
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Effect Analysis of Material Properties of Picosecond-Laser Nanoscale Ablation for Acrylonitrile Butadiene Styrene/PolyVinyl Chloride
摘要： ABS/PVC (Acrylonitrile Butadiene Styrene/PolyVinyl Chloride) is suitable for noncontact processing using laser as a tool. Laser-induced optical and thermal energy are utilized to decompose and ablate ABS/PVC. Optical and thermal properties of ABS/PVC play important roles on the laser-induced ablation depth. This paper proposed a model considering the energy balance and decomposition at the ablated interface due to the thermal transport, optical absorption and thermal activation energy in ABS/PVC. The ablation depth predicted by this study is validated by the experimental data. This paper verifies that the laser-pulse ablation rate at the initial processing time is dominated by optical penetration absorption for laser and is linearly proportional to the logarithm of the laser fluence by a ratio factor 'optical absorption length.' This study also analyse how the optical and thermal properties of ABS/PVC influence the variation of the laser-ablated depth with the laser fluences.
关键词： Picosecond Laser,Material Property,ABS/PVC
更新于2025-09-16 10:30:52
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Treatment of gingival pigmentation with a 755-nm alexandrite picosecond laser
摘要： 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.
关键词： Pigment laser,Alexandrite laser,Picosecond laser,Laser
更新于2025-09-12 10:27:22
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Evaluation of the Safety and Efficacy of a Picosecond Alexandrite Laser With DLA for Acne Scars in Chinese Patients
摘要： Background and Objectives: Recently, picosecond laser treatment has been used as an effective treatment for acne scars. To evaluate the efficacy and safety of a picosecond alexandrite laser with a diffractive lens array in the treatment of acne scars in Chinese patients. Study Design/Materials and Methods: Patients with facial acne scars were treated with a picosecond alexandrite laser in three sessions at 4‐ to 6‐week intervals and followed up for 2 months. Primary outcomes were measured by physicians’ blinded evaluation of the acne scar using the ECCA (échelle d’éva physicians’luation clinique des cicatrices d’acné) grading scale. The secondary outcomes included the investigator global assessment (IGA) on the improvement of post‐inflammatory erythema (PIE), patients’ assessment of improvement on a 4‐point scale and of satisfaction on a 5‐point scale. Pain scores and adverse effects were also evaluated. Result: Twenty patients with Fitzpatrick skin types III and IV were enrolled in the study and completed all treatment and follow‐up visits. The mean ECCA scores fell from 197.75 ± 35.26 to 142.00 ± 35.92 (a 28% improvement), and the change was significant (P = 0.000). The mean IGA score of PIE improvement was 3.03 ± 0.75 (0 = no improvement and 4 = 76–100% improvement). On the basis of the patients’ self‐assessment, the average improvement scores were 2.30 ± 0.98 (0 indicating 0–25% improvement and 3 indicating >75% improvement). In total, 50% and 30% of the patients were “satisfied” and “very satisfied,” respectively, with the treatment. The mean pain score was 3.20 ± 0.50 (0 = no pain, 10 = maximum pain) with topical anesthesia. The adverse effects included transient and mild erythema, edema, and scabbing. Conclusions: Treatment with a picosecond alexandrite laser with a diffractive lens array is effective and safe for acne scars in Chinese patients. Lasers Surg. Med. ? 2019 Wiley Periodicals, Inc.
关键词： picosecond laser,post‐inflammatory erythema,alexandrite laser,acne scars,fractional laser
更新于2025-09-12 10:27:22
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Thermal and optical performance characteristics of a spatial light modulator with high average power picosecond laser exposure applied to materials processing applications
摘要： A spatial light modulator (SLM) addressed with Computer Generated Holograms (CGH’s) can create structured light fields when an incident laser beam is diffracted by a phase CGH. The power handling limitations of SLMs based on a liquid crystal layer have always been of some concern. Now, with careful engineering of chip thermal management, we present the detailed optical phase and temperature response of a liquid cooled SLM exposed to picosecond laser average powers up to 220W at 1064nm – new knowledge critical for determining device performance at high laser powers. SLM chip temperature rose linearly with incident laser exposure, increasing by only 5°C at 220W incident power, measured with a thermal imaging camera. Thermal response time with continuous exposure was 1-2 seconds. The optical phase response with incident power approaches 2π radians with average powers up to 130W while above this power, liquid crystal thickness variations limit phase response to just over π radians. These remarkable performance characteristics show that liquid crystal based SLM technology is highly robust when efficiently cooled. High speed, multi-beam plasmonic surface micro-structuring at a coverage rate of 8cm2s-1 is achieved on polished metal surfaces at 25W exposure, while diffractive multi-beam surface ablation on stainless steel at an ablation rate of ～4mm3min-1 is demonstrated with average power 100W. Continuous exposure for many hours exceeding 100W laser power did not result in any detectable drop in diffraction efficiency hence no permanent changes in SLM phase response characteristics have been observed This research work will help to accelerate the use of liquid crystal SLMs for both scientific and ultra-high throughput laser-materials micro-structuring applications.
关键词： Spatial light modulator,active cooling,high average power picosecond laser,high power laser micro-machining
更新于2025-09-12 10:27:22
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Alopecia Totalis Treated with 1064 nm Picosecond Nd:YAG Laser: A Case Report
摘要： Alopecia areata (AA) is an autoimmune disorder causing nonscarring hair loss. Alopecia totalis (AT), the severe form of AA, is usually refractory to many ?rst-line treatments including topical and intralesional corticosteroids and topical immunotherapy. Systemic corticosteroids, ultraviolet light phototherapy, and immunosuppressants may be effective but can cause side effects and high recurrence rates after discontinuing treatment. Janus kinase inhibitors and numerous types of lasers, such as 308 nm excimer laser or light, low-level laser therapy, and fractional lasers have been explored for alternative treatment of AA over the past few years with bene?cial effects. Herein, we presented a case of AT treated with the novel 1064 nm picosecond Nd:YAG laser (ps-Nd:YAG) (Cutera, Brisbane, CA, USA) under a split-scalp study. A 25-year-old woman presenting with AT for two years was treated with topical and intralesional steroid and the 1064 nm Nd-YAG picosecond laser on the right half of the scalp. The laser treatment interval was once a month. The left half of the scalp was treated with topical and intralesional steroids alone. After treatment for six times, the right half of the scalp had greater improvement than the left half of the scalp. 1064 nm picosecond Nd:YAG laser therapy may be an effective alternative adjuvant treatment for AT.
关键词： alopecia,laser,alopecia areata,picosecond laser,alopecia totalis,hair loss
更新于2025-09-12 10:27:22
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1 kHz dual sub-pulse train picosecond radially polarized beam KGW Raman generator capable of achieving multiple optical communication wavelength
摘要： A dual sub-pulse train 1064 nm picosecond radially polarized beam pump KGW single-pass Raman generator was designed. The Stokes lines of both the 768 cm?1 and 901 cm?1 vibrational modes of the KGW Raman-active crystal were excited simultaneously. The Raman generator radiated up to seven Stokes lines in the infrared spectrum, which covered multiple optical communication channels. The overall Stokes average power reached 1.01 W, and the maximum Raman overall conversion efficiency was 23.1%. The interaction between the optical field and the Raman crystal was discussed from two perspectives of line width compression and beam quality.
关键词： Multi-wavelength KGW Raman laser,Nonlinear optics,Dual sub-pulse train picosecond laser,Infrared spectrum,Radially polarized beam
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Achievement of Very Smooth Cavity Sidewalls by UV Picosecond Laser Micromachining
摘要： Achievement of very smooth cavity sidewalls by UV picosecond laser micromachining. As a contactless and maskless method generating a reduced heat affected zone compared to nanosecond laser, ultrafast laser micromachining is widely used for rapid prototyping and materials processing. Today, most research and development works is devoted to study and control LIPPS occurring at the surface of the cavity bottom. But for many applications, there is a strong need to produce highly smooth sidewalls like for microelectronic sample preparation, microfluidics, waveguides, etc.. A laser based technology allowing to obtain very smooth surfaces (Ra of ~3 nm) already exists but it involves melting of a significant volume of material. So far, to the best of our knowledge, no parametric study aiming at minimizing the roughness of picosecond laser micromachined sidewalls in silicon has been performed. In the present work, picosecond laser micromachining (532 nm and 343 nm) of cavity sidewalls in silicon is studied. The evolution of the surface roughness is deeply investigated experimentally and theoretically as a function of laser and scanning parameters. We demonstrate that RaX, which is measured along the scanning laser beam direction, can be minimized by increasing laser beam overlap and the crater size, in accordance with a simple geometrical model. Experimentally, the minimum RaX is obtained for a beam overlap of ~80% and the largest crater sizes. Beyond 80%, we observed a roughness degradation which is probably due to two main phenomena. The first involves the interaction between the laser beam and the debris, which deteriorates the beam quality. The second is related to the highly heterogeneous ablation occurring for large overlaps, which induces a rough surface. Along the beam propagation direction, the sidewall is characterized by a relatively high waviness which induces a more important height variation than the roughness. The waviness depends mainly on the Rayleigh length. Thus, it can be reduced by using a large focal spot radius and a short wavelength. Once the sidewall is finished, the surface topology does not vary much with the laser micromachining time. Overall, smooth and homogeneous surfaces can be produced by choosing a beam overlap close to 80%. The best results were obtained at 343 nm, which allows to extend the Rayleigh zone, to increase the laser absorption on the sidewall asperities and to improve the induced cleaning thanks to a more confined interaction. The present work demonstrates that very low roughness (< 40 nm) can be achieved on sidewalls of cavities by picosecond laser micromachining. In addition this approach allows the roughness tuning. As it is based on a geometrical model, it is extendable to other materials as long as the surface melting, which may erase the induced periodic structuring, is not significant. This tuning possibility can be useful to modify the surface properties, such as reflectivity, friction and wettability, and therefore adapt the sidewall to different applications.
关键词： smooth cavity sidewalls,waviness,silicon,UV picosecond laser,roughness,micromachining,Rayleigh length
更新于2025-09-12 10:27:22
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High-performance oil-water separation polytetrafluoroethylene membranes prepared by picosecond laser direct ablation and drilling
摘要： The membranes with special surface wettability have attracted considerable attention, especially in the practical applications of oil-water separation. Here, we presented a simple and rapid method of picosecond (ps) laser direct ablation and then drilling to fabricate high-performance oil-water separation polytetrafluoroethylene (PTFE) membrane. It was found that the as-prepared rough PTFE membranes had ca. 0° contact angle (CA) of oil in air and above 150° CAs of water in air or oil, respectively, exhibiting superoleophilicity and under-oil superhydrophobicity. The micropore size of the membranes was less than ca. 180 μm, the corresponding separation efficiencies were over 99.0% for different oil-water mixtures due to the special and rough surface microstructures. Importantly, the separation efficiencies and fluxes of the as-prepared membranes showed no obvious change with suffering heavy erosion or 40 separation cycles, indicating that the membranes had excellent stability and applicability. Additionally, the effect of the special and rough surface on oil-water separation performance was investigated. This work provides a new pathway for the rapid fabrication of high-performance separation membranes.
关键词： Picosecond laser ablation,Superoleophilicity,Polytetrafluoroethylene,Superhydrophobicity,Oil-water separation
更新于2025-09-12 10:27:22
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Study the Effect of Changing the Surface Roughness and the Laser Focus Distance to the Aluminum Appearance using Picosecond Laser
摘要： Picosecond laser device is used to treat Aluminum samples, the appearance of the treated samples is affected by the variation of laser focus distance and the samples surface roughness. Samples with smoother surface before laser treatments show dark colors and high increase in surface roughness after laser treatments, while samples with rougher surfaces before laser treatments show brighter colors with slightly change in surface roughness after the laser treatments. The surface texture, topography, and roughness of the treated samples is characterized to identify the mechanism driving appearance change. The characterization results indicate that size and shape of laser processing induced microscale cavities on the surface may account for the differences in samples appearance.
关键词： Aluminum Appearance,Picosecond Laser,Focus Distance,Surface Roughness
更新于2025-09-12 10:27:22