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Effect of the Synthesis Method on the Properties of Ultrafine YAG Powder
摘要： Yttrium aluminum garnet (YAG) materials have a number of unique properties, such that its application is extensive. In this study, ultrafine YAG powder materials were prepared by coprecipitation and hydrothermal precipitation methods. The influence of the synthesis process on the morphology of the powder was investigated. Results showed that the precursor powder prepared via the coprecipitation method mainly undergoes amorphous to crystalline transition with the increase in calcination temperature and that the precursor agglomeration is severe. In the process of increasing the calcination temperature, the dispersibility of the roasted powder is considerably improved, which is favorable for the growth of the crystal grains, such that the particle size of the powder is gradually increased. The YAG precursor prepared by the coprecipitation method is transformed into YAG crystals, with the phase transition mainly occurring between 900 °C and 1,100 °C. When the molar ratio of salt to alkali is Y3+/OH?=1:8 via the hydrothermal reaction, YAG particles with homogeneous morphology can be obtained. When the molar ratio of salt to alkali is continuously increased, the morphology of YAG particles is not obviously changed. The coprecipitation method is used to control the particle size, whereas the hydrothermal method is used to control the particle morphology.
关键词： co-precipitation method,hydrothermal precipitation method,ultra-fine powder,YAG
更新于2025-09-23 15:21:01
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Spectral photoluminescence properties of YAG: Ce, R (R: Gd3+, Pr3+, Gd3+ and Pr3+) transparent fluorescent thin film prepared by pulse laser deposition
摘要： In order to overcome the shortcomings of insufficient red light component and poor thermal stability of commercial white light emitting diode (WLED), YAG:Ce, R (R: Gd3t and Pr3t) fluorescent thin films were prepared by pulse laser deposition (PLD). The composition and microstructure, photoluminescence properties, and red-enhanced mechanism of co-doped YAG fluorescent thin films, as well as the electroluminescence behavior of the corresponding WLEDs were investigated. Results showed that the doping of Pr3t caused the emission spectrum energy of Ce3t to migrate, and an emission peak appeared at 606 nm in the red region. The doping of Gd3t caused the emission spectrum of Ce3t to shift to the red region, and the main peak position of the Ce3t emission spectrum is red-shifted from 523 nm to 548 nm. The YAG:Ce,Pr,Gd fluorescent film not only realized the improvement of red light components and red-shift, but also increased the energy transmission efficiency from 33.3% to 51.9%. Moreover, results of the color coordinate analysis also showed that the co-doping of Gd3t and Pr3t made the luminescence closer to the red region, reducing the color temperatures and hues changed to warm. Thus, tri-doped transparent fluorescent thin film were prospective for WLED application.
关键词： Photoluminescence properties,Transparent thin film,Pulse laser deposition,YAG:Ce,Tri-doped YAG
更新于2025-09-23 15:19:57
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Q-Switched and Mode-Locked Nd/Cr:YAG Ceramic Pulse Laser
摘要： A mode-locked and Q-switched short pulse laser using the Nd3+/Cr3+:YAG ceramic has been constructed with a SESAM and Cr4+:YAG crystal optical switch based on excite state absorption (ESA). Laser oscillations of the pulse laser were observed experimentally. The Nd/Cr:YAG ceramic laser has a high conversion e?ciency from white light (such as lamp light or solar light) to the laser. The Nd/Cr:YAG ceramic has a higher laser gain than the Nd:YAG laser for the same pumping power. The laser oscillation can be obtained very easily. A single-mode-locked laser pulse with fast modulation on the order of 100 ps was obtained in some pump power regimes when using the Cr4+:YAG crystal. The obtained pulse duration of the short pulse was a few hundred ps. A maximum peak power of 60 kW was obtained when using a SESAM. The same level of peak power (60 kW) was also obtained when using the Cr4+:YAG crystal.
关键词： Q-switched,Nd/Cr:YAG ceramic,mode-locked,pulse laser,Cr4+:YAG crystal,SESAM
更新于2025-09-23 15:19:57
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Optimal settings for the Holmium: YAG laser in pediatric endourology: tips and tricks
摘要： To the best of our knowledge, no pediatric paper has been published regarding specifically how to set the Holmium:YAG laser for multiple urologic applications. Objective: To provide insight into the laser parameters for pediatric applications Study design: We describe the principle and the settings of the laser Results: The Holmium:YAG laser can produce four different biological effects: (1) fragmentation of stones in small fragments that can be retrieved with grasping instruments, thereby increasing the immediate stone-free outcome. For fragmentation lithotripsy, the laser has to be set with a high energy, low frequency and short pulse duration; (2) dusting which produces fine dust that can spontaneously evacuate, avoiding the use of basket retrieval. The dusting setting requires low energy, high frequency and long pulse duration; (3) incision of posterior urethral valves or ureterocele when all settings are maximized: high energy, high frequency and long pulse duration; (4) coagulation of urothelial tumors using high frequency, long pulse duration and slightly lower energy than required for incision. Discussion: Both dusting by painting and fragmentation with retrieval for ureteroscopic laser lithotripsy are effective. Although dusting tends to be associated with shorter operative times and a lower risk of ureteral trauma, this approach has a potential risk of recurrent stone formation from dust failing to pass. In contrast, fragmentation with extraction may provide for a more immediate postoperative stone-free result. Altering the pulse energy, frequency, width and modulation can help to optimize lithotripsy efficiency. Lower pulse energy settings result in smaller fragments, less retropulsion and reduce fiber tip degradation. A shallow depth of penetration in water and tissue allows precise energy application and provides a margin of safety. Conclusion: An understanding of Ho-YAG laser settings will permit the pediatric surgeon to make a better use of the device for different urological applications.
关键词： children,dusting,fragmentation,section,laser Holmium-YAG
更新于2025-09-23 15:19:57
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Modelling and optimization of process parameters to obtain maximum tensile strength for laser butt welding of 316L austenitic stainless steel sheets
摘要： The attribute of high power density but low energy-input in Laser welding offers exciting solutions to the commonly encountered disadvantages with conventional joining techniques. In this paper, 316L Austenitic Stainless Steel metal sheets were butt welded using Nd:YAG Laser welding system. Owing to its low cost and specific properties such as excellent toughness, higher creep, stress to rupture at elevated temperatures, 316L A.S.S finds wide range of applications in the industrial arena especially in the automobile and marine sectors. Hence, it becomes imperative to examine its post weld properties after performing laser welding and find optimized values of the parameters. The prominent process parameters like Laser Power, Travel speed and Focal length were analysed and optimised. Design of experiment statistical tool was embraced for the systematic conduct of the tests. Response Surface Methodology (RSM) and analysis of variance (ANOVA) techniques were employed to identify the significant process parameters affecting the weld. An empherical relationship involving the parameters was developed to predict the ultimate tensile strength. The 3D response surface plot and contour plots were generated for this model to elucidate the interaction effect of Laser parameters (Travel speed and Focal length), (Laser Power and Focal Length) & (Laser Power and Travel Speed) on Ultimate Tensile Strength. The welded specimens cut by electric discharge machining were prepared for tensile testing as per the ASTM standard. The Universal Testing Machine was used to test the welded specimen. Microhardness Testing was also carried out on the base material and the Heat Affected Zone (HAZ) using Vickers Hardness Testing machine. The tensile tested specimens were used for metallurgical analysis using Scanning Electron Microscope (S.E.M.). Specimen prepared for metallurgical analysis were sectioned, mounted, ground and polished in accordance with recommended procedures in ASTM practice E 3-11. The metallurgical observations showed the existence of undulating topography of ductile fracture surfaces. The investigations reveals that the actual values of the Ultimate tensile strength of the weld were falling close with the predicted strength obtained through the proposed model. It can be concluded that the proposed model in this work can be utilised to predict tensile strength of the weld with more precision.
关键词： Design of Experiments,Ultimate tensile strength,316 L A.S.S,Response Surface Methodology (RSM),Nd:YAG Laser welding
更新于2025-09-23 15:19:57
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Face and neck rejuvenation using an improved non-ablative fractional high power 1064-nm Q-switched Nd:YAG Laser: clinical results in 16 women
摘要： Objective: To evaluate the safety and efficacy of a specific treatment protocol using a new and improved non-ablative fractional high-power 1064-nm Q-switched Nd:YAG laser for face and neck rejuvenation. Methods: Sixteen women, aged 30 to 60 years old, were selected to undergo three consecutive treatment sessions with this new laser at maximum energy (2,400 mJ/pulse, Clear Lift laser?-Harmony XL-Pro, Alma Lasers Ltd.). Face and neck were treated in eight patients, respectively. Each treatment used the same protocol. The efficacy was evaluated by the therapist (TS), the patient (PS), and two separate independent experts who were blind to the study (E1 and E2). Results: According to E1 and E2, the mean reduction in signs of skin aging on a Global Esthetic Improvement Scale was 30-40%. Using a 0–10 points scale, TS and PS mean (range) satisfaction rates were 9.0 (8–10); 9.2 (6–10) for the face and 8.7 (8–10); 8.0 (3–10), for the neck, respectively. The procedure was practically painless, no significant adverse effects were observed, and the patients returned to their daily and work activities without downtime. Conclusion: This laser was safe and effective for face and neck minimally invasive rejuvenation, with excellent results using our usual routine use conditions.
关键词： fractionated laser,resurfacing,Q-Switched Nd:YAG laser,Skin rejuvenation,non-ablative laser
更新于2025-09-23 15:19:57
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Ytterbium laser system for studying parametric amplification of femtosecond pulses with a centre wavelength of a??2 ??m
摘要： A laser system is developed with an optical synchronisation of a femtosecond signal with a pump channel. The signal of a driving ytterbium fibre laser with a 60 MHz repetition rate of stretched femtosecond pulses is amplified in energy from several nanojoules to 0.4 mJ at a pulse repetition rate of 3 kHz in a wide-band amplifier and then is compressed in time to 250 fs. The obtained radiation is used for generating femtosecond laser pulses with a centre wavelength of ~2 mm, pulse energy of above 20 mJ, duration of several field oscillations, and phase stabilisation between the electromagnetic field and envelope. The other pulse of the driving fibre laser provides optical synchronisation and a minimal time delay and is directed to a regenerative Yb : YAG disk amplifier for amplification to an energy of 4 mJ at a pulse repetition rate of 3 kHz and duration of 20 ps. A multipass disk amplifier is developed for further increasing the energy of pump chirped pulses to an energy of 70 mJ at a pulse repetition rate of 10 Hz and duration of 400 ps for studying parametric amplification under sub-nanosecond pumping.
关键词： parametric amplification,Yb :YAG disk amplifier,ytterbium fibre laser,femtosecond pulses,pulse compression
更新于2025-09-23 15:19:57
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Evaluation of Fractional CO <sub/>2</sub> Versus Long Pulsed Nd:YAG Lasers in Treatment of Hypertrophic Scars and Keloids: A Randomized Clinical Trial
摘要： Background: Keloids and hypertrophic scars are challenging to both patients and physicians. They can be aesthetically disfiguring, functionally debilitating, and emotionally distressing. Lasers have introduced new mechanisms to improve scars both on aesthetic and symptomatic levels. Aim of Work: Comparing the efficacy of fractional CO2 laser, long‐pulsed Nd:YAG laser and their combination in the treatment of hypertrophic scars and keloids on clinical, histopathological, and biochemical basis. Patients and Methods: Thirty patients with hypertrophic scars and keloids were enrolled in the study. Three scars in each patient were randomly assigned to treatment modalities (i) Fractional CO2, (ii) Nd:YAG laser, (iii) Combined CO2 and Nd:YAG lasers. For each treatment area four sessions, 4–6 weeks apart were performed. Clinical evaluation was done before and 1 month following last session using the Vancouver Scar Scale (VSS) and the Patient and Observer Scar Assessment Scale (POSAS). Routine hematoxylin and eosin, Masson's trichrome, and Orcein stains were used to evaluate the appearance and pattern of dermal collagen and elastic fibers. Image analysis was used to quantitatively assess the density of collagen and elastic fibers. Biochemical evaluation of tissue level of transforming growth factor‐β I (TGF‐β I) and TGF‐β III was performed using enzyme‐linked immunosorbent assay studies. Results: Both VSS and POSAS showed significant improvement following treatment with the three used modalities. Collagen fibers showed significant improvement as regards appearance and pattern while it was insignificant as regards density. Elastic fibers density improvement was only significant in fractional CO2 (treatment area A). Hypertrophic scars showed more significant improvement with fractional CO2 laser, while in keloids there was no significant difference between the three modalities regarding improvement. Level of TGF‐β I showed significant reduction after treatment in all treatment modalities, while TGF‐β III levels showed insignificant elevation in all treatment modalities. Side effects were significantly higher in treatment area C (combined treatment). Conclusion: Long pulsed Nd:YAG laser is effective and safe treatment of hypertrophic scars and keloids. Fractional CO2 laser yields better improvement in hypertrophic scars, while in keloids both fractional CO2 and Nd:YAG lasers achieve comparable improvement. Combination in the same session did not add significant additional benefit and the side effects profile was higher. Limitations: small sample size and short follow‐up period.
关键词： fractional CO2 laser,Nd:YAG laser,keloids,hypertrophic scars,RCT
更新于2025-09-23 15:19:57
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Effect of a topical antioxidant serum containing vitamin C, vitamin E, and ferulic acid after Qa??switched 1064a??nm Nd:YAG laser for treatment of environmenta??induced skin pigmentation
摘要： Background: Extrinsic skin aging caused by atmospheric pollutants is associated with a sustained inflammatory response which is a significant risk factor for lentigines and melasma. Aims: The aim of this study was to evaluate the efficacy of topical application of combination formulation of vitamin C, vitamin E, and ferulic acid as an adjuvant to Q-switched Nd:YAG (QSNY) lasers treatment in individuals with lentigines and melasma. Methods: A single blinded, prospective, randomized split-face trial was conducted. Eighteen men and women between 26 and 53 years old were treated with a combination antioxidant serum on one randomized side of their face immediately after QSNY laser and twice daily for 2 weeks. Patients were evaluated using digital photography and spectrometry to assess the melanin index and erythema index. Melasma severity score and global improvement scores also were assessed. Results: The treated side of the face exhibited a significantly greater reduction in the melanin index. There was no significant difference in post-treatment erythema. More clinical improvement was observed on the treated side compared with the untreated side. Conclusions: Our study suggests that topical application of a combination vitamins C, E, and ferulic acid antioxidant formula may be effective as an adjuvant option in QSNY lasers.
关键词： air pollution,lentigo,QS Nd:YAG laser,vitamin C,antioxidant
更新于2025-09-23 15:19:57
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Thermal coagulum formation and hemostasis during repeated multipulse Nd:YAG laser treatment of cutaneous vascular lesions: animal experiment study
摘要： Laser therapy has been widely used to treat port-wine stain (PWS) and other cutaneous vascular lesions via selective photothermolysis. High incident laser fluence is always prohibited in clinic to prevent the thermal damage in normal skin tissue, leading to insufficient energy deposition on the target blood vessel and incomplete clearance of PWS lesion. In this study, repeated multipulse laser (RMPL) irradiation was proposed to induce acute thermal damage to target blood vessels with low incident fluence (40 J/cm2 for 1064-nm Nd:YAG laser). The feasibility of the method was investigated using animal models. Repeated multipulse irradiation cycles with 10-min intervals were performed in RMPL. A hamster dorsal skin chamber model with a visualization system was constructed to investigate the instant generation of thermal coagulum and relevant hemostasis by thrombus formation during and after irradiation under 1064 nm Nd:YAG single multipulse laser (SMPL) and RMPL irradiation. The diameter of the target blood vessel and the size of thermal coagula were measured before and after laser irradiation. The reflectance spectra of the dorsal skin were measured by a reflectance spectrometer during RMPL. Stasis thermal coagula that clogged the vessel lumen were generated during SMPL irradiation with low incident fluence. However, there was no acute thermal damage of blood vessels. Reflectance spectra measurement showed that the generation of thermal coagula and subsequent thrombus formation increases blood absorption by more than 10% within the first 10 min after laser irradiation. Acute vessel thermal damage could be induced in the target blood vessel by RMPL with low incident fluence of 40 J/cm2. Compared with our previous SMPL study, nearly 30% reduction in incident laser fluence was achieved by RMPL. Low fluence RMPL may be a promising approach to improve the therapeutic outcome for patients with cutaneous vascular lesions by improving energy deposition on the target blood vessel.
关键词： Thermal coagula,1064-nm Nd:YAG laser,Port-wine stain,Repeated multiple pulse laser irradiation,Thrombus formation
更新于2025-09-23 15:19:57