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Radiation transport and scaling of optical depth in Nd:YAG laser-produced microdroplet-tin plasma
摘要： Experimental scaling relations of the optical depth are presented for the emission spectra of a tin-droplet-based, 1-lm-laser-produced plasma source of extreme-ultraviolet (EUV) light. The observed changes in the complex spectral emission of the plasma over a wide range of droplet diameters (16–65 lm) and laser pulse durations (5–25 ns) are accurately captured in a scaling relation featuring the optical depth of the plasma as a single, pertinent parameter. The scans were performed at a constant laser intensity of 1.4 (cid:2) 1011 W/cm2, which maximizes the emission in a 2% bandwidth around 13.5 nm relative to the total spectral energy, the bandwidth relevant for industrial EUV lithography. Using a one-dimensional radiation transport model, the relative optical depth of the plasma is found to linearly increase with the droplet size with a slope that increases with the laser pulse duration. For small droplets and short laser pulses, the fraction of light emitted in the 2% bandwidth around 13.5 nm relative to the total spectral energy is shown to reach high values of more than 14%, which may enable conversion ef?ciencies of Nd:YAG laser light into—industrially—useful EUV radiation rivaling those of current state-of-the-art CO2-laser-driven sources.
关键词： microdroplet-tin plasma,Nd:YAG laser,optical depth,radiation transport,extreme-ultraviolet (EUV) light
更新于2025-09-12 10:27:22
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Intraocular lens tilt and decentration after?Nd:YAG laser posterior capsulotomy: Femtosecond laser capsulorhexis versus manual capsulorhexis
摘要： To compare intraocular lens (IOL) tilt and decentration after Nd:YAG laser posterior capsulotomy in eyes that had femtosecond laser–assisted capsulotomy versus manual capsulorhexis. Setting: Ekol Eye Hospital, Izmir, Turkey. Design: Retrospective case series. Methods: Intraocular lens decentration and angle of tilt were measured using a Scheimpflug camera before and 1 month after Nd:YAG capsulotomy. Results: Eighteen eyes had a femtosecond laser–assisted capsulotomy and 25 eyes a manual capsulorhexis. The mean age was 58.2 years G 10.2 (SD) (range 44 to 69 years) and 60.6 G 8.3 years (range 45 to 70 years), respectively. Before capsulotomy, tilt and decentration at both meridians did not differ significantly between the 2 groups (P > .05). After capsulotomy, the angle of tilt was significantly decreased in both groups (femtosecond: vertical 1.5 degrees and horizontal 1.2 degrees; manual: vertical 1.1 degrees and horizontal) and decentration was significantly increased (femtosecond: vertical 0.085 mm and horizontal 0.096 mm; manual: vertical 0.2 mm and horizontal 0.2 mm) at both meridians (P < .05). After capsulotomy, all tilt and decentration parameters were significantly different between the 2 groups (P < .05) except decentration on the horizontal meridian (P Z .669). Conclusions: Nd:YAG posterior capsulotomy performed after femtosecond laser–assisted capsulotomy resulted in better mechanical stability of the IOL. This suggests that a femtosecond laser–created capsulotomy better maintains a proper IOL position. Although the differences were statistically significant, the tilt and decentration values were small and might not be clinically significant.
关键词： tilt,Nd:YAG laser,manual capsulorhexis,intraocular lens,femtosecond laser,decentration,posterior capsulotomy
更新于2025-09-12 10:27:22
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Laser treatment of epidermal nevi: A multicenter retrospective study with long-term follow-up
摘要： Background: Patients with epidermal nevi strongly demand cosmetic improvement. Laser treatment appears appealing and is frequently used in clinical practice. Nevertheless, large series with long-term follow-up are missing, preventing definitive conclusions about its real benefit. Objective: To evaluate the long-term effectiveness and safety of lasers for epidermal nevi. Methods: Bicentric, retrospective, cohort study, including all patients treated with a laser for an epidermal nevus with more than a one-year follow-up. Results: Seventy patients were treated for different types of epidermal nevi, mostly with ablative lasers: 23 verrucous epidermal nevi, 16 nevi sebaceous, 26 Becker nevi, two inflammatory linear verrucous epidermal nevi, one smooth-muscle hamartoma, one rounded and velvety epidermal nevus, and one nevus lipomatosus superficialis. The follow-up period ranged between 12 and 127 months (median 37 months). Better results, fewer recurrences, and higher patient satisfaction were noted in treatments for verrucous epidermal nevi than for nevi sebaceous. Q-switched (QS) lasers failed to show any degree of improvement in almost all patients with Becker nevus. Limitations: The retrospective nature of the study. Conclusions: Ablative lasers can treat verrucous epidermal nevi with good long-term esthetic results, but they have limited long-term efficacy for nevus sebaceous. Q-switched lasers failed to improve Becker nevi.
关键词： Epidermal nevus,Becker nevus,ILVEN,nevus lipomatosus superficialis,ablative laser,Er:YAG laser,CO2 laser,verrucous epidermal nevus,Becker’s nevus,nevus sebaceous,smooth-muscle hamartoma
更新于2025-09-12 10:27:22
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Evaluation of the Effects of Er:YAG Laser for the De-Epithelialization of the Palatal Graft in the Treatment of Multiple Gingival Recessions: A Randomized Clinical Trial
摘要： Objective: The purposes of this split-mouth pilot study were to investigate the efficacy of the Er:YAG laser use for the de-epithelialization of the palatal graft in the treatment of the multiple gingival recessions using the bilaminar procedure and also to evaluate the patient-reported esthetic outcomes after 6 months. Materials and methods: Five systemically healthy participants with total 28 bilateral-multiple adjacent maxillary Miller I recessions were included. The treatment was performed with the bilaminar technique [coronally advanced flap (CAF)+de-epithelialized free gingival graft]. De-epithelialization procedure was done with scalpel (control site) or Er:YAG laser (Versawave, Hoya ConBio, San Francisco, CA; 40 hz, 50 mJ/pulse), under water irrigation, noncontact mode (*1 mm away from the target tissue) in sweeping motion with chisel-type laser (test site). Root coverage and patient-reported outcomes were evaluated at 6 months after the operations. Results: Clinical outcomes of the both treatment sites did not show any statistically significant differences except for the gingival thickness parameter. However, patient-reported outcomes regarding the esthetic appearance of the gingiva was detected in favor of the Er:YAG laser applied sites. Conclusions: Within the limits of the study, it can be concluded that both de-epithelialization techniques were highly effective at 6 months. However, Er:YAG laser-applied grafted sites revealed more uniform and esthetic gingival appearance compared with scalpel-used grafted sites.
关键词： de-epithelialization,Er:YAG laser,bilaminar technique,gingival recession
更新于2025-09-12 10:27:22
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Management of a laryngeal venous malformation with Nd:YAG laser and bleomycin sclerotherapy
摘要： Literature describing neodymium:yttrium-aluminum-garnet (Nd:YAG) photocoagulation and sclerotherapy for laryngeal venous malformations (VMs) is sparse. Here we present a case in which an extensive laryngeal VM in a 28-year-old female was managed through a combination of four serial Nd:YAG laser photocoagulation sessions and four bleomycin injections over the course of 2 years. The treatment plan resulted in noticeable lesion ablation, mucosalization, and significant improvement in symptoms. To our knowledge, this case is the first instance of bleomycin injection specifically into a laryngeal VM reported in the English medical literature.
关键词： Nd:YAG laser,bleomycin sclerotherapy,photocoagulation,laryngeal venous malformation
更新于2025-09-12 10:27:22
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Effect of Q‐switched Nd‐YAG laser on the clinical, pigmentary and immunological markers in the patients with lichen planus pigmentosus: A pilot study
摘要： The persistent discolouration in lichen planus pigmentosus is secondary to persistent melanophages in superficial dermis in these patients. We evaluated the effect of Q-switched Nd-YAG laser on the clinical, pigmentary and immunological markers in the patients with lichen planus pigmentosus. Nine females with a clinical diagnosis of lichen planus pigmentosus were included in the study. After six sessions of laser with toning protocol, performed over a representative area of 5x5 cm2 at 2-weekly intervals, the mean clinical improvement as per the physician assessment was 25.7% (10-40%). There was no significant reduction in melanin and erythema index. On expression analysis using reverse transcriptase polymerase chain reaction, the reduction in tyrosinase (p=0.03) was statistically significant, though, the reduction in other pigment and immunological markers was not significant. The immunohistochemistry quantification data of corresponding proteins also did not show any significant difference. Post inflammatory hypopigmentation was noted in one patient. Q-switched Nd-YAG laser toning protocol resulted in modest clinical and histological improvement in patients of lichen planus pigmentosus.
关键词： Lichen planus pigmentosus,Q-switched Nd-YAG laser,melanophages
更新于2025-09-12 10:27:22
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2?kHz single-frequency, injection-seeded Q-switched laser with a ‘double-reflection’ architecture
摘要： A high-repetition-rate single-frequency injection-seeded Q-switched Er:YAG laser with a ‘double reflection’ architecture is reported. Single-frequency laser pulses at a pulse repetition frequency (PRF) of 2 kHz are obtained by using ‘ramp-fire’ injection-seeding technique. The half-width of the pulse spectrum is measured to be 2.05 MHz by using the heterodyne beating technique. The novel ‘double-reflection’ architecture is employed in order to achieve a stable high-repetition-rate single-frequency operation. As far as we know, 2 kHz is the highest PRF achieved from a single-frequency, injection-seeded Q-switched Er:YAG laser that can be used in a wind Lidar system.
关键词： single-frequency lasers,eye-safe lasers,solid-state lasers,Q-switching,diode-pumped lasers,injection-seeding,Er:YAG lasers
更新于2025-09-12 10:27:22
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Experimental Investigation Of Quality Characteristics In Nd:YAG Laser Drilling Of Stainless Steel (AISI 316)
摘要： Micro-machining of advanced engineering materials such as stainless steels, titanium alloys, nickel alloys, and ceramics is a challenging task due to properties like high strength to weight ratio, toughness, slenderness ratio, and low thermal conductivity. Stainless steel of grade AISI 316 has wide applications in medical science, automobile engineering, aviation, and aerospace industry due to their favourable material properties such as low thermal conductivity, high corrosion resistance, and high strength to weight ratio. Micro-machining of AISI 316 with high aspect ratio is a difficult task due to excessive heat generation, micro- structural changes, and tool breakage. Laser beam machining (LBM) process is a suitable alternative machining process, since it localizes the heat source to control the micro-structural changes. The difficulty arises during laser drilling because of spatter area and heat affected zone (HAZ), which adversely affects the quality of laser drilled holes. The present study attempts to experimentally investigate the effect of laser process parameters such as pulse width, laser energy, pulse frequency, and flushing pressure on the performance measures such as spatter deposition and heat affected zone (HAZ) during drilling operation. To reduce the total number of experimental run and obtain maximum information for the experimental trials, Taguchi L27 has been adopted. Analysis of variance (ANOVA) is performed to identify significant laser parameters influencing both the performance measures. From the study, it is revealed that pulse width is the most significant parameter in the formation of spatter and HAZ. From the results, it is identified that spatter area initially increases with increase in pulse frequency and then decreases for any level of pulse width. As pulse frequency increases, laser power increases resulting in more heat input into the material. This causes increase in vapour pressure inside the laser drilled hole, more material ejection, and increase in spatter area. However, laser supported absorption (LSA) waves developed at higher value of pulse frequency brings about blockage of laser energy from the material surface as an engrossing plasma, which results in reduction of material ejection and reduction in spatter area. It is observed that HAZ increases with increase in pulse width and pulse frequency. It may be due to higher average power of the laser beam, which is directly proportional to pulse width and pulse frequency. Higher the value of pulse width, higher will be the laser thermal energy and higher HAZ.
关键词： Laser Drilling,Nd:YAG Laser,HAZ,Spatter
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) - Dual Function Thin Slab Ultrafast Amplifier Producing 240W over a Range of Pulse Repetition Frequencies
摘要： Applications for ultrashort pulse (<100ps) laser systems are developing at an increasing rate. Broadly, the applications can be categorized as (a) low pulse repetition frequency (PRF) <1MHz, athermal machining with moderate pulse energies, and (b) high PRF, >1MHz highly localized (and controlled) melting with lower pulse energies. Ideally, a single technology platform should address the entire range of applications whilst providing the necessary average power to achieve productivity targets. Fibre based systems are ideally suited for average power scaling beyond the kilowatt level whilst maintaining excellent beam quality, although peak powers and pulse energies are limited by non-linear effects [1]. Therefore, bulk systems with carefully designed thermal management, such as thin disks, thin slabs and single crystal fibres have become dominant technologies for power and energy scaling of ultrashort pulse systems [2-5]. However, these configurations can result in limitations in frequency, power or energy. This paper reports results obtained for a single crystal thin slab amplifier configured in a novel integrated pre-amplifier/power-amplifier architecture that overcomes many of the limitations of the alternative technologies whilst creating a more compact device [6]. The output power is essentially independent of seed power, and pulse-picked PRF, for a significant range of frequencies, provided pulse energy damage thresholds are not exceeded.
关键词： ultrashort pulse,pulse repetition frequency,laser systems,thin slab amplifier,Yb:YAG
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) - Eye-Safe Er:YAG Laser Q-Switched by Co:Spinel Saturable Absorber
摘要： The aim of this work was to investigate the utilization of Co:Spinel as saturable absorber for eye-safe Er:YAG laser generating at 1645 nm wavelength. Co:Spinel (Co:MgAl2O4, Co:MALO) absorber is used to Q-switching for laser systems generating about 1.5 μm wavelength, for example for Er:glass laser. Due to lower radiation absorption above the 1.55 μm wavelength of Co:spinel, the another passive absorbers were investigated, e.g. U:SrF2 [1], Co:GSGG [2], and Cr:ZnSe [3]. However, the advantage of Co:Spinel is its high damage threshold and therefore, the research of its utilization would be prolonged, especially for 1.6 μm Er:YAG laser.
关键词： eye-safe laser,saturable absorber,Er:YAG laser,Q-switching,Co:Spinel
更新于2025-09-12 10:27:22