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How Lasers Ablate Stones: In-vitro Study of Laser Lithotripsy (Ho:YAG and Tm-fiber lasers) in Different Environments
摘要： Introduction. There are two main mechanisms of stone ablation with long‐pulsed infrared lasers: photothermal and photomechanical. Which of them is primary in stone destruction is still a matter of discussion. Water holds importance in both mechanisms but plays a major role in the latter. We sought to identify the prevailing mechanism of stone ablation by evaluating the stone mass‐loss after lithotripsy in different media. Material and methods. We tested a Ho:YAG laser (100W, Lumenis, USA), a Tm‐fiber laser U1 (TFL U1), (120W, NTO IRE‐Polus, Russia) and a Superpulse Tm‐fiber laser U2 (TFL U2) (500W, NTO IRE‐Polus, Russia). A single set of laser parameters (15 W = 0.5 J × 30 Hz) was used. Contact lithotripsy was performed in phantoms (BegoStones) in different settings: a) hydrated phantoms in water; b) hydrated phantoms in air; с) dehydrated phantoms in water; d) dehydrated phantoms in air. Laser ablation was performed with total energy of 0.3 kJ. Phantom mass‐loss was defined as the difference between the initial phantom mass and the final phantom mass of the ablated phantoms. Results. All lasers demonstrated effective ablation in hydrated phantoms ablated in water, no visual differences between the lasers were detected. The ablation of dehydrated phantoms in air was also effective with visible vapor during ablation and condensation on the cuvette wall. Dehydrated phantoms in water and in air shown minimal to no ablation accompanied with formation of white crust on phantoms surface. Among laser types, TFL U2 had the highest phantom mass‐loss in all groups except for dehydrated phantoms ablated in air. Conclusions. Our results suggest that both photothermal and thermomechanical ablation mechanisms (explosive vaporization) occur in parallel during laser lithotripsy. In Ho:YAG and TFL U2 stone ablation, explosive vaporization prevail, while in TFL U1 ablation, photothermal mechanism appear to predominate.
关键词： laser lithotripsy,Ho:YAG laser,Thulium fiber laser,stone disease
更新于2025-09-12 10:27:22
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Treatment of Congenital Melanocytic Nevi in the Eyelid and Periorbital Region With Ablative Lasers
摘要： Background: Congenital melanocytic nevi (CMN) that occur on the eyelid and periorbital region cause cosmetic disfiguring. Laser treatment has aroused interest as an alternative treatment method, and resurfacing lasers have shown promising results. Objective: This study aimed to evaluate the efficacy and safety of carbon dioxide laser and erbium:yttrium aluminum garnet laser to treat CMN of the eyelid and periorbital region. Methods and Materials: Twenty patients with CMN were included in this study and were treated with either the CO2 or erbium:yttrium aluminum garnet laser. Clinical efficacy outcomes were evaluated by visual assessment and L*a*b* color space evaluation at least 6 months after treatment. Results: The average (SD) visual evaluation improvement, assessed on a 5-point scale, was 2.8 (1.27). The mean (SD) values of the relative L* improvement rate and blanching rate of the CMN lesion were 32.0% (47.9%) and 34.1% (36.2%), respectively. Spearman rank correlation coefficient between the objective and subjective evaluations was significant (P < 0.001). Three cases developed partial hypopigmentation. No patient developed hypertrophic scars. Conclusion: The outcomes after laser treatment were variable, although half of the patients achieved greater than 50% clearance. It provides an alternative to surgical excision for the removal of CMN in the difficult regions. Surgery excision is inevitable for some patients.
关键词： carbon dioxide laser,eyelid and periorbital region,congenital melanocytic nevi,ablative laser,Erbium:YAG laser
更新于2025-09-12 10:27:22
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Nd <sup>3+</sup> :YAG laser based on the <sup>4</sup> F <sub/>3/2</sub> → <sup>4</sup> I <sub/>13/2</sub> secondary transition with a phase-conjugate electro-optically Q-switched open multiloop cavity
摘要： Lasing on the 4F3/2 → 4I13/2 secondary transition (λ = 1.34 μm) in a Nd3+ : YAG laser with phase conjugation by four-wave mixing directly in the active laser medium was experimentally studied in the regime of electro-optic Q-switching of an open multiloop cavity. The use of an electro-optic Q-switch with a controllable delay of its opening made it possible to increase the amplitude and temporal stabilities of the output laser parameters. The maximum laser pulse energy was 100 mJ at a pulse duration of 120 ns. The phase-conjugate radiation divergence was 0.8 mrad at beam quality Mx2 = My2 = 1.3. Nonlinear optical conversion of 1.34 μm laser radiation to visible radiation was achieved experimentally. Second and third harmonic generation at wavelengths of 0.67 and 0.446 μm with conversion efficiencies of 25 % and 8 %, respectively, was demonstrated.
关键词： phase conjugation,secondary transition,stability of laser parameters,Nd3+ : YAG laser,electro-optic Q-switching
更新于2025-09-12 10:27:22
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Multi‐Factors Associated With Efficacy and Adverse Events of Fractional Erbium:YAG Laser‐Assisted Delivery of Topical Betamethasone for Stable Vitiligo: A Retrospective Analysis
摘要： Background and Objectives: Although topical corticosteroids are still the first‐line option for vitiligo, its efficacy is still unsatisfactory for stable vitiligo. A few studies have focused on laser‐assisted drug delivery (LADD) but were limited by their sample deficiency and analyses of the influencing factors. To determine the efficacy, adverse events, and their influencing factors of fractional erbium: yttrium‐aluminum‐garnet (Er:YAG) laser‐assisted topical delivery of corticosteroids in stable vitiligo. Study Design/Materials and Methods: We retrospectively reviewed 1,026 lesions in 684 patients with stable vitiligo who underwent treatment with fractional Er:YAG laser‐assisted delivery of topical compound betamethasone solution between January 2014 and December 2017. Multi‐factors associated with different outcomes were analyzed by logistic regression in this study. Results: A total of 413 of 1,026 lesions (40.3%) were effective 12 months after the first treatment. Age (<14 years old), disease duration (<1 year), lesion location (on face and neck), hairy lesions, and drug concentration were independent factors associated with effective repigmentation. A common adverse event was hyperpigmentation (14.4%), which was highly correlated with 22% density. Conclusions: Fractional Er:YAG laser‐assisted delivery of topical compound betamethasone is a good option for the management of vitiligo. The treatment may be suggested in these situations: younger patients, shorter disease duration, and lesions on the face and neck with hair. The appearance of white hair in the lesion area does not affect our confidence in vitiligo treatment. Density >22% may cause hyperpigmentation, but it does not significantly contribute to the efficacy.
关键词： betamethasone,laser‐assisted drug delivery,fractional Er:YAG laser,vitiligo,repigmentation
更新于2025-09-12 10:27:22
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Erbium:YAG laser treatment of female stress urinary incontinence: midterm data
摘要： Introduction and hypothesis Stress urinary incontinence (SUI) is treated using intravaginal laser therapy. We wanted to find out how incontinence severity at baseline and the number of laser interventions affect success rate, and whether the effect of laser therapy was obvious 6 months and 2 years after the last laser intervention. Methods Fifty-nine women, 32 with SUI I, 16 with SUI II, and 11 with SUI III were treated using an erbium-doped yttrium aluminium garnet (Er:YAG) laser following the IncontiLase? protocol. Therapy included five laser sessions with a 1-month interval between sessions. Objective (1-h pad test) and subjective data (International Consultation on Incontinence Questionnaire-Urinary Incontinence Short Form [ICIQ-UI SF], Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire [PISQ-12]) were assessed at baseline, after two and four laser sessions and 6 months and 2 years after the fifth laser session. Results Objective cure/improve rates for mild SUI I were 69%, 78%, 91%, and 78% after two, four, and five laser sessions at the 6-month and 2-year follow-ups. Subjective cure rates (ICIQ-UI SF) were 53%, 69%, 72%, and 66%, and sexual function (PISQ-12) also improved. For SUI II, objective cure/improve rates were 31%, 63%, 69%, and 50%. Subjective cure rate was 13% at the 2-year follow-up. For SUI III, only one patient had an objective improvement after two and four laser sessions. Conclusions Intravaginal laser therapy led to cure/improvement for SUI I and SUI II, but not for severe SUI III. Outcome was better after four to five laser sessions than after two laser sessions. Follow-up data 6 months and 2 years after laser intervention showed sustainability of the treatment.
关键词： ICIQ-UI SF,1-h pad test,Stress urinary incontinence,Intravaginal laser therapy,Erbium:YAG laser,Non-ablative SMOOTH mode
更新于2025-09-12 10:27:22
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Effect of the surface texturing treatment with Nd: YAG laser on the wear resistance of CoCr alloy
摘要： The present work aims to explore the tribological behavior of the laser texturing process with different patterns on a Co based alloy using a pulsed Nd: YAG laser. Different parameters such as peak power, speed and spot diameter of the laser were explored for the experimental setting. The microstructural analysis was performed using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and nanoindentation tests. The influence of the different textured patterns of the tribological performance tested with a pin-on-disc tribometer under lubricated sliding condition was evaluated. The results showed that typical interdendritic structures in the as-cast CoCr alloy condition were refined due to the heat input and fast cooling rate during the laser treatment. The refined microstructure showed less volumetric loss resulting in a increment of wear resistance and a better tribological performance than as-cast alloy. The correlation among laser parameters, microstructural effect and their influence in wear resistance is discussed.
关键词： Nd: YAG laser,laser texturing,CoCr alloy,tribological behavior,wear resistance
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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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) - 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
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Proton generation from hydrocarbon polymer targets for laser ion source
摘要： A laser ion source can provide intense pulsed ion beams from a solid target. On the other hand, generation of a proton beam with a laser ion source requires using compound targets containing hydrogen. In this research, we demonstrated proton generation from three kinds of hydrocarbon polymer targets: polyethylene (C2H4)n, polypropylene (C3H6)n, and polystyrene (C8H8)n. The laser used was a Nd:YAG laser (532 nm/17 ns), and the energy was 0.2 J. The ion current and the fraction of ion species were measured using a Faraday cup and an electrostatic ion analyzer. The results indicated that the peak currents and fraction to total particle number of proton were similar for the different hydrocarbon polymer targets and also showed that increasing the laser intensity effectively increases the number of proton particles because the larger the laser intensity, the larger the total charge.
关键词： hydrocarbon polymer targets,Nd:YAG laser,proton generation,electrostatic ion analyzer,ion current,laser ion source
更新于2025-09-12 10:27:22