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Influence of the Laser Wavelength on Harmful Effects on Granite due to Biofilm Removal
摘要： The colonization of stone-built monuments by different organisms (algae, fungi, lichens, bacteria, and cyanobacteria) can lead to biodeterioration of the stone, negatively affecting the artistic value of the heritage. To address this issue, laser cleaning has been widely investigated in recent years, due to the advantages it offers over traditional mechanical and chemical methods: it is gradual, selective, contactless, and environmentally friendly. That said, the laser parameters should be optimized in order to avoid any by-effects on the surface as a result of overcleaning. However, as the adjustment of each parameter to clean polymineralic stones is a difficult task, it would be useful to know the effect of overcleaning on the different forming minerals depending on the wavelength used. In this paper, three different wavelengths (355 nm, 532 nm, and 1064 nm) of a Q-Switch neodymium-doped yttrium aluminum garnet (Nd:Y3Al5O12) laser, commonly known as QS Nd:YAG laser were applied to extract a naturally developed sub-aerial biofilm from Vilachán granite, commonly used in monuments in the Northwest (NW)Iberian Peninsula. In addition to the removal rate of the biofilm, the by-effects induced for fluences higher than the damage threshold of the stone were evaluated using stereomicroscopy, color spectrophotometry, and scanning electron microscopy with energy-dispersive x-ray spectroscopy. The results showed that different removal rates were obtained depending on the wavelength used and 532 nm obtained the highest removal level. In terms of by-effects, biotite melting was registered on all surfaces regardless of the wavelength. In addition, 532 nm seemed to be the most aggressive laser system, inducing the greatest change in appearance as a result of extracting the kaolinite crackled coating and the segregations rich in Fe, which are a result of natural weathering. These changes were translated into colorimetric changes visible to the human eye. The surfaces treated with 355 nm and 1064 nm showed lower surface changes.
关键词： laser,granite,stone cleaning,cultural heritage,Nd:YAG,cleaning effectiveness
更新于2025-09-16 10:30:52
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How much energy do we need to ablate 1 mm3 of stone during Ho:YAG laser lithotripsy? An in vitro study
摘要： Introduction Holmium:yttrium–aluminium–garnet (Ho:YAG) is currently the gold standard for lithotripsy for the treatment of all known urinary stone types. Stone composition and volume are major determinants of the lithotripsy. This in?vitro study evaluated the required energy to ablate 1?mm3 of various stone types with different laser settings using Ho:YAG. Methods 272?μm core-diameter laser fibers (Boston Scientific?) were connected to a 30?Watt MH1 Ho:YAG generator (Rocamed?). An experimental setup consisting of immerged human stones of calcium oxalate monohydrate (COM), uric acid (UA) or cystine (Cys) was used with a single pulse lasing emission (0.6/0.8/1?J), in contact mode. Stones were dried out before three-dimensional scanning to measure ablation volume per pulse (AVP) and required energy to treat 1?mm3 (RE). Results All settings considered, ablation volumes per pulse (AVP) for COM were significantly lower than those for UA and Cys (p = 0.002 and p = 0.03, respectively), whereas AVP for Cys was significantly lower than those for UA (p = 0.03). The mean REs at 0.6?J pulse energy (PE) for COM, Cys and UA were 34, 8.5 and 3.2?J, respectively The mean REs at 1?J PE for COM, Cys and UA were 14.7, 6.4 and 2?J, respectively. At 0.6?J PE, RE for COM was more than tenfold and fivefold higher than those for UA and Cys, respectively. Conclusion This in?vitro study shows for the first time a volumetric evaluation of Ho:YAG efficiency by the ablation volume per pulse on human stone samples, according to various pulse energies. The REs for COM, UA and Cys should be considered in clinical practice.
关键词： Holmium YAG,Volume,Lithotripsy,Laser
更新于2025-09-16 10:30:52
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Third-order nonlinear optical response of Yb:YAG ceramics under femtosecond laser irradiation
摘要： Transparent ceramic laser materials, as an important alternate of traditional laser gain medium materials, have aroused much attention for their excellent performance. Here, we investigated the third-order nonlinear susceptibility of high quality transparent Ytterbium-doped Yttrium Aluminium Garnet (Yb:YAG) ceramics. Under an ultrafast femtosecond laser irradiation, we experimentally demonstrated the nonlinear optical limiting and self-focusing behaviors of Yb:YAG ceramic by Z-scan method at 800 nm. It was found that Yb:YAG ceramics exhibit a relatively small nonlinear refractive index (~3.8 × 10?20 m2/W) which exerts little dependence on the Yb3+ doping concentration and laser intensity. This work could illustrate the application potential of transparent ceramic under high-power condition and can also provide useful design guidelines for high power ceramic laser system.
关键词： Third-order optical nonlinearity,Z-scan,Nonlinear refractive index,Yb:YAG ceramics
更新于2025-09-16 10:30:52
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Use of high-power diode laser at 1060?nm for the treatment of vascular lesions
摘要： The use of 1060-nm wavelength light emitted from a high-power diode laser is a novel method for the removal of vascular lesions. Two Caucasian women with Fitzpatrick skin phototype II, who had various vascular lesions, were treated with a 1060-nm high-power diode laser, applying a fluence of 120 J/cm2 and a single pulse duration of 74 milliseconds. Immediate results were that the cherry angiomas became dark and a scab was formed (that remitted 2 weeks after treatment); the telangiectasias and venulectasias disappeared immediately. This technology has reported effective and safe results for removing different types of vascular lesions in the two patients treated. Side effects were those expected for this technique.
关键词： High-power diode laser,Nd: YAG,Venulectasias,Vascular lesions,Cherry angiomas,Telangiectasias
更新于2025-09-16 10:30:52
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Micro-channel fabrication on NiTi shape memory alloy substrate using Nd <sup>3+</sup> : YAG laser
摘要： Microchannel has been fabricated on NiTi shape memory alloy (SMA) sheet employing nanosecond Nd3+: YAG laser in open-air and underwater processing conditions. Microchannels were fabricated using three different laser wavelengths (1064, 532 and 355 nm) and scanning speeds (4, 10, 14 μm/s). A comparison of the effect of processing condition (open-air and underwater) and scanning speed on the kerf dimension has been examined. The scanning electron micrographs revealed no debris formation and no recast layer formation in underwater conditions whereas the surface irregularities were predominant in the open-air environment. Further, the influence of machining on NiTi in open-air and underwater was studied using UV-Vis spectroscopy. The austenitic phase attributed to shape memory characteristics was evident in processed material in comparison to unmachined material using the X-ray diffraction technique. In addition, differential scanning calorimetry demonstrated the phase transformation temperatures. The samples processed in open-air and underwater environment showed a significant shift in phase transformation temperatures. These laser-based processing techniques are highly useful in preserving smart material characteristics and fabrication of microchannels used in controlled volume drug delivery, microfluidic and waste or body heat-based actuated devices.
关键词： underwater,Nd3+: YAG,UV,NiTi,SMA,micro channeling,transformations,Laser
更新于2025-09-16 10:30:52
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Investigation of spectrally-dependent phonon relaxation mechanism in Yb:YAG gain media and its consequences for thin disk laser performance
摘要： Nonlinear phonon relaxation in Yb:YAG gain media has previously been investigated, and a hypothesis correlating photo-induced free electrons and heat generation in crystals pumped at a wavelength of 940 nm was established (Brandt et al 2011 Appl. Phys. B 102 765–8). Later, we demonstrated efficient suppression of nonlinear phonon relaxation by zero-phonon line (ZPL) pumping of Yb:YAG (969 nm). However, no hypothesis has yet been tested that correlates the heat load and the free electrons in Yb:YAG media. We investigate, both theoretically and experimentally, the behaviour of an Yb:YAG slab pumped by a high-power laser diode at a conventional broadband line (absorption maximum at 941 nm) and a ZPL (absorption maximum at 969 nm), and we compare the generated photocurrent, temperature, and absorbed pump power for those two pump wavelengths. Although the hypothesis established by Brandt et al (2011 Appl. Phys. B 102 765–8) was not confirmed, and the measured photocurrent was identical for the two pump wavelengths, our measurement contributes to the knowledge of the inner processes in Yb:YAG active media. In the following steps we characterized an Yb:YAG thin disk laser, measured the spectrally-resolved absorption and disk surface temperature, and optimised our predictive model of thin disk behaviour. All the experimental and theoretical results are reported.
关键词： numerical modelling,thin disk,thermal effects,Yb:YAG,photocurrent
更新于2025-09-16 10:30:52
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Enhanced topical cutaneous delivery of indocyanine green after various pretreatment regimens: comparison of fractional CO2 laser, fractional Er:YAG laser, microneedling, and radiofrequency
摘要： Different devices have been used to enhance topical drug delivery. Aim of this study was to compare the efficacy of different skin pretreatment regimens in topical drug delivery. In six ex vivo human abdominal skin samples, test regions were pretreated with fractional CO2 and Er:YAG laser (both 70 and 300 μm ablation depth, density of 5%), microneedling (500 μm needle length), fractional radiofrequency (ablation depth of ± 80–90 μm), and no pretreatment. The fluorescent agent indocyanine green (ICG) was applied. After 3 h, fluorescence intensity was measured at several depths using fluorescence photography. Significantly higher surface fluorescence intensities were found for pretreatment with fractional Er:YAG and CO2 laser and for microneedling vs. no pretreatment (p < 0.05), but not for radiofrequency vs. no pretreatment (p = 0.173). Fluorescence intensity was highest for the Er:YAG laser with 300 μm ablation depth (mean 38.89 arbitrary units; AU), followed by microneedling (33.02 AU) and CO2 laser with 300 μm ablation depth (26.25 AU). Pretreatment with both lasers with 300 μm ablation depth gave higher fluorescence intensity than with 70 μm ablation depth (Er:YAG laser, 21.65; CO2 laser, 18.50 AU). Mean fluorescence intensity for radiofrequency was 15.27 AU. Results were comparable at 200 and 400 μm depth in the skin. Pretreatment of the skin with fractional CO2 laser, fractional Er:YAG laser, and microneedling is effective for topical ICG delivery, while fractional radiofrequency is not. Deeper laser ablation results in improved ICG delivery. These findings may be relevant for the delivery of other drugs with comparable molecular properties.
关键词： Radiofrequency,Fractional laser,Er:YAG laser,Microneedling,Drug delivery,CO2 laser
更新于2025-09-16 10:30:52
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Objective assessment of YAG laser vitreolysis in patients with symptomatic vitreous floaters
摘要： Background: To objectively evaluate YAG laser vitreolysis for symptomatic vitreous floaters using color photo imaging. Methods: In this interventional and prospective study, 32 eyes of 32 patients with symptomatic vitreous floaters secondary to posterior vitreous detachment (PVD) were treated with a single session of yttrium aluminum garnet (YAG) laser. Primary outcomes were objective and subjective changes measured by masked grading of color fundus photographs and National Eye Institute Visual Functioning Questionnaire 25 (NEI VFQ-25), respectively. Secondary outcomes included Early Treatment Diabetic Retinopathy Study (ETDRS), best-corrected visual acuity (BCVA) and adverse events. Wilcoxon signed-rank test was used to analyze the results of the objective and subjective assessments at each time point. P < 0.05 was considered statistically significant. Results: Thirty-two patients (32 eyes; 13 men and 19 women) with symptomatic vitreous floaters were enrolled in this study (mean age: 59.4 years). All study patients were followed up for 6 months. Following the laser vitreolysis, there was a statistically significant improvement in both the near visual function (z = ? 2.97; p = 0.003; r = 0.633) and visual disturbance rate (z = ? 3.97; p < 0.001; r = 0.84). Distance visual function did not show statistically significant difference after the laser procedure (p = 1.00). Color fundus photograph did reveal vitreous opacity improvement over time in 93.7% of study eyes (partial improvement in 37.5% and total improvement in 56.2% of study eyes). During the follow-up period, recurrence of vitreous floaters, BCVA deterioration and adverse events were not observed. Conclusions: YAG laser vitreolysis decreased the amount of vitreous floaters opacities seen on color fundus imaging and improved related symptoms according to the NEI VFQ-25 responses.
关键词： Vitreous floaters,NEI VFQ-25 questionnaire,YAG laser,Vitreolysis,Color fundus photograph
更新于2025-09-16 10:30:52
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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) - Towards a kW-Class Picosecond Laser at 1 kHz
摘要： Secondary sources development such as X-rays for medical applications demand diode-pumped high-energy, high-power and high repetition rate picosecond lasers leading to a race to the kW milestone. Year after year, the pulse energy increased to few hundreds of millijoules at 1 kHz [1], but all the kW systems are based on the Yb:YAG thin disk technology which until now, to the best of our knowledge, has come short to deliver the full kilowatt level at 1 kHz. On the other side, cryogenically cooled bulk Yb:YAG amplifiers has shown its capabilities to reach 1 J at 500 Hz with 3.8 ps pulses [2]. Since two years, CELIA has launched new technology developments for a new system (HORIZON) aiming to reach 1 J, 1 kHz, 1 ps. We selected Yb:YAG crystal as laser gain medium since its thermal properties and its low quantum defect are suitable for high power laser generation. However, its narrow spectral bandwidth and its high saturation fluence impose large constraints on both the amplifier and compressor architectures. Cutting-edge technologies such as hypercompressor [3], divided pulse amplification [4], thin-disk and liquid-cooled disks are explored to address these limitations.
关键词： thin disk technology,cryogenically cooled bulk Yb:YAG amplifiers,high repetition rate,high-power,divided pulse amplification,hypercompressor,picosecond lasers,Yb:YAG,high-energy
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) - Temperature and Pumping Beam Radius Influence on Yb:YAG/Cr:YAG Microchip Laser Output
摘要： Miniature high peak power laser systems based on the microchip geometry are promising radiation sources for many applications, like micromanufacturing, remote sensing, data storage, LIBS, etc. The suitability and excellent performance of Yb:YAG/Cr:YAG micro-lasers were reported recently. This study follows our previous experiments and it is focused on investigation of the temperature and pumping beam radius influence on the output parameters of the longitudinally diode-pumped passively Q-switched Yb:YAG/Cr:YAG microchip laser. The goal was to reach as high as possible output energy for given pumping power. The tested microchip laser was based on monolith crystal (diameter 3 mm) which combines in one piece an active laser part (Yb:YAG crystal, 10 at.% Yb/Y, 3 mm long) and saturable absorber (Cr:YAG crystal, 1.36 mm long, initial transmission 90% @ 1.03 mm). The laser resonator pump mirror (HT for pump radiation, HR for generated radiation) was directly deposited on the Yb:YAG monolith part. The output coupler with reflection 55% @ 1.03 mm was placed on the Cr:YAG part. The microchip laser was placed in the temperature controlled cupreous holder inside vacuum chamber of the liquid nitrogen cryostat. For longitudinal pumping of Yb:YAG part, a fibre coupled (core diameter 400 mm, NA=0.22) laser diode was used. The laser diode was operating in pulsed regime (repetition rate 20 Hz, pulse length 3 ms, pumping power amplitude 33.6 W, operating wavelength 933 nm). Seven various pumping optics offering pumping beam waist radius wpmp (at 1/e2 of beam intensity) from 0.27 up to 1.05 mm were tested. The pulse duration, pulse energy, pulse build-up time, pulses repetition rate, and output beam divergence were measured in dependence on microchip temperature in range from 80 up to 350 K. It was found, that the pumping beam radius does not significantly influence on the pulse duration which was 1.5 ± 0.5 ns (FWHM). The single Q-switched pulse energy was increasing with the pumping beam radius up to wpmp=0.87 mm. The output energy was also possible to maximize by temperature tuning. The highest generated single Q-switched pulse energy (2.41 mJ) was obtained for pumping beam radius 0.87 mm at temperature 140 K for given pumping power. The corresponding peak power was 1.67 MW @ 1030 nm. The results showed that the temperature and pumping beam radius optimization can significantly improve the parameters of Q-switched pulses generated by Yb:YAG/Cr:YAG microchip laser.
关键词： Q-switched pulses,temperature influence,output energy,Yb:YAG/Cr:YAG microchip laser,pumping beam radius
更新于2025-09-12 10:27:22