Conical Structures on Acrylic Intraocular Lens (IOLs) Materials after 193-nm Excimer Laser Ablation

Intraocular lens (IOLs) implants are synthetic lenses used to replace the natural lens of the eye and obtain optical reha- bilitation. The materials and methods of IOLs fabrication have been correlated with postoperative complications such as diffractive aberrations, capsular opacification or discoloration. Thus, several new materials and patterns are studied for the formation and etching of intraocular lenses (IOLs). In our work, we studied the use of UV laser as an alternative method to conventional surface shaping techniques for IOLs etching. Ablation experiments were conducted on hydrophobic acrylic IOLs by a commercial excimer laser system used in photorefractive surgery. The morphology of the irradiated area was observed by scanning electron microscopy (SEM) and a mathematical algorithm was used for SEM image processing. The effect of IOLs exposure to UV light before excimer laser irradiation was also examined, since natural ageing and cross-linking of IOLs material were reported. Conical structures were revealed after UV laser ablation and their population was increased with the number of laser pulses. Period distribution of cones was measured with the combination of image processing and a scanning algorithm which was developed for this reason. According to the graphs, the mean period and the distribution of the cones was depending of the number of irradiation pulses and the exposure to UV lamp before laser irradiation. Although a photochemical and a theoretically smooth-surface ablation mechanism is considered for the UV excimer laser interaction with polymers, surface conical-like abnormalities and thermal degradation of the lenses materials was observed.

Transperineal laser ablation of the prostate as a treatment for benign prostatic hyperplasia and prostate cancer: The results of a Delphi consensus project

Objective: To evaluate transperineal laser ablation (TPLA) with Echolaser® (Echolaser® TPLA, Elesta S.p.A., Calenzano, Italy) as a treatment for benign prostatic hyperplasia (BPH) and prostate cancer (PCa) using the Delphi consensus method.Methods: Italian and international experts on BPH and PCa participated in a collaborative consensus project. During two rounds, they expressed their opinions on Echolaser® TPLA for the treatment of BPH and PCa answering online questionnaires on indications, methodology, and potential complications of this technology. Level of agreement or disagreement to reach consensus was set at 75%. If the consensus was not achieved, questions were modified after each round. A final round was performed during an online meeting, in which results were discussed and finalized.Results: Thirty-two out of forty invited experts participated and consensus was reached on all topics. Agreement was achieved on recommending Echolaser® TPLA as a treatment of BPH in patients with ample range of prostate volume, from <40 mL (80%) to >80 mL (80%), comorbidities (100%), antiplatelet or anticoagulant treatment (96%), indwelling catheter (77%), and strong will of preserving ejaculatory function (100%). Majority of respondents agreed that Echolaser® TPLA is a potential option for the treatment of localized PCa (78%) and recommended it for low-risk PCa (90%). During the final round, experts concluded that it can be used for intermediate-risk PCa and it should be proposed as an effective alternative to radical prostatectomy for patients with strong will of avoiding urinary incontinence and sexual dysfunction. Almost all participants agreed that the transperineal approach of this organ-sparing technique is safer than transrectal and transurethral approaches typical of other techniques (97% of agreement among experts). Pre-procedural assessment, technical aspects, post-procedural catheterization, pharmacological therapy, and expected outcomes were discussed, leading to statements and recommendations.Conclusion: Echolaser® TPLA is a safe and effective procedure that treats BPH and localized PCa with satisfactory functional and sexual outcomes.

Effect of sample temperature on femtosecond laser ablation of copper

We conduct an experimental study supported by theoretical analysis of single laser ablating copper to investigate the interactions between laser and material at different sample temperatures,and predict the changes of ablation morphology and lattice temperature.For investigating the effect of sample temperature on femtosecond laser processing,we conduct experiments on and simulate the thermal behavior of femtosecond laser irradiating copper by using a two-temperature model.The simulation results show that both electron peak temperature and the relaxation time needed to reach equilibrium increase as initial sample temperature rises.When the sample temperature rises from 300 K to 600 K,the maximum lattice temperature of the copper surface increases by about 6500 K under femtosecond laser irradiation,and the ablation depth increases by 20%.The simulated ablation depths follow the same general trend as the experimental values.This work provides some theoretical basis and technical support for developing femtosecond laser processing in the field of metal materials.

Liquid vortexes and flows induced by femtosecond laser ablation in liquid governing formation of circular and crisscross LIPSS

Orientations of laser induced periodic surface structures(LIPSS)are usually considered to be governed by the laser polarization state.In this work,we unveil that fluid dynamics induced by femtosecond(fs)laser ablation in liquid(fs-LAL)can easily break this polarization restriction to produce irregular circular-LIPSS(CLIPPS)and crisscross-LIPSS(CCLIPSS).Fs laser ablation of silicon in water shows formation of diverse LIPSS depending on ablation conditions.At a high power of 700 mW(repetition rate of 100 kHz,pulse duration of 457 fs and wavelength of 1045 nm),single/twin CLIPSS are produced at the bottom of macropores of several microns in diameter due to the formation of strong liquid vortexes and occurrence of the vortex shedding effect.Theoretical simulations validate our speculation about the formation of liquid vortex with an ultrahigh static pressure,which can induce the microstructure trenches and cracks at the sidewalls for fs-LAL of Si and tungsten(W)in water,respectively.At a low power of 50 mW,weak liquid vortexes are produced,which only give birth to curved LIPSS in the valleys of grooves.Consequently,it is deduced that liquid vortex plays a crucial role in the formation of macropores.Mountain-like microstructures induce complex fluid dynamics which can cause the formation of CCLIPSS on them.It is believed that liquid vortexes and fluid dynamics presented in this work open up new possibilities to diversify the morphologies of LIPSS formed by fs-LAL.

Smaller Ge Quantum Dots Obtained by ArF Excimer Laser Annealing

Ge self-assembled quantum dots （SAQDs） are grown with a self-assembled UHV/CVD epitaxy system. Then, the as-grown Ge quantum dots are annealed by ArF excimer laser. In the ultra-shot laser pulse duration, -20ns, bulk diffusion is forbidden,and only surface diffusion occurs, resulting in a laser induced quantum dot （LIQD）. The diameter of the LIQD is 20-25nm which is much smaller than the as-grown dot and the LIQD has a higher density of about 6 ×10^10cm^-2. The surface morphology evolution is investigated by AFM.

Laser Ablation Atomic Beam Apparatus with Time-Sliced Velocity Map Imaging for Studying State-to-State Metal Reaction Dynamics

We report a newly constructed laser ablation crossed molecular beam apparatus, equipped with time-sliced velocity map imaging technique, to study state-to-state metal atom reaction dynamics. Supersonic metal atomic beam is generated by laser vaporization of metal rod, and free expansion design without gas flow channel has been employed to obtain a good quality of metal atomic beam. We have chosen the crossed-beam reaction Al＋O2 to test the performance of the new apparatus. Two-rotational-states selected AIO（X^2∑＋, v=0, N and N＋I4） products can be imaged via P（N） and R（N＋14） branches of the Av=l band at the same wavelength, during （1＋1） resonance-enhanced multi-photon ionization through the AIO（D2E＋） intermediate state. In our experiment at 244.145 nm for simultaneous transitions of P（15） and R（29） branch, two rings in slice image were clearly distinguishable, corresponding to the AiO（v=0, N=IS） and AIO（v=0, N=29） states respectively. The energy difference between the two rotational levels is 403 cm^-1. The success of two states resolved in our apparatus suggests a better collisional energy resolution compared with the recent research study [J. Chem. Phys. 140, 214304 （2014）].

Laser ablation of liver tumors:An ancillary technique,or an alternative to radiofrequency and microwave?

Radiofrequency ablation(RFA) is currently the most popular and used ablation modality for the treatment ofnon surgical patients with primary and secondary liver tumors, but in the last years microwave ablation(MWA) is being technically improved and widely rediscovered for clinical use. Laser thermal ablation(LTA) is by far less investigated and used than RFA and MWA, but the available data on its effectiveness and safety are quite good and comparable to those of RFA and MWA. All the three hyperthermia-based ablative techniques, when performed by skilled operators, can successfully treat all liver tumors eligible for thermal ablation, and to date in most centers of interventional oncology or interventional radiology the choice of the technique usually depends on the physician's preference and experience, or technical availability. However, RFA, MWA, and LTA have peculiar advantages and limitations that can make each of them more suitable than the other ones to treat patients and tumors with different characteristics. When all the three thermal ablation techniques are available, the choice among RFA, MWA, and LTA should be guided by their advantages and disadvantages, number, size, and location of the liver nodules, and cost-saving considerations, in order to give patients the best treatment option.

A New Synthetical Model of High-Power Pulsed Laser Ablation

We develop a new synthetical model of high-power pulsed laser ablation,which considers the dynamicabsorptance,vaporization,and plasma shielding.And the corresponding heat conduction equations with the initial andboundary conditions are given.The numerical solutions are obtained under the reasonable technical parameter condi-tions by taking YBa_2Cu_3O_7 target for example.The space-dependence and time-dependence of temperature in targetat a certain laser fluence are presented,then,the transmitted intensity through plasma plume,space-dependence oftemperature and ablation rate for different laser fluences are significantly analyzed.As a result,the satisfactorily goodagreement between our numerical results and experimental results indicates that the influences of the dynamic absorp-tance,vaporization,and plasma shielding cannot be neglected.Taking all the three mechanisms above simultaneouslyinto account for the first time,we cause the present model to be more practical.

Enhancement of laser ablation via interacting spatial double‐pulse effect

A novel spatial double-pulse laser ablation scheme is investigated to enhance the processing quality and efficiency fornanosecond laser ablation of silicon substrate. During the double-pulse laser ablation, two splitted laser beams simulta-neously irradiate on silicon surface at a tunable gap. The ablation quality and efficiency are evaluated by both scanning electron microscope and laser scanning confocal microscope. As tuning the gap distance, the ablation can be signifi-cantly enhanced if the spatial interaction between the two splitted laser pulses is optimized. The underlying physical mechanism for the interacting spatial double-pulse enhancement effect is attributed to the redistribution of the integratedenergy field, corresponding to the temperature field. This new method has great potential applications in laser microm-achining of functional devices at higher processing quality and faster speed.

In-situ surface decoration of RuO_(2) nanoparticles by laser ablation for improved oxygen evolution reaction activity in both acid and alkali solutions

Improving the OER activity of noble metal-based materials is of profound importance to minimize the usage of noble metals and lower the cost.Here,we report considerable improvement on the catalytic activity of RuO_(2) particles for OER in both alkali and acid environments.The RuO_(2) nanoparticles were treated with a method of pulse laser ablation.Numerous Ru and RuO_(2) clusters were generated at the surface of RuO_(2) nanoparticles after the laser ablation,forming a lychee-shaped morphology.The larger pulse energy RuO_(2) nanoparticles are treated with,the better the OER activity can be.DFT calculations shows that the surface tension induced by the lychee-shaped morphology benefits the OER performance.Our best sample gives an overpotential of 172 mV(at 10 mA cm^(-2))and a Tafel slope of 53.5 mV dec^(-1) in KOH,while an overpotential of 219 mV and a Tafel slope of 44.9 mV dec^(-1) in H_(2)SO_(4),which are of topclass results.This work may inspire a new way to develop high-performance electrocatalysts for OER.

GHz bursts in MHz burst(BiBurst) enabling high-speed femtosecond laser ablation of silicon due to prevention of air ionization

For the practical use of femtosecond laser ablation, inputs of higher laser intensity are preferred to attain high-throughput material removal. However, the use of higher laser intensities for increasing ablation rates can have detrimental effects on ablation quality due to excess heat generation and air ionization. This paper employs ablation using BiBurst femtosecond laser pulses, which consist of multiple bursts(2 and 5 bursts) at a repetition rate of 64 MHz, each containing multiple intra-pulses(2–20 pulses) at an ultrafast repetition rate of 4.88 GHz, to overcome these conflicting conditions. Ablation of silicon substrates using the BiBurst mode with 5 burst pulses and 20 intra-pulses successfully prevents air breakdown at packet energies higher than the pulse energy inducing the air ionization by the conventional femtosecond laser pulse irradiation(single-pulse mode). As a result, ablation speed can be enhanced by a factor of23 without deteriorating the ablation quality compared to that by the single-pulse mode ablation under the conditions where the air ionization is avoided.

Nickel-disilicide-assisted excimer laser crystallization of amorphous silicon

Polycrystalline silicon （poly-Si） thin film has been prepared by means of nickel-disilicide （NiSi2） assisted excimer laser crystallization （ELC）. The process to prepare a sample includes two steps. One step consists of the formation of NiSi2 precipitates by heat-treating the dehydrogenated amorphous silicon （a-Si） coated with a thin layer of Ni. And the other step consists of the formation of poly-Si grains by means of ELC. According to the test results of scanning electron microscopy （SEM）, another grain growth model named two-interface grain growth has been proposed to contrast with the conventional Ni-metal-induced lateral crystallization （Ni-MILC） model and the ELC model. That is, an additional grain growth interface other than that in conventional ELC is formed, which consists of NiSi2 precipitates and a-Si. The processes for grain growth according to various excimer laser energy densities delivered to the a-Si film have been discussed. It is discovered that grains with needle shape and most of a uniform orientation are formed which grow up with NiSi2 precipitates as seeds. The reason for the formation of such grains which are different from that of Ni-MILC without migration of Ni atoms is not clear. Our model and analysis point out a method to prepare grains with needle shape and mostly of a uniform orientation. If such grains are utilized to make thin-film transistor, its characteristics may be improved.

Disruption mitigation using laser ablation of high-Z impurities in HL-1M tokamak

A preliminary experiment triggering a plasma current quench by laser ablation of high-Z impurities has been performed in the HL-1M tokamak. The injection of impurities with higher electric charges into tokamak plasmas can increase the radiation cooling of the plasma. Resistive, highly radiating plasma formed prior to the thermal quench can dissipate both the thermal and magnetic energies, which is possibly a simple and potential approach to reducing significantly the plasma thermal energy and magnetic energy before a disruption thereby a safe plasma termination is obtained.

Comparative study of functional optical zone:small incision lenticule extraction versus femtosecond laser assisted excimer laser keratomileusis

AIM:To investigate the size of functional optical zone(FOZ)after small incision lenticule extraction(SMILE)versus femtosecond laser assisted excimer laser keratomileusis(FS-LASIK)for myopia correction and potential associated factors for FOZ.METHODS:A total of 133 patients who received corneal refractive surgery in our hospital between November 2018 and July 2021 were retrospectively enrolled.There were 63 patients(123 eyes)in SMILE group and 70patients(139 eyes)in FS-LASIK group.The size of FOZ was measured using Pentacam 3-dementional anterior segment analyzer before and 3mo after surgery,so as to analyze postoperative achieved functional optical zone(AFOZ)and its contributing parameters.RESULTS:When planned functional optical zone(PFOZ)was 6.5 mm for both groups,AFOZ was 1.45±0.27 and 1.67±0.25 mm smaller than preoperative FOZ in SMILE group and FS-LASIK group 3mo after surgery.AFOZ in SMILE group was significantly larger than that in FS-LASIK group(P<0.001).Variation of FOZ was negatively correlated with preoperative spherical equivalent(SE)and positively correlated with variation of mean keratometry value(△Km),variation of spherical aberration(△SA),and variation of Q-value(△Q,all P<0.001)in both groups.Multiple variable linear regression equations were△FOZ=1.354-0.1×pre-SE+0.336×△Q+1.462×△SA in SMILE group and△FOZ=1.512+0.137×△Q+0.468×△SA in FS-LASIK group.CONCLUSION:AFOZ is significantly smaller than preoperative FOZ in both SMILE and FS-LASIK groups.With the same PFOZ,larger AFOZ is achieved in SMILE group than in FS-LASIK group.

Excimer laser coronary atherectomy for a severe calcified coronary ostium lesion:A case report

BACKGROUND Percutaneous coronary intervention can be challenging for ostial coronary artery lesions due to calcium burden and elastic fiber content.Excimer laser coronary atherectomy(ELCA)is a less common treatment for severe calcified coronary ostium lesions.CASE SUMMARY An 81-year-old male presented to the Cardiology Department of Qingdao Municipal Hospital with a 1-year history of chest pain.Coronary angiography showed severe calcific stenosis(approximately 90%)in the right coronary artery ostium.The right coronary artery ostium was unable to be advanced using a 2.5 mm×12.0 mm balloon(NC Sprinter,Medtronic,United States)or dilated using a 2.0 mm×12.0 mm balloon(Sprinter,Medtronic,United States).The patient underwent successful ELCA and balloon dilation of the calcified coronary ostium lesion.CONCLUSION ELCA appears to be a safe and effective treatment for the management of severe calcified coronary ostium lesions.

Microwave Ablation versus Laser Ablation in Occluding Lateral Veins in Goats

Increasing number of endovenous techniques are available for the treatment of saphenous vein reflux and endovenous laser ablation（EVLA） is a frequently used method. A newly developed alternative, based on thermal therapy, is endovenous microwave ablation（EMA）. This study evaluated the effect of the two procedures, in terms of coagulation and histological changes, in occluding lateral veins in goats. Twelve animals were randomized into two group, with 6 treated with EMA（EMA group）, and the rest 6 with EVLA（EVLA group）. Results of coagulation, including coagulation, fibrinolysis and platelet activation, were assessed at three or four different time points： before, immediately after, 24 h（and 48 h） after ablation. The diameter change, a measure of efficacy, was ultrasonographically measured before and 1 month after the ablation. Histological changes were grossly and microscopically evaluated immediately, 1 and 3 month（s） after the ablation. The length of the ablated vein and preoperative average diameter were comparable between the two groups. In both EMA and EVLA groups, several coagulation parameters, fibrinolysis and platelet activation parameters only underwent slight changes. Ultrasound imaging displayed that the diameter reduction of the veins treated by EMA was significantly larger than by EVLA, in consistent with the results of macroscopic examination. Microscopic examination revealed necrosis and thickening of the vein wall, and occlusion of the lumen within 3 months after ablation in both EMA and EVLA groups. It is concluded that EMA is a minimally invasive therapy, which appears to be safe and effective for treatment of lateral veins in goats.

Understanding the effects of excimer laser treatment on corrosion behavior of biodegradable Mg-1Ca alloy in simulated body fluid

In this study,a KrF excimer laser was used to modify the biodegradable Mg-1Ca alloy and the time-evolution degradation behavior of the alloy before and after laser treatment was investigated in simulated body fluid(SBF)solution using immersion tests and electrochemical impedance spectroscopy(EIS).A 5μm melted layer with a homogeneous microstructure and an MgO film on the surface were achieved by laser radiation.Corrosion observations(hydrogen evolution,morphology and corrosion products)and EIS results revealed an improvement of corrosion resistance after laser treatment for 48 h.It was found a two-layer structure developed after 2 h immersion on both the untreated and laser-treated alloys,but the sequence of forming the two layers was opposite and greatly influenced by the laser-treated layer.The time-evolution corrosion processes on the untreated and laser-treated alloys were discussed,providing a better understanding of corrosion behavior of biodegradable Mg alloys modified by excimer laser.

Liver-directed therapies for liver metastases from neuroendocrine neoplasms:Can laser ablation play any role?

Aggressive cytoreduction can prolong survival in patients with unresectable liver metastases(LM)from neuroendocrine neoplasms(NEN),and minimally invasive,liver-directed therapies are gaining increasing interest.Catheter-based treatments are used in disseminated disease,whereas ablation techniques are usually indicated when the number of LM is limited.Although radiofrequency ablation(RFA)is by far the most used ablative technique,the goal of this opinion review is to explore the potential role of laser ablation(LA)in the treatment of LM from NEN.LA uses thinner needles than RFA,and this is an advantage when the tumors are in at-risk locations.Moreover,the multi-fiber technique enables the use of one to four laser fibers at once,and each fiber provides an almost spherical thermal lesion of 12-15 mm in diameter.Such a characteristic enables to tailor the size of each thermal lesion to the size of each tumor,sparing the liver parenchyma more than any other liver-directed therapy,and allowing for repeated treatments with low risk of liver failure.A recent retrospective study reporting the largest series of LM treated with LA documents both safety and effectiveness of LA,that can play a useful role in the multimodality approach to LM from NEN.

Optical near-field imaging and nanostructuring by means of laser ablation

In this review we consider the development of optical near-field imaging and nanostructuring by means of laser ablation since its early stages around the turn of the century.The interaction of short,intense laser pulses with nanoparticles on a surface leads to laterally tightly confined,strongly enhanced electromagnetic fields below and around the nano-objects,which can easily give rise to nanoablation.This effect can be exploited for structuring substrate surfaces on a length scale well below the diffraction limit,one to two orders smaller than the incident laser wavelength.We report on structure formation by the optical near field of both dielectric and metallic nano-objects,the latter allowing even stronger and more localized enhancement of the electromagnetic field due to the excitation of plasmon modes.Structuring with this method enables one to nanopattern large areas in a one-step parallel process with just one laser pulse irradiation,and in the course of time various improvements have been added to this technique,so that also more complex and even arbitrary structures can be produced by means of nanoablation.The near-field patterns generated on the surface can be read out with high resolution techniques like scanning electron microscopy and atomic force microscopy and provide thus a valuable tool-in conjunction with numerical calculations like finite difference time domain(FDTD)simulations-for a deeper understanding of the optical and plasmonic properties of nanostructures and their applications.

Reactions of Laser Ablation-magnesium Plasma with Methanol Clusters

The laser ablation-molecular beam（LA-MB） method is useful for studying the reactions of metal ions with molecular clusters. Reactions of magnesium plasma with methanol clusters were studied by using this method. A specially designed reaction cell was used as a fast flow reactor operated under thermal conditions, and the reaction products were measured with a time-of-flight（TOF） mass spectrometer. Surprisingly, several series of cluster ions with complex sizes and intensity distributions were obtained when the laser ablating was applied to different parts of the molecular beam. In the front part of the molecular beam, strong Mg^＋ （CH3OH）n（ n = 0-5） and weak H^＋ （CH3OH）n（ n = 0-5 ） cluster ions were observed with relatively small cluster sizes ; in the middle part of the molecular beam, the main cluster ions were H^＋ （ CH3OH）n （ n = 6-17 ） and H^＋（ H2O） 2 （ CH3OH）n（ n = 6-17 ） with a relatively large cluster size and a weak intensity; in the back part of the molecular beam, two new series of cluster ions, MgO^＋ （ H2O） （ CH3 OH）n（ n = 6-10 ） and MgOCH3^＋ （ CH3OH）n（ n = 6-10）, were obtained and accompanied by weak H^＋（CH3OH）n（n = 4-7） and H^＋（ H2O）2 （CH3OH）n（ n = 3-6）. The formation mechanisms and speed characteristics of the cluster ions are discussed in this article.