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.

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.

Effect of open ultraviolet germicidal irradiation lamps on functionality of excimer lasers used in cornea surgery

We report on the impact of direct ultraviolet germicidal irradiation（UVGI）on reflective optics,used in the excimer laser system Allegretto Eye-Q.The aim of our work was to confirm our hypothesis based on long-rate observations of obtained anomalies in post-operative results that are attributed to degradation of reflective optics upon ultraviolet radiation.The presence of direct UVGI coupled with humidity in the operating environment caused merging anomalies and unwanted post-operative correction values.Ultraviolet-A radiation caused a similar effect on the reflective cover of the mirrors.

Surface Modification of Ceramic Materials Using Excimer Laser

Changes of surface morphology following XeCI excimer laser irradiation were investigated for three engineering ceramic materials (Al2O3, Al2O3-SiC nanocomposite and Si3N4). Al2O3 and AI2O3-SiC nanocomposite samples exhibit a smooth rapid melt layer on the surface, and the formation of the metastabfe γ-Al2Oa was observed. A silicon-rich layer on the surface was formed after laser irradiation of Si3N4. The toughness K1c of the materials was measured by the indentation fracture method. After laser irradiation, the toughness of Al2O3, Al2O3-SiC nanocomposite and Si3N4 was improved to various degrees: Al2O3-SiC nanocomposite, 60% (max.); AI203, 40% (max.); Si3N4, 12% (max.).

Ceramics Surface Modification by Excimer Laser Metal Coating

Thin metallic layers (~ 2 μm) of Ni were deposited on polycrystalline Al2O3. ZrO2 and (Ce-TZP)+Al2O3 ceramic substrates. and further irradiated with pulsed excimer (Xeno chloride) laser pulses. The laser energy density was varied from 0.21 to 0.81 J / cm2 to optimize bending strength. For ZrO2 ceramic, it was found that the strength increases from 530 to 753 MPa at 0.51 J / cm2 irradiation. For Al2O3 and (Ce-TZP)+ Al2O3 the fracture strength also increases in varying degree. The causes of strength increment were discussed.

LASER FLASH SPECTROSCOPY STUDIES OF PYRENE EXCIMER IN ACETONITRILE

Formation and decay processes of pyrene excimer in acetonitrile have been measured by laser flash spectroscopy at 475nm,and the dependence of λ_1+λ_2 on the pyrene concentration has also been measured at 290°K.On the basis of these measurements,six rate parameters which describe the behaviour of pyrene excimer system in acetonitrile solution have been evaluated.At 355 nm laser light irradiation,the ΔG of the pyrene excimer formation in acetonitrile is evaluated to be -30.18kJ/mol. This value is quite different from the corresponding ΔG in cyclohexane (-16.72kJ/mol).

Successful opening in-stent chronic total occlusion lesion of coronary artery by excimer laser coronary angioplasty

In percutaneous coronary intervention (PCI), chronic total occlusion (CTO) coronary artery disease still remains difficult to treat. One of the reasons for the failure is the hard of the CTO lesions that balloon is difficult to pass through or expand. Previous methods to deal with CTO lesions that cannot be passed by balloon, include selecting reinforced catheter (such as 5 in 6 guiding catheter, Guidzilla catheter, or Tornus microcatheter), guidewire extrusion or rotary grinding technology. In recent years, excimer laser coronary angioplasty (ELCA) has been gradually applied to CTO lesions. Using inert halide as the laser medium, ELCA emits a 308 nm high-intensity unidirectional light wave with absorption depth of only 50 μmL, resulting in less thermal effect and less damage to non-target lesions. In this paper, we will describe a successful PCI case of an in-stent CTO lesion using ELCA with long term coronary angiography follow-up.

Percutaneous recanalization of total saphenous vein graft occlusion with excimer laser treatment

Patients presenting with recurrence of anginal symptoms after saphenous vein bypass surgery pose an increasingly frequent challenge.In general,approximately 40%to 50%of saphenous vein graft(SVG)will become diseased or occluded within the first ten years after surgery.[1]Because adverse clinical outcomes,such as high restenosis rates and distal embolization,have been reported,percutaneous coronary intervention(PCI)for SVG is not recommended as a first-line strategy.[2]Distal embolization occurs in 2%–17%of patients despite advances in therapy,including the utilization of embolic protection device(EPD),which may lead to increased mortality at both short follow-up and midterm follow-up.[3]However,these patients often associated with inappropriate anatomic characteristics of native vessel intervention including calcification,tortuosity,abundant plaque burden,and complex chronic total occlusion(CTO)lesions.Moreover,repeat coronary bypass surgery is an option but is technically more demanding and is associated with a higher mortality.Therefore,it can sometimes result in SVG stenosis being the only intervention option.This is why the recanalization of SVG lesions,especially totally occluded lesions,remains one of the most challenging procedures in interventional cardiology.

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.

CLINICAL ANALYSIS OF EXCIMER LASER PHOTOREFRACTIVE KERATECTOMY FOR TREATMENT OF MYOPIA AND MYOPIC ASTIGMATISM

To evaluate the efficacy and accuracy of photorefractive keratectomy (PRK) for myopia and myopic astigmatism .SVS APEX excimer laser with a wave length of 193 nm(Sumit Technology Inc. Waltham, Mass, USA) was applied. 316 myopic eyes of 168 patients were treated with PRK between September, 1996 and October, 1997, and 260 eyes (84%) of 150 patients were followed for more than three months, including male 68(116 eyes, 401%) and female 82(144 eyes, 599%). The preoperative spherical equivalent refractive errors ranged from -125D to -1000 (mean -467163D), and astigmatism ranged from 0 to -200D (means -033045D). We divided the patients into two groups according to the referaction: group A (from -125D to -590D) and group B(from -600 to -1000D). The number of eyes in the two groups were 220 and 40 respectively. In group A, on the 10th day, 689% has the uncorrected visual acuity (UCVA) equal to or one line better or lower than the preoperative best corrected visual acuity (BCVA). In 1,3,6 and 12 months, 90 %, 96%, 95% and 94% had the UCVA equal to or one line better or lower than the preoperative BCVA respectively. In group B, on the 10 th day, in 1,3,6 and 12 months, UCVA equal to or one line better or lower than the preoperative BCVA occurred in 359%, 83%, 87%, 86%, and 84% of the cases respectively. Most of the haze showed 051 grades except 3 eyes with the haze of 2 grade in 3 or 6 months and it changed to 1 and 05 grade respectively within one year. In 10 days and 1,3,6,12 months postoperatively, the corneal haze was noted in 329%, 848%, 628%,90% and 28% of the treated eyes respectively. We found that 193 nm excimer laser PRK was a predictable, safe, stable, and effective refractive surgery for correcting myopia up to -1000D in Chinese patients, and the effect was better in myopia lower than -600D.

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.

Multiple excimer laser phototherapeutic keratectomies for Avellino corneal dystrophy:a case report

Dear Editor,I am Chihiro Koiwa,from the Department of Ophthalmology,Juntendo University Hospital.I am writing this letter to present a case of multiple excimer laser phototherapeutic keratectomies(PTKs)for Avellino corneal dystrophy(ACD).Corneal dystrophy is a common type of hereditary,noninflammatory,and bilateral corneal disorder that involves various pathological,histological,and clinical manifestations[1].Advanced molecular gene sequencing has identified specific mutations that are associated with most dystrophies of this type.ACD,also known as granular corneal dystrophy typeⅡ[2],is autosomal dominant and associated with the R124H mutation of the transforming growth factor beta-induced(TGFBI)gene and characterized by deposits consistent with both discrete granular and lattice corneal opacities[3-4].An analysis of the TGFBI gene is essential to differentiate ACD because heterozygous R124H mutation carriers have minimal corneal abnormalities,whereas homozygotes have severe visual impairment,starting from early childhood,and early postoperative recurrence of corneal opacity.

Surface Roughness Modification of Free Standing Single Crystal Silicon Microstructures Using KrF Excimer Laser Treatment for Mechanical Performance Improvement

Single crystal silicon freestanding structures for tensile and fatigue testing were treated with KrF excimer laser to improve surface roughness and accordingly mechanical performance. Sample thickness was 5 μm. Localized laser treatment was successful in eliminating the scallops developed during Bosch process and in reducing surface roughness. Harsh irradiation at laser energies up to 4 J/cm2 was only possible due to localized treatment without significant vibrations occurring on the freestanding samples that led to fracture in preliminary experiments at energies as low as 0.16 J/cm2. Finite element analysis was used to investigate the temperature distribution on the irradiated structures. Atomic force microscopy (AFM) and Raman spectroscopy were also used to assess surface roughness, crystallinity changes and surface stresses developing on surfaces subjected to perpendicular laser irradiation. At a high energy (3.2 J/cm2) the top surface showed a decrease of roughness compared to fabricated samples. Raman spectroscopy showed the dominance of crystalline silicon after laser irradiation. The effects of laser energy, number of

Consistent comparison of angle Kappa adjustment between Oculyzer and Topolyzer Vario topography guided LASIK for myopia by EX500 excimer laser

AIM： To evaluate and compare the uniformity of angle Kappa adjustment between Oculyzer and Topolyzer Vario topography guided ablation of laser in situ keratomileusis（LASIK） by EX500 excimer laser for myopia.METHODS： Totally 145 cases（290 consecutive eyes）with myopia received LASIK with a target of emmetropia. The ablation for 86 cases（172 eyes） was guided manually based on Oculyzer topography（study group）, while the ablation for 59 cases（118 eyes） was guided automatically by Topolyzer Vario topography（control group）. Measurement of adjustment values included data respectively in horizontal and vertical direction of cornea. RESULTS： Horizontally, synclastic adjustment between manually actual values（dx_（manu）） and Oculyzer topography guided data（dx_（ocu）） accounts 35.5% in study group, with mean dx_（manu）/dx_（ocu） of 0.78±0.48; while in control group, synclastic adjustment between automatically actual values（dx_（auto）） and Oculyzer topography data（dx_（ocu）） accounts 54.2%, with mean dx_（auto）/dx_（ocu） of 0.79±0.66. Vertically, synclastic adjustment between dy_（manu） and dy_（ocu） accounts 55.2% in study group, with mean dy_（manu）/dy_（ocu） of 0.61±0.42; while in control group, synclastic adjustment between dy_（auto） and dy_（ocu） accounts 66.1%, with mean dy_（auto）/dy_（ocu） of 0.66±0.65. There was no statistically significant difference in ratio of actual values/Oculyzer topography guided data in horizontal and vertical direction between two groups（P=0.951, 0.621）.CONCLUSION： There is high consistency in angle Kappa adjustment guided manually by Oculyzer and guided automatically by Topolyzer Vario topography during corneal refractive surgery by Wave Light EX500 excimer laser.

Comparison of clinical outcomes of deep anterior lamellar keratoplasty and excimer laser assisted anterior lamellar keratoplasty in keratoconus

AIM: To compare and evaluate the clinical outcomes of deep anterior lamellar keratoplasty(DALK) and excimer laser assisted anterior lamellar keratoplasty(ELLK) in eyes with keratoconus.METHODS: In this study, 57 eyes of 56 patients operated between 2013 to 2017 were included. Thirty-one eyes underwent big-bubble DALK and twenty-six eyes underwent ELLK. Preoperative and at control visits complete ophthalmic examination was performed. RESULTS: The mean patient age at the time of DALK surgery was 27 y and mean follow-up period was 21±5.4 mo. The mean patient age at the time of ELLK surgery was 27 y and mean follow-up period was 40±18 mo. Mean best spectacle corrected visual acuity(BSCVA) at postoperative period was significantly higher for DALK group(0.66±0.11) versus ELLK group(0.4±0.2)(P<0.05). Descemet's membrane microperforation was occurred in 7 patients in DALK group versus in 1 patient in ELLK group. In 4 eyes, interface irregularity was developed in ELLK group. None of the patients in follow-up had graft rejection in both groups.CONCLUSION: In ELLK group, complication rate is lower, the surgical technique is simpler, faster and safer and also ELLK requires less experience with respect to DALK. Further, DALK can be performed unless satisfactory visual acuity is achieved after ELLK.

The Characteristics of the Surface Topography of Excimer Laser Processed Al_2O_3 Ceramic

Surface of Al 2O 3 ceramic was processed by an excimer laser and the characteristics of topography were examined based on the application of the microelectromechanical system(MEMS). It is indicated that the statistic parameters of surface topography processed by the excimer laser have an obvious regularity. The arithmetic-mean value R a and the root-mean square value R q change with the changing of processing parameters in the same step and trend, and there is a quantitative relation between them.A simplified model is proposed for the excimer laser processing surface profile, whose results of the analysis and calculation agree basically with the experimental data. Furthermore,the surfaces processed by excimer laser are greatly flat. Skewness root-mean-square value Z· q changed little with the change of the technological parameters. The above characteristics depend on the processing principle of excimer laser, quite different from the cutting processing.

Phosphorus diffusion and activation in fluorine co-implanted germanium after excimer laser annealing

The diffusion and the activation of phosphorus in phosphorus and fluorine co-implanted Ge after being annealed by excimer laser are investigated.The results prove that the fluorine element plays an important role in suppressing phosphorus diffusion and enhancing phosphorus activation.Moreover,the rapid thermal annealing process is utilized to evaluate and verify the role of fluorine element.During the initial annealing of co-implanted Ge,it is easier to form high bonding energy FnVm clusters which can stabilize the excess vacancies,resulting in the reduced vacancy-assisted diffusion of phosphorus.The maximum activation concentration of about 4.4 ×10^(20) cm^(-3) with a reduced diffusion length and dopant loss is achieved in co-implanted Ge that is annealed at a tailored laser fluence of 175 mJ/cm^(2).The combination of excimer laser annealing and co-implantation technique provides a reference and guideline for high level n-type doping in Ge and is beneficial to its applications in the scaled Ge MOSFET technology and other devices.

Evaluation of Clinical Outcomes after LASIK for the Correction of Myopia Using the Advanced Customvue Excimer Laser Platform

-Purpose: To evaluate early visual, refractive and aberrometric outcomes after wave front-guided LASIK for the correction of low to moderate myopia and myopic astigmat is musing the excimer laser platform Advanced Custom Vue. Methods: A prospective, non-comparative study in 100 myopic eyes of 50 patients evaluating LASIK results over a period of 3 months. Main outcome variables included visual acuity, refraction, total higher-order aberrations (HOAs), spherical aberration (SA) and coma-like aberration. The surgery was performed using the VISX STAR S4 (Johnson and Johnson Vision) excimer laser and a wave front-guided ablation designed according to the iDesign aberrometer data (Johnson and Johnson Vision). Results: Mean preoperative sphere decreased from -4.07 ± 1.78 D to 0.32 ± 0.30 D at 3 months after surgery. Mean preoperative cylinder was reduced from -1.09 ± 0.88 D to -0.26 ± 0.28 D after the complete follow-up. Postoperative uncorrected distance visual acuity (UDVA) was 0.00 logMAR (20/20) or better in 100% of eyes, and 65.3% of eyes reached an UDVA of -0.20 logMAR (20/12.5) or better (p < 0.05). For a 6-mm pupil, the root mean square (RMS) for total ocular HOAs increased with surgery by 0.03 μm (p = 0.050), whereas the coma-like RMS increased by 0.05 μm (p < 0.001). The change in spherical aberration was +0.08 μm (p < 0.001). Conclusion: Wavefront-guided LASIK using the new generation excimer laser platform Advanced Custom Vue is safe and effective for treating myopia and myopic astigmatism, minimizing the postoperative level of HOAs.

Suicide after Excimer Laser Refractive Surgery: On the Importance of Matching Expectations

Background: Refractive surgery may change the individual life to the better largely eliminating the need for spectacles. However, expectations may vary and postoperative reality may come as a surprise. Aim: To emphasize the need for thorough alignment of expectations and options between surgeon and patient. Methods: A case is presented in which a successful refractive laser operation is a part of a trigger mechanism for a depressive episode leading to suicide. It emphasizes the crucial importance of constructive alignment of expectations between patient and treating physician prior to surgery. Results: The case presented outlines that ophthalmic surgery at the edge of high-tec with all its tempting features is also very attractive to individuals with very well defined and less flexible expectations. The possible irreversibility of some of the refractive surgery may force the patient postoperatively into a psychological corner, immobilizing him/her and restricting his/her options. Conclusions: High-tec operations dealing with one of the most elementary senses we have, vision, demand a thorough estimation of the patients profile prior to any surgery. Only matching expectations between the possible and desired outcome and reconfirmation of the match may reduce the risk of postoperative crisis which may carry a risk the patient’s life.

A HISTOPATHOLOGIC IMMUNOHISTOCHEMICAL AND ULTRASTRUCTURAL STUDY OF RABBIT CORNEA AFTER EXCIMER LASER PHOTOREFRACTIVE KERATECTOMY

Objective To evaluate the corneal healing of non-epuality diopter response histopathologically, immunohistochemically and ultrastructurally after excimer laser photorefractive keratectomy(PRK) with SVS APEX PLUS(Summit Technology Inc. USA) excimer laser, and the effects of corticosteroid on the healing. Methods PRK on 6 white rabbits(12 eyes) was performed on right eye or the rabbit for an attampted correction or -4.00 diopter and on left eye for an attempted correction of -8.00 diopter. The rabbits were divided into 2 groups randomly and each group included 6 eyes: Group FLM (3 rabbits, 6 eyes) and group CM (3 rabbits, 6 eyes). Fluoromethalone was given to group FLM,and chloromycetin to group CM. On 10d, 30d and 100d,the eyes of one rabbit in each group were enucleated randomly. Half of each cornea was prepared for electron microscope observation (SEM and TEM) and the rest embedded in OCT compound for immunohistochemical study to examine Ⅲ-C and FN. Results All eyes were reepithelialized within 3d after PRK. Subepithelial corneal haze was observed on 15d,which was dominant on 30 or 60d. On 100d postoperatively,corneal hazes of 11 eyes were grades 0 or 0.5,only 1 eye(the left eye or group CM) was denser haze (grade 1). On 3d postoperatively, one or two layers of corneal epithelial cell covered the ablation zone. On 30d after PRK,the epithelial cells showed hyperplastic changes. The cells were larger and increased from normal 5 or 6 layers to 7 or 8 layers of cells on l00d after PRK,epithelium was clear with more bright epithelium. Mi- croplicae and microvilli were less than before. The expression of Ⅲ-C and FN in group CM was significantly more evi- dent than that in group FLM. Conclusion The study show that despite recovery of a continuous and smooth epithelial layer and nearly normal corneal tissues on 100d after PRK,abnormalities of both epithelium and superficial stroma can be detected in the area of ablation. The ablation depth of stroma can influence the appearance of corneal haze af- ter PRK. The microplicae and microvilli of rabbit cornea epithelium become less after PRK,which can be one of cause leading to ocular dry sensation in some patients.