Excimer Laser System Research Articles

Correlation Analysis of Refractive and Visual Quality after Wavefront-Optimized Laser In Situ Keratomileusis for 50% and 100% Angle Kappa Compensation.

Purpose To analyze the distribution of the offset between the pupil center and the coaxially sighted corneal light reflex (P-Dist), the effects of 50% and 100% angle kappa adjustments on refractive and visual quality in patients with moderate myopia were investigated. Methods A randomly selected 254 patients (254 eyes) with moderate myopia who underwent femtosecond laser-combined LASIK were examined. During the operation, the P-Dist of the patients was recorded by the x- and y-axis eyeball-tracking adjustment program of the WaveLight Eagle Vision EX500 excimer laser system. Preoperatively and 3 months postoperatively, the WaveLight® ALLEGRO Topolyzer was used to measure the pupil size and center position, and the wavefront sensor was used to measure the wavefront aberrations. The visual function tester (OPTEC 6500) measured contrast sensitivity. Results The average P-Dist was 0.220 ± 0.102 mm. When the P-Dist >0.220 mm, the postoperative residual cylinder was 0.29 ± 0.34 D in the group with the 50% adjustment and 0.40 ± 0.32 D in the 100% group, which was significantly higher than the 50% group (P=0.036). The coma was 0.21 ± 0.17 μm in the 50% adjusted group and 0.34 ± 0.25 μm in the 100% group, which was significantly higher than that in the 50% group (P=0.021). At the 1.5 c/d spatial frequency, contrast sensitivity in the adjusted 100% group was significantly lower than that in the 50% group under visual glare conditions (P=0.039). Conclusion The postoperative visual acuity and spherical equivalent were not affected in the two groups. However, when P-Dist >0.220 mm, the residual astigmatism and coma were lower in the 50% group. Individualized operations for those with moderate myopia and large-angle kappa in which 100% adjustment is chosen may not result in a better visual quality effect than 50%.

Surface modification of SiOx film anodes by laser annealing and improvement of cyclability for lithium-ion batteries

SiOx (x = 0.66, 0.76 and 1.04) film anodes with the different oxygen content were prepared by radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) through adjusting SiH4/N2O (R) gas flow ration. The introduction of oxygen can alleviate volume expansion in the discharge/charge process at the expense of cyclic specific capacity. To obtain both higher capacity and cyclically stable SiOx film anodes, KrF excimer laser system operated at λ = 248 nm can induce to form nanoparticles on the surface of SiO0.76 film, which is related to the formation of solid electrolyte interphase (SEI) area during charge/discharge process. The SEI area becomes larger and mechanically robust with increase of laser energy density, which suppresses structural degeneration for giving lithium-ion battery longer cycle life. At the laser energy density of 266 mJ/cm2, SiO0.76 annealed film anode delivers capacity of 1731 mAh/g and capacity retention of 94.8% after 300 cycles, which are much higher than that of as-deposited anode. Increasing laser energy density to 433 mJ/cm2, SiO0.76 film anode shows higher capacity retention of 97.4% after 300 cycles.

Inscription of superimposed tilted fiber Bragg gratings

This study focuses on the tilted fiber Bragg gratings. The paper describes the method of their inscription into optical fiber using the Talbot interferometer and KrF excimer laser system. The method allows precise selection of the resonant wavelengths and tilt angles of the created structures in a wide range of values. In course of the study, an original method was proposed for inscription of a superposition comprising two structures being identical in parameters but having the opposite tilt angles of grating strokes relative to the optical fiber cross-section. The described method makes it possible to compensate the decrease in the reflective efficiency of fiber Bragg gratings with an increase in their tilt angle.

Laser ablation split-stream analysis of the Sm-Nd and U-Pb isotope compositions of monazite, titanite, and apatite – Improvements, potential reference materials, and application to the Archean Saglek Block gneisses

Continued improvements in both ICPMS (inductively-coupled plasma mass spectrometry) and laser ablation technologies are fueling advancements in accessory mineral investigations and their related isotope systems of interest, and are now being applied to a wide range of geological applications. In this contribution we present an updated methodology for laser ablation split-stream (LASS) analysis of the light rare earth element (LREE) enriched minerals monazite, titanite, and apatite for simultaneous analysis of the U-Th-Pb age (or trace element content) and the Sm-Nd isotope system. The data were collected with the current generation of high-sensitivity ICPMS and laser systems (ThermoFinnigan NeptunePlus MC-ICPMS and Element XR SF-ICPMS- coupled to a RESOlution 193 nm ArF excimer laser system). The increased sensitivity of these ICPMS instruments allows for improved spatial resolution and the ability to target minerals which previously contained insufficient concentrations of elements of interest (e.g., Sm-Nd in apatite), making their analysis difficult, if not impossible, using less sensitive instruments. Furthermore, the higher sensitivity allows less aggressive ablation parameters that facilitate thin section sampling and reduces inter-element and isotopic fractionation.To assess and improve the accuracy, precision, and efficiency of the technique, three new potential LASS reference materials (RMs) are evaluated for dual U-Pb and Sm-Nd analysis (Tory Hill apatite, Tory Hill titanite, and Steenskralkamp monazite). The homogeneity of these materials was first assessed using reconnaissance laser ablation analyses, with final characterization of U-Pb age and Sm-Nd isotope composition using isotope-dilution thermal ionization mass spectrometry (ID-TIMS). The precision and accuracy of the LASS method is explored using secondary mineral reference materials of known age and Sm-Nd isotope composition. The utility of the technique is evaluated with a case study of monazite and apatite from the Eoarchean Uivak Gneiss complex of Labrador, Canada. Finally, we suggest that there is a wide variety of geological applications for this methodology, such as multi-mineral detrital provenance, crustal growth, and petrogenic studies.

Analysis of ArF excimer laser system discharge characteristics in different buffer gases

Excimer laser is the current mainstream source of international semiconductor lithography. The stable operation of the laser system directly affects the working efficiency of the semiconductor lithography machine, so it is very important to optimize the laser system. The buffer gas commonly used in ArF excimer laser systems is He, Ne. In the early years, Shinjin Nagai and Mieko Ohwa have studied the output characteristics of the system when using He or Ne as a buffer gas from the aspect of pump efficiency and gain coefficient, and pointed out that using Ne instead of He has no obvious advantages in terms of efficiency. However, when Ne is used as the buffer gas, the reaction between Ne and electrons is more complicated. In addition to direct ionization and excitation reactions, it also contains a large amount of step ionization and secondary ionization, which releases free electrons. The stability of the system is improved, when Ne is used as the buffer gas. The ArF excimer laser system discharge characteristics in different buffer gases are analyzed based on fluid model in the paper. The role of photoionization is discussed. The simulation results show that the width of the electron depletion layer and the cathode sheath are both smaller, and the discharge stability is higher when Ne is used as the buffer gas. The expansion of the discharge region is accelerated and the threshold voltage of the discharge is reduced by adding Xe into Ne to trigger photoionization. The excimer laser discharge process is very complicated and is affected by many factors. Only two factors of the buffer gas and the photoionization process are studied in this paper. The simulation model will be extended from one-dimensional case to two-dimensional case in the future, and multiple physical factors of the ArF excimer laser system will be considered.

Clinical study on topography-guided laser ablation combined with accelerated corneal collagen cross-linking for early keratoconus

Objective: To study the safety and efficacy of topography-guided customized excimer laser subepithelial ablation combined with accelerated collagen cross-linking technique in treatment of early keratoconus. Methods: Ninteen patients(20 eyes) (13 males 14 eyes, and 6 females 6 eyes), aged 12 to 44 years (24.7±8.0) were diagnosed as keratoconus by three-dimensional corneal topography and tomography, clinical history and examinations, and classified as KC1~KC3. Based on the classical excimer laser subepithelial keratomileusis (LASEK) method, topography guided laser ablation was performed with an excimer laser system (WaveLight EX500). After laser ablation, the corneal stromal bed was immersed with 0.1% riboflavin for 10 minutes, and then was irradiated by ultraviolet light (Avedro KXL) at 30 mW/cm(2) for 4 minutes. All the patients were followed up for more than 12 months. The uncorrected visual acuity (UCVA), diopter, best corrected visual acuity (BSCVA), corneal topography, central corneal endothelial cell density (ECD), hexagonal cell percentage (HEX), coefficient of variation (CV) and other indicators were observed. For normal distribution variables, Dunnett-t test was used before and after operation, and Wilcoxon test was used for variables with abnormal distribution. And the complications were recorded. Results: There was no loss of BSCVA at 12 months postoperatively, 20% of the eyes had no change of BSCVA, and 15% of the eyes gained 1 line of BSCVA, 15% of the eyes gained 2 lines of BSCVA, 50% of the eyes gained 3 lines and more of BSCVA. There was no significant difference in UCVA, BSCVA, manifest refractive spherical equivalent (MRSE) and the cylinder at 3 months postoperatively (P>0.05). The BSCVA were significantly improved at 6 and 12 months postoperatively compared with those before operation (t=3.095, 3.079, <0.05). Although there was no significant difference in UCVA and MRSE, the cylinder was significantly reduced at 6 and 12 months postoperatively (t=-2.890, -2.435, P<0.05). Apex curvature (Kapex) and mean pupil power (MPP) within 4.5mm of central cornea decreased significantly (Z=-2.903, P<0.01; Z=-2.667, P<0.01). Even though the thinnest corneal thickness decreased from pre-operational (461.9±31.1) μm to post-operational (416.6±27.0) μm (Z=-3.059, P<0.01), the cornea became regular with keratometric asymmetry index of anterior corneal surface decreased (Z=-2.667, P<0.01). The corneal optical quality parameters were improved. There was no significant difference in ECD, HEX and CV at 12 months postoperatively (P>0.05). Twelve months after operation, grade 0, 0.5, 1 and 2 haze were seen on 20%, 55%, 20% and 5% corneas respectively. Conclusions: The topography guided excimer laser ablation combined with accelerated corneal collagen cross linking is safe and effective in treatment of early stage keratoconus. It can significantly improve corneal regularity while preventing keratoconus progression, so as to improve the best corrected visual acuity postoperatively. (Chin J Ophthalmol, 2019, 55: 904-910).

Transvenous excimer laser-assisted lead extraction of cardiac implantable electrical devices in the Japanese elderly population

BackgroundThe feasibility and safety of lead extraction of cardiac implantable electronic devices (CIEDs) in the elderly Asian population remain uncertain. We report the outcome and safety of transvenous excimer laser-assisted lead extraction of CIEDs in Japanese patients aged ≥80 years. MethodsConsecutive 235 patients (age 67±15 years, 167 male) undergoing lead extraction of CIED with an excimer laser system (Philips, Andover, MA, USA) were included. ResultsOf 235 consecutive patients, 51 (22%) were ≥80 years (age 86±5 years, 14 were aged ≥90 years; 42 had pacemakers, 3 had implantable cardioverter defibrillators, and 6 had cardiac resynchronization therapy devices). The median implant duration was 110±95 months. Patients aged ≥80 years had lower body mass index (BMI, 20.7±3.1kg/m2 vs. 22.6±3.4kg/m2, p<0.001), higher incidence of CIED infection (98% vs. 63%, p<0.010), and longer duration of hospitalization (31±17 days vs. 24 ± 31 days, p<0.001) than patients aged <80 years. There were no differences between the age groups in the rate of complete retrieval (94.1% vs. 95.1%, p=0.726) and major complications, including cardiac tamponade and cardiogenic shock (2.0% vs. 2.7%, p=1.000). ConclusionsExcimer laser-assisted lead extraction was safe and feasible in the Japanese elderly population with low BMI, despite the high likelihood of procedural complications. Early removal of infected CIEDs should be performed without delay in elderly Asian populations.

Stability of corneal topography and aberrometry after hyperopic laser in situ keratomileusis with a 500-Hz excimer laser platform: A 3-year follow-up study.

The aim of this study is to analyze the long-term stability of the corneal topography, the functional optical zone, and the refractive stability throughout 3 years following laser in situ keratomileusis surgery for hyperopia using a 500-Hz excimer laser system. This retrospective consecutive observational case series study comprised 66 eyes that underwent laser in situ keratomileusis to correct hyperopia with a postoperative follow-up of 3 years. Laser in situ keratomileusis procedures were performed using the SCHWIND Amaris 500-Hz excimer laser. Main outcomes measured were stability of the functional optical zone at corneal topography and corneal aberrometry. Statistically significant differences were found in simulated keratometry (K2 (steep meridian) and Km (mean keratometry)) between 3 and 36 months postoperatively (p ⩽ 0.01); these differences disappeared at 12 and 36 months (p ⩾ 0.18). No statistically significant changes were observed in the horizontal and vertical diameter of the functional optical zone throughout the whole follow-up (p ⩾ 0.07). A statistically significant difference was found in the spherical aberration between 3 and 36 months (p = 0.02); this difference disappeared when compared between 12 and 36 months (p = 0.72). Statistically significant correlations were detected between the vertical functional optical zone and coma root mean square (r = -0.510, p < 0.01) and between the vertical functional optical zone and spherical aberration (r = 0.441, p = 0.02) 36 months after surgery. Following 3 years of hyperopic laser in situ keratomileusis with a 500-Hz Amaris excimer laser, keratometry, functional optical zone, and corneal aberrations remain stable from 1 year after surgery. Topographical regression is not observed in hyperopic laser in situ keratomileusis with this excimer laser technology from 1 year after surgery.

Corneal Endothelial Cell Changes after Photorefractive Keratectomy for Low to Moderate Myopia With and Without Mitomycin-C

AbstractBackground: Mitomycin-C was suggested for application during surface ablation procedures to reduce post-operative haze formation. It can effectively reduce haze formation and hence, improve the predictability of visual outcomes following refractive surgery. Despite these advantages, MMC can po-tentially damage all three main corneal cell types including epithelial (differentiated epithelium and limbal cells), stromal (keratocytes), and endothelial cells.Aim of Study: To investigate the croneal endothelial cell changes after Photorefractive Keratectomy (PRK) with and without Mitomycin-C 0.02% for low to moderate myopia.Patient and Methods: This prospective, randomized, comparative study included 60 eyes of 30 patients who were chosen from Ophthalmology Clinic at Tanta University Hos-pital and Shorouk Laser Vision Correction Centre for 6 month from December 2017 to May 2018 and scheduled for Photo-refractive Keratectomy (PRK) using193nm wavelength exci-mer laser system Allegretto EX500, (Wave Light Technologie., USA). These patients were randomly divided into two groups. Group (A) were scheduled for (PRK) with adjunctive mito-mycin-C 0.02% and patients of Group (B) were scheduled for (PRK) without mitomycin-C. Informed consents were obtained from all study participants.Results: In Group A the mean Endothelial Cell Density (ECD) was 2891.61±272.41 and at three months after surgery was 28 13.04±276.55cells/mm2 (p=0.289), pre-operative mean of Coefficient of Variation (CV) was 34.87±4.37 and post-operatively was 34.70±4.06 (p=0.877), the pre-operative mean of Central Corneal Thickness (CCT) was 523.00±26.14 m and 467.36±40.61 m post-operatively (p=0.001), the mean of hexagonality pre-operatively was 64.26±8.64% and 59.96± 8.15% post-operatively (p=0.059) which was statistically insignificant. In Group B the mean Endothelial Cell Density was (ECD) 2874.50±314.48 and at three months after surgery was 2777.23±302.44cells/mm2 (p=0.227), pre-operative mean of Coefficient of Variation (CV) was 33.49±4.98 and post-operatively 33.55±4.10 (p=0.962), pre-operative mean of central corneal thickness was 538.03±26.03 and 484.50±20.55 post-operatively (p=0.001), the mean of hexagonality pre-operatively was 63.00±7.74 and 61.43±7.29% post-operatively (p=0.423).Conclusions: There's no significant effect on endothelium in patients underwent to PRK in low to moderate myopia with or without mitomycin-C. We can't judge the same results for patients with high myopia because the ablation depth will be more and theoretically the diffusion of mitomycin-C to en-dothelium would affect its function or count.

Excimer Laser Correction of Myopia Using Aspheric Technology. Literature Review

The article presents a literature review of scientific sources on the use of aspheric technology for the correction of refractive errors at the present stage of development of excimer laser surgery. The article highlights the pressing challenge of developing algorithms that improve quality indicators, maintaining subtle visual functions (low-contrast visual acuity, visual acuity in various illuminating conditions) after excimer laser correction of ametropy. The literature data on the etiology of visual acuity reduction after refractive operations are given. Special consideration is given to the description of asphericity indicators by the researchers, the importance of influence of the indicators on the qualitative characteristics of vision. The mechanism of influence of the modified aberration balance of the cornea after refractive interventions on the indicators of spatial-contrasting characteristics of vision in refractive patients is clarified; the importance of evaluating these indicators before and after refractive surgeries is emphasized. The types of aspherical ablation algorithms used in modern, both foreign and domestic, excimer laser systems, and their differences are described. Advantages and disadvantages of the aspherical algorithms used have been analyzed, historical evolution of the software that was developed and introduced into the new excimer laser systems for aspherical operations has been traced. Fundamental difference between aspheric ablation optimized with respect to wavefront with average asphericity index, introduced by the manufacturer of the facility, and the algorithm, where aspheric ablation is performed with personalized Q-factor, which can be controlled by the surgeon himself, is presented in detail. The problem of developing optimized technology of aspheric ablation algorithm in correcting myopia due to the existence of restrictions on the use of aspheric techniques on domestic “Microscan-VIZUM” excimer laser unit is emphasized.

Laser Surface Hardening of Gun Metal Alloys.

The effect of laser irradiation with different numbers of laser shots on the microstructure, the surface, and the hardness of gun metal alloy was studied by a KrF pulsed excimer laser system, X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and Vickers hardness test. The influence of 100–500 laser shots was irradiated on the surface hardness profile and on the microstructure of gunmetal alloy. XRD results showed the maximum 2θ shift, the maximum full width of half maximum FWHM, the maximum dislocation density, and the minimum crystallite size for the sample irradiated with 300 laser shots. The hardness was measured in three different regions at the laser irradiated spot, and it was found that maximum hardness was present at the heat affected zone for all samples. The hardness value of the un-irradiated sample of gun metal was 180, and the value increased up to 237 by raising the number of laser shots up to 300. The peak value of surface hardness of the laser treated sample was 32% higher than the un-irradiated sample. The Raman shift of the un-exposed sample was 605 cm−1 and shifted to a higher value of wave number at 635 cm−1 at 300 laser shots. The hardness value was decreased by further increasing the number of laser shots up to 500. The samples irradiated with 400 and 500 laser shots exhibited smaller hardness and dislocation defect density, which was assigned to possible annealing caused by irradiation.

Сравнительная оценка клинико-функциональных результатов операции ФемтоЛАЗИК, выполненной на различных эксимерлазерных установках, у пациентов с миопией слабой и средней степеней

Purpose. To evaluate visual and refractive results of FemtoLASIK using the WaveLight EX 500 and Microscan Visum excimer laser systems in patients with low to moderate myopia. Material and methods. This study was performed in 62 eyes of 62 patients with low to moderate myopia operated according to the FemtoLASIK technique using the different excimer lasers WaveLight EX 500 (USA) and Microscan Visum (Russia). All patients underwent a complete ophthalmological examination before the laser refractive surgery, on the 1st day and 1 month after the FemtoLASIK. The results are presented as Me (Q25; Q75). Results. Postoperatively the uncorrected distance visual acuity (UDVA) increased from 0.05 (0.04; 0.10) to 1.00 (1.00; 1.00) (p 0.05), the safety index was 1.00 (1.00; 1.00) and 1.00 (1.00; 1.00), respectively (p>0.05). Visual and refractive results showed no statistically significant difference between the two groups (p>0.05). The ablation depth was higher in the ≪Microscan Visum≫ group compared with the ≪WaveLight EX 500≫ group. Conclusions. 1. The conventional FemtoLASIK procedure using the WaveLight EX 500 and Microscan Visum excimer lasers, is an effective and safe method for low to moderate myopia correction. There is no statistically significant difference between two algorithms (p>0.05). 2. It is necessary to improve the standard ablation algorithm on the Microscan Visum excimer laser platform to reduce the ablation depth.

Effect of ArF excimer laser annealing on morphology and surface plasmon resonance properties of Ag nanoparticles

Ag nanoparticles were obtained in AZO/Ag and AZO/Ag/AZO films by magnetron sputtering method at room temperature. These as-deposited films are then annealed by ArF excimer laser system operated at λ = 193 nm. The effect of two different laser annealing processes on surface plasmon resonance (SPR) of Ag particles and photoelectric properties of these films can be discussed detailedly. AZO film substrates where the thermally active surface diffusion of Ag occurs play an important role in determining the morphologies of Ag particles. Ag films irradiated directly by laser annealing in AZO/Ag films tend to form spherical particles, while Ag films deposited on laser-irradiated AZO film substrates are likely to form irregular long particles. The results show that irregular long Ag particles can be obtained on AZO films with small and dense grains as nucleation centers induced by high laser energy densities, which can exhibit redshift of SPR peaks and optimize photoelectric properties. The SPR peak of irregular long Ag particles based on laser-irradiated AZO substrate can reach to 750 nm with an optical average transmittance of 83% and a $$ R_{\text{S}} $$ value of 16 Ω/sq at a laser energy density of 250 mJ/cm2.

LA-ICP-MS analyses of Fe-rich alloys: quantification of matrix effects for 193 nm excimer laser systems

The use of silicate calibrants for ns LA-ICP-MS analyses of Fe-based samples results in significant matrix effects. The magnitude of these effects, defined by the fractionation index or Fi, is a function of elemental volatility. Using the dependency of the Fi with elemental volatility a predictive model was developed to correct for these effects.

Outcomes of Wavefront-Optimized Laser-Assisted In-Situ Keratomileusis and Photorefractive Keratectomy for correction of Myopia and Myopic Astigmatism over One Year Follow-Up

Background:Laser corneal refractive surgery suits, technology and nomograms are improving with time. This may improve the refractive and visual outcomes of the patients.Objectives:To evaluate the safety, efficacy, stability, and predictability of wavefront-optimized photorefractive keratectomy and Laser-assisted in-situ keratomileusis in patients with myopia and myopic astigmatism over 1-year using WaveLight® EX500 Excimer Laser machine.Methods:In this prospective cohort study, refractive and visual outcomes in 596 eyes (365 patients), either having myopia or myopic astigmatism were assessed. Patients were divided into Two groups: 1) Patients who underwent PRK (53 eyes have myopia and 217 eyes have myopic astigmatism), 2) Patients who underwent LASIK (53 eyes have myopia and 273 eyes have myopic astigmatism).Results:At 12 months postoperatively 94.3% of the myopic patients reached their preoperative best corrected distance visual acuity at the final one year follow up visit post PRK and LASIK. In patients with myopic astigmatism who underwent LASIK and PRK, 95.2%, and 96.3% of the patients reached their preoperative best corrected distance visual acuity at the final one year follow up visit post LASIK and PRK, respectively. The efficacy and safety indices were 1.00 or more for all groups with no eye lost any line of best corrected distance visual acuity.Conclusion:Our study results confirm the excellent efficacy, safety, good predictability and stability of myopia / myopic astigmatism correction by either wavefront- optimized LASIK or PRK over 1-year follow-up without significant differences between them using the WaveLight® EX500 excimer laser system.

Bragg Gratings Inscription in TS-Doped PMMA POF by Using 248-nm KrF Pulses

We demonstrate the Bragg gratings inscription in the 850-nm spectral region by using trans-4-stilbenemethanol-doped poly methyl methacrylate step-index optical fiber and a 248-nm krypton fluoride (KrF) excimer laser system. The gratings inscription only takes 0.4 s. A detailed study of the grating fabrication process using different pulse repetition rates is also reported. In addition, temperature, humidity, and strain sensitivities are measured to demonstrate the potentiality of these components for different sensing applications.

Inscription and investigation of the spectral characteristics of chirped fiber Bragg gratings

The results of investigations of the spectral characteristics of chirped fiber Bragg gratings induced in an optical fiber using a Talbot interferometer and a KrF excimer laser system of the master oscillator–power amplifier type with enhanced coherence are presented. Dependences of the full width of the reflection spectrum at half maximum and the reflectivity of chirped fiber Bragg gratings on their length are obtained and analyzed. Through the inscription of seven superimposed chirped fiber Bragg gratings, a diffraction structure with a spectral width of 32 nm was obtained. In addition, a chirped fiber Bragg grating whose spectral response shape is almost rectangular is presented.

Fabrication and Characterization of Bragg Grating in CYTOP POF at 600-nm Wavelength

We demonstrate Bragg grating inscription in commercial CYTOP POF at a wavelength of 600nm using a 248nm krypton fluoride excimer laser system with a repetition rate of 40 Hz and average pulse energy of 0.60 0.02mJ during 60 min. Experimental characterization of the Bragg grating is performed under different conditions, where the temperature and strain sensitivities were accurately measured to define potential sensing and optical communication applications. Furthermore, different humidity conditions were experimentally tested, and it was proved CYTOP POF as a good candidate for sensing applications under humidity change environment.

High-speed recording of thermal load during laser trans-epithelial corneal refractive surgery using a 750 Hz ablation system

PurposeTo evaluate the temperature rise of human cornea during trans-epithelial photorefractive keratectomy (trans-PRK) with a 750Hz excimer laser employing Intelligent Thermal Effect Control (ITEC) software. MethodsIn this observational case series, trans-PRK ablation was performed on 5 eyes of 3 patients using an aspheric profile of a 750Hz excimer laser system. A high-resolution infrared camera with a frame-rate of 350 images per second was used to determine the corneal surface temperature. Images were taken sequentially, starting a few seconds prior to and ending a few seconds after the ablation. The maximum temperature of any pixel of a given image were recorded and graphed against time. ResultsThe baseline ocular surface temperature, immediately prior to the beginning of excimer laser, ranged from 32 to 34.9°C. The maximum ocular surface temperature until the epithelium was ablated ranged from 35.2 to 39.7°C. The maximum ocular surface temperature during stromal ablation with high and low fluence laser ranged from 32.9 to 36.5 and from 34.4 to 37.7°C respectively. ConclusionThe ITEC software is effective in controlling the maximum temperature rise during laser ablation in the extremely challenging situation of trans-PRK involving high ablation volumes of almost 6000nl, potentially improving the outcomes. The ITEC system limited the maximum temperature to 39.7°C in the epithelium, and 37.7°C in the stroma. The epithelial temperature was always higher than stromal temperature (regardless of high or low fluence irradiation). Safety limit of 40°C found in the literature was never reached.

Inscription and visualization of tilted fiber Bragg gratings

In this work the inscription and investigation of tilted fiber Bragg gratings induced in a single-mode isotropic optical fiber with increased photorefractivity are demonstrated. Using the Talbot interferometer and the KrF excimer laser system, tilted fiber Bragg gratings with different angles were fabricated, the spectra of the formed diffraction structures were analyzed, and their photographic images were taken with a confocal laser scanning fluorescence microscope in transmitted light. The calculated dependence of the tilt angle of tilted fiber Bragg gratings fabricated in the Talbot interferometer on the angle between the interference fringes created in the interferometer and the cross section of the optical fiber is experimentally verified.