Laser Radiation Research Articles

Photobiomodulation Effect of Different Diode Wavelengths on the Proliferation of Human Buccal Fat Pad Mesenchymal Cells

This study aimed to determine the most effective wavelength for the proliferation of Human Buccal Fat Pad Mesenchymal Stem Cells (BFPMSCs) in cell culture. These cells can be used for different purposes such as regenerative periodontal procedures. Materials and Methods: The wells containing BFPMSCs were subjected to laser irradiation at 635, 660, 808, and 980 nm wavelengths with 1, 1.5, 2.5, and 4 J/cm2 energy densities. Cell proliferation and viability were evaluated after 1, 3, and 5 days with the methyl thiazolyl tetrazolium (MTT) assay. Result: The proliferation rate of human Buccal Fat Pad Mesenchymal Cells (BFPMSCs) was increased on the first and third days at a wavelength of 808 nm and day five at a wavelength of 980 nm in comparison to the control group. Our findings distinguished that PBMT with 635, 660, 808, and 980 nm wavelengths increased the proliferation of BFPMSCs. Conclusion: The best laser radiation setting, which led to the highest proliferation rate of the cells, included a wavelength of 808 nm with 2.5 J/cm2 energy density.

Study of Photodegradation of Thiazion Dye Methylene Blue under Exposure to a Laser for Photodynamic Therapy

Purpose. To study the process of photodegradation of methylene blue under the influence of laser radiation with a wavelength of 660 nm, used for photodynamic therapy installations, for the formation of reactive oxygen species, in particular short-lived hydroxyl radicals, using electron paramagnetic resonance (EPR) spectroscopy.Methods. The residual concentration of methylene blue during photodegradation was determined using an HR2000 spectrometer. The formation of hydroxyl groups was detected using an EPR spectrometer SPINSCAN X.Results. Analysis of data on the photodegradation of methylene blue shows that under the influence of laser radiation with a wavelength of 660 nm, the structure of methylene blue is destroyed, manifested in the gradual discoloration of the dye solution. When trypaflavin is added to the solution, the rate of photodegradation of methylene blue slows down significantly. Analysis of ESR spectroscopy data shows that when methylene blue is exposed to a red laser, (OH’) radicals begin to intensively form in the solution. Their content increases significantly with increasing irradiation power.Conclusion. Irradiation of an aqueous solution of the thiazion dye methylene blue by a laser source with a power of 0.3÷1 W and a wavelength of 660 nm leads to its active photodegradation. The addition of trypaflavin leads to a slowdown in the process of photodegradation of methylene blue when irradiated with red light due to the consumption of part of the generated oxygen-containing radicals for the degradation of trypaflavin. According to EPR spectroscopy data using DMPO spin traps, it has been proven that when methylene blue is irradiated with a red laser, active formation of hydroxyl OH' radicals occurs. It was found that with increasing laser radiation intensity, the amount of generated hydroxyl radicals (OH') increases significantly. The presented results may contribute to the development of effective photosensitizers for photodynamic therapy of tumor tumors.

Fabrication of SnS (NF)/Ag (NW) composite and investigation of its photothermal properties in destroying HeLa cell line

The photothermal effect is a special type of photoactivation based on the non-radiative conversion of absorbed electromagnetic energy, increases the body's temperature. One of the important applications of photothermal is photothermal therapy (PTT) to destroy cancer cells. In this article, SnS nanoflowers (NF) and Ag nanowires (NW) were synthesized by solvothermal method. They were composited together with different mass ratios and characterized by XRD, SEM, and EDS analysis. The optical band gap was calculated 2.62 eV using UV–vis spectrum. The photothermal properties of these nanoparticles were investigated using an 808 nm laser at different concentrations and different laser powers. SnS/Ag composites with different mass ratios were tested and the highest temperature increase of 42.8 °C was observed for a ratio of 17:1 under 1 W/cm2 laser radiation. The photothermal conversion efficiency of SnS (NF) and its composite with Ag (NW) was calculated as 56.32 % and 67.7 %, respectively. The toxicity effect of nanoparticles and laser on HeLa cancer cells was investigated by MTT method. It was observed that during 5 and 10 min of laser irradiation, with the presence of SnS (NF), 94.7 % and 95.7 %, and for its composite with Ag(NW), respectively, 95 % and 95.8 % of HeLa cancer cells were destroyed.

Laser Engineering Nanocarbon Phases within Diamond for Science and Electronics.

Diamond, as the densest allotrope of carbon, displays a range of exemplary material properties that are attractive from a device perspective. Despite diamond displaying high carbon-carbon bond strength, ultrashort (femtosecond) pulse laser radiation can provide sufficient energy for highly localized internal breakdown of the diamond lattice. The less-dense carbon structures generated on lattice breakdown are subject to significant pressure from the surrounding diamond matrix, leading to highly unusual formation conditions. By tailoring the laser dose delivered to the diamond, it is shown that it is possible to create continuously modified internal tracks with varying electrical conduction properties. In addition to the widely reported conducting tracks, conditions leading to semiconducting and insulating written tracks have been identified. High-resolution transmission electron microscopy (HRTEM) is used to visualize the structural transformations taking place and provide insight into the different conduction regimes. The HRTEM reveals a highly diverse range of nanocarbon structures are generated by the laser irradiation, including many signatures for different so-called diaphite complexes, which have been seen in meteorite samples and seem to mediate the laser-induced breakdown of the diamond. This work offers insight into possible formation methods for the diamond and related nanocarbon phases found in meteorites.

Properties of AlxGa1-xAs grown from a mixed Ga-Bi melt.

Thick smoothly graded AlxGa1-xAs layers (50-100µm) are used in light-emitting diode structures and also for creation of high-power photovoltaic converters with side-input of laser radiation. To achieve the required thickness of the AlxGa1-xAs layer the high temperature LPE growth technique is required. However high epitaxial temperature increases the unintentional doping level. Epitaxy from mixed Ga-Bi melts was investigated as a way to solve this problem. It was found that for growing relatively thick AlxGa1-xAs layers, it is expedient to use Ga-Bi melts with 20 at% or less bismuth content. SIMS and Hall characterization of AlxGa1-xAs layers revealed that the growth of AlxGa1-xAs from mixed Ga-Bi melts reduces the background doping level (including carbon) and influences the native defect formation keeping the n-type conductivity. This effect is explained by the changes of the group III and V elements concentrations in the melt as well as Bi incorporation in the lattice.

Radioreparative Effect of Diode Laser on Leukopoiesis Recovery: A Pilot Study.

The aim of the present study was to investigate the effect of laser therapy on leukopoiesis recovery after irradiation with ionizing radiation. A dose of ionizing radiation was used that induced the hematological form of radiation sickness, reducing the number of blood cells. Subsequently, mice were treated with non-ionizing laser radiation. Based on the examination of the peripheral blood, the study found that laser therapy significantly impacted the number of eosinophils and basophils two weeks after irradiation. Laser therapy also led to the faster reparation of the lymphocyte lineage of white blood cells (WBCs). The research showed that the examined therapeutic laser had a long-term radioreparative effect on gamma-irradiated mice, improving the absolute counts of different lines of WBCs. The results of this study could have implications for the treatment of radiation sickness in humans.

The influence of heating on the appearance of polarization singularities during the self-action of a Gaussian beam in the isotropic phase of a nematic liquid crystal in the pre-transition temperature region

Heating of the medium occurs during the self-action of elliptically polarized light in the isotropic phase of a nematic liquid crystal near the transition temperature to the mesophase. We studied the influence of heating of the medium, on the propagation modes of laser radiation and the dynamics of the formation of singularity lines of circular polarization in the cross sections of the beam, which is closely related to the multifocal structure of the electric field. It is shown that an increase in the incident radiation intensity leads to a decrease in distance from the front end of the cylindrical cuvette to the beam cross section, containing the primary (brightest and most stable) polarization singularity lines, as well as in the radius of the circle they form. The range of parameters of the incident radiation and medium at which the multifocal structure of the electric field of the propagating beam is formed, as well as the intensity threshold values at which it appears, decreases with the growth of the thermal conductivity coefficient of the liquid crystal.

Different wavelengths of laser: are they significant for treatment of denture stomatitis?: an in-vitro study

BackgroundDenture stomatitis (DS) is an inflammatory disorder that affects the mucosal surface underneath the dentures and frequently causes oral mucosal irritation, discomfort, and altered taste perception, which prevents people from consuming enough nutrients. One of the main causes of DS is an overgrowth of the fungus Candida albicans (C. albicans). A possible alternative treatment for Candida infections is thought to be laser therapy. The aim of this study was to evaluate how different wavelengths of laser would affect growth and pathogenic properties of Candida albicans.MethodsA concentration of 106 viable cells/ml of Candida albicans were used in the preparation process. Four groups were created from the specimens. Culturing of the control group was completed with no intervention. The other 3 groups received laser radiation for 60 seconds at a power of 1W. The 2nd and 3rd groups were irradiated with diode laser at a wavelength of 940 nm and 980 nm respectively. The 4th group was irradiated with Nd-YAG laser at a wavelength of 1064 nm. Turbidimetric growth was defined as variations in the optical density of fungal growth. These measures were made at three different times: baseline, 48 hours, and 72 hours.ResultsIn both groups of diode laser, the growth of Candida albicans showed no remarkable differences at baseline, after 48 and 72 hours using a power of 1 W and duration of 60 seconds. The Nd-YAG group showed significant increase in optical density after 48 hrs then significant decrease after 72 hrs. The optical density values in the control group showed no notable difference between the control and diode study groups at different time periods. However, the Nd:YAG group showed a statistically significant difference compared to the control and the 2 diode laser groups.ConclusionsDifferent laser parameters have a different effect on growth and pathogenic properties of Candida albicans. Diode laser therapy with wavelengths 940 and 980 nm used in continuous mode with power of 1 W for duration of 60 seconds can result in proliferation of Candida albicans instead of destroying them. Nd:YAG laser, used in pulsed mode, with power of 1 W for a duration of 60 seconds can be used to destroy Candida albicans and therefore, can be used as an effective treatment for denture stomatitis.

Evaluation of the results of complex medical rehabilitation of patients with polyposis rhinosinusitis in the long-term period

BACKGROUND: Previous studies on the comparative evaluation of the effectiveness of the course application of therapeutic physical factors during the complex medical rehabilitation of patients with polypous rhinosinusitis showed a rather high efficiency of the additional use of complex physiotherapy (alternating magnetic field and low-intensity laser therapy) in enhancing the regression of the main clinical manifestations of polypous rhinosinusitis and improving the quality of life (QoL) of patients. Considering the chronic and often recurrent nature of polypous rhinosinusitis, along with the relief of the main clinical manifestations of the disease and improvement in the quality of life of patients after treatment, medical rehabilitation of patients should also cover the long-term period.
 AIM: Evaluation of the results of complex medical rehabilitation of patients with polyposis rhinosinusitis in the long-term period (after 6, 12 and 18 months) and determination of the optimal time parameters for a repeated course of physiotherapy aimed at maintaining the achieved clinical effect and the level of quality of life of patients.
 MATERIALS AND METHODS: The study was performed with the participation of 120 patients with moderate to severe polypous rhinosinusitis and uncontrolled course. All patients were divided into 4 groups by simple fixed randomization. The first group (control, 30 patients) received only basic therapy, including endonasal application of Nasonex 2 doses 2 times a day and daily twice daily lavage of the nasal mucosa. Patients of the second group (comparison group 1, 30 patients) were additionally injected subcutaneously with dupilumab at a dose of 300 μg once every two weeks. In the third group (comparison group 2, 30 patients), against the background of the administration of dupilumab, exposure to an alternating magnetic field was performed. using the apparatus MAGNIT Med TeCo. Patients of the fourth group (main group, 30 patients), in addition to the volume of treatment of patients of the third group, received low-intensity laser radiation of the red spectrum (633 nm) using the AZOR-2K-02 apparatus.
 RESULTS: Positive dynamics in terms of assessed clinical indicators throughout the entire observation period was noted only in the comparison groups and the main group. The maximum severity of positive changes was determined in the main group after 6 and 12 months of rehabilitation, exceeding the achieved values in the group with dupilumab. The follow-up period made it possible to establish that 18 months after the start of rehabilitation, there were no significant differences between these groups. The dynamics of the parameters of the microcirculatory tissue system in the comparison groups and the main group in the long-term period indicated the formation of compensatory-adaptive processes aimed at eliminating congestion in the nasal mucosa and associated hypoxia, as well as the normalization of oxygen metabolism and trophism of tissues prone to chronic inflammation.
 CONCLUSION: The results obtained convincingly prove the effectiveness of additional course use of an alternating magnetic field in combination with low-intensity laser therapy. The use of this technology, implemented against the background of ongoing biological therapy, shows its increased efficiency up to 12 months after the start of medical rehabilitation. It is advisable to conduct a second course of physiotherapy based on the complex use of an alternating magnetic field and low-intensity laser radiation 9–12 months after the start of medical rehabilitation.

Modification of AgNP-Decorated PET: A Promising Strategy for Preparation of AgNP-Filled Nuclear Pores in Polymer Membranes.

Polymer-based membranes represent an irreplaceable group of materials that can be applied in a wide range of key industrial areas, from packaging to high-end technologies. Increased selectivity to transport properties or the possibility of controlling membrane permeability by external stimuli represents a key issue in current material research. In this work, we present an unconventional approach with the introduction of silver nanoparticles (AgNPs) into membrane pores, by immobilising them onto the surface of polyethyleneterephthalate (PET) foil with subsequent physical modification by means of laser and plasma radiation prior to membrane preparation. Our results showed that the surface characteristics of AgNP-decorated PET (surface morphology, AgNP content, and depth profile) affected the distribution and concentration of AgNPs in subsequent ion-track membranes. We believe that the presented approach affecting the redistribution of AgNPs in the polymer volume may open up new possibilities for the preparation of metal nanoparticle-filled polymeric membranes. The presence of AgNPs on the pore walls can facilitate the grafting of stimuli-responsive molecules onto these active sites and may contribute to the development of intelligent membranes with controllable transport properties.

Investigation of laser-induced contamination on dielectric thin films in MHz sub-ps regime

High-repetition rate diode-pumped sub-ps lasers are widely used in the industrial sector for high-quality material processing applications. However, for their reliable operation, it is crucial to study the power handling capabilities of the optical components used in these systems. The optical components, such as mirrors, gratings, dichroic filters, and gain media, are designed based on dielectric thin films. When subjected to high-intensity laser radiation, the phenomenon of laser-induced contamination (LIC) can lead to the growth of a nanometric, highly absorbent layer on an irradiated optical surface, which can result in transmission or reflection loss and eventual permanent damage. In this study, we investigate LIC growth on dielectric oxide thin films in an air environment irradiated by MHz sub-ps laser at 515 nm. We examine the effect of thin film deposition method, material, and thickness on LIC growth dynamics. The irradiated spots on the surface are inspected using multiple observation methods, including white light interference microscopy and fluorescence imaging. Our results show that the LIC growth dynamics depend on the laser intensity and irradiation time and can be affected by the thin film deposition method, material, and thickness. These findings could be used to inform the development of more resistant optical components, ensuring long-term reliable laser operation required for industrial applications. The study highlights the need for validating optical components using tests that closely mimic real-world applications and provides insight into the complex processes that lead to LIC.

Welding between confinements as a new approach for high deposition rate additive manufacturing with laser-assisted double wire welding with nontransferred arc

Laser-assisted double wire welding with nontransferred arc uses an electric arc to melt two welding wires fed toward each other. The molten material drips onto the substrate, where it is joined to the substrate without undercuts by means of oscillated laser radiation. The process offers possibility of creating structures with high deposition rates (8.4 kg/h), but faces challenges in fulfilling the requirements for surface properties and geometric accuracy. One approach to meet the requirements is to confine the final seam geometry by applying the melt into a mold. Such a confinement can be a wall previously applied by a process with higher geometric accuracy. An investigation of this approach was carried out by studying the deposition of mild steel weld beads within two confining structures, in this case, a groove. A particular interest in the evaluation is connection of the weld bead to the base material in the corners, the bottom surface, and the side surface of the groove. In the first step, weld beads are deposited in 12 mm wide grooves in a mild steel substrate with variable laser beam oscillation amplitudes of 10–13 mm. In the second step, several layers are deposited with variable welding speeds. The oscillation amplitude that generates the best connection in the corners is 13 mm. Bonding on the bottom and side surfaces could be achieved with all parameter sets. When applying several layers, the best lateral connection in the groove was produced with a welding speed of 200 mm/min.

Structure, optical properties, TD-DFT simulations for nanosecond and continuous laser irradiation of vanadium antimony borate glass doped with nickel ferrite

Borate antimony glass doped with vanadium oxide V2O5 encoded into a [BSV glass system] was prepared with the traditional melt quenching technique. The Nickel ferrite [NiFe2O4] was prepared using Flash auto-combustion and mixed at a fixed ratio of 0.05 gm into the glass matrix to form a BSV- composite glass system [BSV / NiFe2O4], which was also prepared using the traditional melt quenching technique. The X-Ray diffraction pattern was used to characterize the glass samples and indicated their amorphous structure, with different structure phases for different levels of V2O5 content. Ranging from 200 to 1100 nm, UV–Vis spectroscopy was used to study the optical properties of the samples. The glass was found to absorb electromagnetic waves with wavelengths lower than 500 nm, while the energy gap decreased from 2.46 eV for 0.1 mol% V2O5 to 2.39 eV for 0.5 wt% V2O5. The Urbach energy also had the same behavior, and decreasing from 0.226 to 0.217 eV. On the other hand, the refractive index increased when V2O5 was added. The thermal characteristics of a [BSV / NiFe2O4] system, such as, glass transition temperature {T}_{G}, onset temperature {T}_{X}, crystallization temperature {T}_{C} and melting temperature {T}_{m}, were studied using a Differential Scanning Calorimeter. Using continuous and pulsed laser radiation, a [BSV-0.1 V2O5 / NiFe2O4] sample was exposed to laser irradiation to observe its effect on the optical features of the glass. Laser irradiation significantly changed the absorbance spectrum, while the energy gap decreased as time increased. The pulsed laser was found to have a more power-full and uniform effect compared to continuous laser. Time-dependent density function theory was used to optimize the geometrical structure of the glass and study the effect of the formation of 4- coordinate boron atoms on its properties.

Detection of extreme temperatures via emission from MOFs of a varied structure

Detection of extreme temperatures plays a key role in metallurgy, aerospace, nuclear industries, and even astronomy. Herein, materials and optical technologies capable of detecting the temperatures above 3000 K are still in their infancy. Here, we report on a detection of 3800 to 4500 K through the emission of a blackbody, for which the metal-organic frameworks (MOFs) are used. The rapid heating of MOFs by laser radiation leads to the threshold blackbody emission (centered from 650 to 750 nm), the corresponding temperature of which is directly related to the structure of MOF. The results on such structure-related temperatures of the blackbody emission of MOFs, thereby, expand their use in photonics and sensing in general.

Thermo-photobiomodulation of stem cells

The most important task of cell transplantology is to activate the proliferative potential of mesenchymal stem cells (MSCs) before receiving bone marrow cells from a donor. This is necessary to increase a sufficient number of MSCs in early passages, when the probability of chromosomal mutations is still low. The proliferative activity of cells can be activated using photobiomodulation (PBM) by exposure to lowintensity laser radiation in the visible and near-infrared ranges. Recently, it was shown in vitro that the combination of PBM and moderate laserinduced heating can lead to a significant increase in the efficiency of MSC colony formation. The main objectives of the study are to find the optimal parameters for such a combined effect and answer the question about the possibility of a synergistic effect of thermal heating and laser radiation. MSCs isolated from rat bone marrow were used for the experiments. MSCs were exposed to short-term laser radiation of moderate power with a wavelength of 980 nm and an energy density of 68-340 J/cm2, accompanied by moderate heating of the cell suspension. Vials with grown colonies were photographed, then their number, size and number of cells in individual colonies were determined using special digital image processing methods. It was found that under optimal parameters, exposure to laser radiation of moderate power leads to an increase in the number of colonies by 4.1±0.5 times, and the total number of cells by 3.3±0.4 times compared to the control. It has been shown that this increase in cell number occurs as a result of the synergistic effect of photobiomodulation and moderate heating. Activation of colony formation after laser stimulation of MSCs occurs due to the migration of cells from the initially formed colonies with the subsequent formation of additional colonies by separated cells.

Selective lethal impact of blue laser radiation compared to high-power LED irradiation on naturally grown biofouling in the context of underwater biofouling cleaning

Technological advances in blue laser sources are expanding the possibilities for using high-power laser radiation, particularly in the range of 1 kW and above, in marine environments, due to the reduced absorption of laser radiation below 550 nm in water. These developments are creating new opportunities for high power laser underwater applications. One key application is the removal of biofouling from submerged technical surfaces like ship hulls by causing lethal damage to attached organisms. This research investigated the effect of radiation power density on lethal damage to organisms, focusing on naturally grown biofouling. Experiments were carried out with different power densities in the range from high-power blue light emitting diodes (LED) at 0.02 W/mm² to high-power blue lasers at 3.88 W/mm². These results help to understand the relationship between radiation parameters and biological responses, which is crucial for optimizing environmentally friendly technologies.

Conditions for the efficiency of optical limiting based on experiment and quantum chemical calculations.

The development of suitable protection against laser radiation has proven challenging due to the lack of predictive models. The purpose of this article is to exclude the existing drawback by creating a universal strategy based on correlations between experimental and theoretical data characterizing the nonlinear optical properties of absorbers, for which a series of low-symmetry penta(chloro)cyclotriphosphazene-substituted monophthalocyanines was chosen. To search for correlations on a small series of dyes, we used the advanced algorithm CORRELATO, which has been proven to construct even the most unusual relationships demonstrated in our previous works. Due to the reducing symmetry of molecules, large values of the nonlinear absorption coefficient (more than 3000 cm GW-1) and, as a result, wide dynamic ranges (up to 630) with a high degree of attenuation of nanosecond laser radiation (10-20 times) were achieved. The use of the finite-field DFT method has allowed the calculation of dipole moments, polarizabilities and hyperpolarizabilities. The numerical data obtained during the calculations were used in correlations of theory vs. experiment to derive mathematical expressions (inequalities) to assess the effectiveness of absorbers in limiting the power of laser radiation.

АНАЛИЗ ПРИМЕНЕНИЯ ЛАЗЕРНОГО ИЗЛУЧЕНИЯ ДЛЯ КОНТРОЛЯ СОРНОЙ РАСТИТЕЛЬНОСТИ

The use of chemical agents to remove weeds contributes to the selection of their resistant forms and leads to an increase in the dosages of the means used. A method of removing weeds using laser radiation is proposed. (Research purpose) The research purpose is analyzing the application and justification of the operation modes of a diode laser for the weeds control. (Materials and methods) The experiment was carried out on the developed stand, which included an LT-4LDS-V1 diode laser mounted on a trolley, with the possibility of moving it along the X, Y and Z axes to accurately adjust the position relative to weeds. A three-factor experiment was performed to determine the optimal mode in which complete stem cutting is not required. The power of the laser emitter, the distance to the processing object and the diameter of the stem were used as factors affecting the processing time taken as a response function. Experiments were carried out on three types of weeds: field dandelion, creeping wheatgrass and squat mallow. Carried out using an RGB camera, digital tracking of the moment of fracture of the stems was carried out. We performed data processing, analysis and statistical processing using Mathcad, PlanExp software tools. (Results and discussion) Regression equations were obtained, the results of experiments were statistically processed, and the response function optima were found. The optimal parameters and operating modes of the diode laser were determined. It was found that at constant values of the power factor (20 watts), a distance of 50 millimeters to the object, the process of burning the dandelion stalk was 3.792 seconds (stalk thickness 3.5 millimeters); creeping wheatgrass 1.06 seconds (stalk thickness 0.5 millimeters); squat mallow 2.79 seconds (stalk thickness 3 millimeters). (Conclusions) It was found that 7 days after the experiment, the use of laser exposure led to the destruction of 81 percent of dandelions, 93 percent of wheatgrass and 75 percent of hollyhocks from their total number. Using the results obtained, the possibility of using laser radiation in the established operating modes to weed control in the field was confirmed.

Comparative evaluation of transscleral laser exposure in anatomical experiment

This study comparatively analyzed the morphology of eye tissues after laser exposure using the latest generation of transscleral laser techniques - micropulse transscleral cyclophotocoagulation (MP-TSCPC) and laser activation of scleral hydropermeability (LASH) - in an anatomical experiment. The study used pulsed-periodic radiation of an Er-glass fiber laser (λ=1.56 μm) and radiation of a diode laser (λ=0.81 μm) in the micropulse mode. A comparative morphological evaluation of histological preparations of target scleral and ciliary body (CB) tissues was performed with the study of laser-induced changes occurring after LASH and MP-TSCPC. The study of histological preparations obtained after MP-TSCPC and LASH did not reveal any noticeable signs of an inflammatory reaction or significant destructive changes. There were no signs of pronounced coagulative changes in the form of disorganization of connective and muscle tissue in the exposure area. At the same time, MP-TSCPC was accompanied by thinning and discontinuity of the CB pigment epithelium in the projection of its flat part and expansion of the gaps between the anterior connective tissue fibers fixing the CB to the sclera, which is likely a factor contributing to uveoscleral outflow. After LASH, in the irradiated areas at the level of the outer layers of the sclera (¾ of its thickness) located in the projection of the flat part of the ciliary body, multiple slit-like cavities and enlargements (stretching) of interfiber spaces were revealed with simultaneous compaction of the inner part of the sclera (¼ of its thickness). The identified morphological changes may indicate certain differences in the mechanisms of intraocular pressure (IOP) reduction after MP-TSCPC and LASH. The results of this study suggest that the enhancement of uveoscleral outflow of intraocular fluid and the hypotensive effect after MP-TSCPC may be associated with laser-induced expansion of the interspaces between the anterior connective tissue fibers of the CB in the suprachoroidal space. With LASH, the possible mechanism of lowering IOP may be related rather to an increase in transscleral filtration due to the appearance of slit-like interfiber spaces in the sclera, caused by local contraction of scleral fibers in the area of laser exposure. The absence of pronounced destructive changes at the histological level indicates the gentle nature of both laser techniques and the possibility of expanding the indications for the use of LASH in the treatment of glaucoma, including at its earlier stages.

Investigation of asymmetry reduction for surface structuring and destructuring by laser remelting

Lasers are widely used for structuring metallic surfaces by ablating material. An alternative approach for laser structuring is surface structuring by laser remelting (WaveShape), which is based onthe continuous remelting of a thin surface layer using laser radiation while simultaneously modulating the laser power. The structures are generated by redistribution of the molten material. The structure height and the structure wavelength of periodic structures created using WaveShape can be precisely adjusted by the adaption of various process parameters. However, the structures produced are mostly asymmetrical. An asymmetric structure refers to a structure that is not symmetrical and is inclined in or against the scanning direction. In the context of this work, the asymmetry of the structures was significantly reduced through two different process adaptations. As a first adaption, a compensation term is added to the laser power modulation, which is calculated from the difference profile between a target profile and a structured profile. With this adaption, the shape deviation of an asymmetrical structure could be decreased by 66 %. Asymmetry can be reduced efficiently, although the difference profile required must be determined from a preliminary process step. As a second adaption, a modulation of the scanning speed is investigated with which shape deviation can be decreased by 40 %. Asymmetry is not as effectively prevented as when using the first adaption, but the adaption can be performed without the difference profile. Another aim was to investigate the destructuring, i.e. the removal and therefore smoothing, of asymmetric structures. Using the inverse laser power modulation for destructuring, the structure height of a symmetrical structure can be reduced by 91 % while the structure height of an asymmetric structure can be reduced by 68 %. To increase the efficiency of destructuring of an asymmetrical structure, iterative destructuring was investigated. With two iterations of destructuring, the structure height was reduced by 90 %. As a second approach for more efficient destructuring of asymmetric structures an adaption of the laser power modulation via a compensation term was investigated. The structure height could be reduced by 86 %. In summary, results show that asymmetry can be prevented when structuring with WaveShape and that asymmetric structures can be destructured efficiently.