Energy Density Of Laser Radiation Research Articles

Transformational features of the vein wall during a long-term period of endovenous laser ablation using 1910 nm laser radiation. Results of in-vivo experiments.

In this paper, results of in-vivo experiments on the animals of endovenous laser ablation (EVLA) using laser radiation with the wavelength 1910 nm are reported. The results of histological studies of the vein segments removed immediately after the procedure and in a long-term period (30 days and 3 months) are presented. Their structural transformation and the obliteration degree of the vein lumen using different values of the linear energy density of laser radiation (LEED=7.5; 15; 20 J/cm) are estimated. Edilbay breed of sheep (males) were used as experimental animals. Laser radiation with a wavelength of λ=1910 nm and power of Р<inf>rad</inf> = 1.5, 3, 4 W was used for EVLA experiments, and speed of fiber traction (v) was 2 mm/s. 8 days after EVLA stitches and an elastic bandage were removed. Animals were observed for 3 months in the vivarium. Animals have duplex ultrasound scanning of coagulation veins under anesthesia, after analysis vein segments were excised for histological examination. As a result, the damage degree to the vein wall tissues (intima, media, adventitia) and peri-venous tissues was revealed. It is shown that in the long-time period, the intima and partial muscle layer transformed to connective tissue. EVLA using laser radiation with a higher value of LEED led to the growth of connective tissue, oedema of all vein layers and peri-venous tissue. The lumen closure occurred due to clot and the vein wall transformation, a maximum value was 25% using LEED=20 J/cm. The connective-tissue transformation of the coagulated vein occurs in a long-term period and more pronounced for higher LEED. However, features of vein hemodynamics of animals and differences between the clot formation process of human varicose veins and healthy animal veins lead to incomplete occlusion. These features should be taken into account during extrapolation results of experiments on animals in clinical practice.

Optimization of energy parameters for laser-induced PDT of cervical tissues using numerical simulation and fluorescent monitoring

The main problem in the photodynamic therapy (PDT) of tumors is insufficient light exposure to tissue or the appearance of undesirable surface effects. The reason is the irregular distribution of the absorbed light dose by depth. The influence of the spot diameter on the relative fluence rate in the near-surface layer of the cervical tissue was studied by Monte Carlo simulation. Photodynamic exposure with chlorine-type photosensitizer (PS) was carried out on the tissue model with laser 660 nm at the same power density with a change in spot diameter from 5 to 15 mm and radiation energy density from 100 to 300 J cm−2. The distributions of the fluorescence indices of the PS and the hemoglobin oxygenation degree by depth were obtained. The dependence of PS photobleaching on the energy density was established at the same power density and different spot diameters. The developed method increased the efficiency of PDT by delivering a sufficient energy density of laser radiation to the entire tumor tissue by depth without thermal damage, that allowed minimizing side effects and prevent possible growth and recurrence of the disease.

Peculiarities of pulsed laser deposition of thin InGaAsN films in an active background gas atmosphere

III-V-N compounds are a promising class of solid solutions that have the prospect of being used in optoelectronic devices operating in a wide spectral range up to 3 μm, as well as for increasing the efficiency of photodetectors, lasers in fiber-optic communication lines and telecommunication systems. In this work, the features of various methods for obtaining new III-V-N semiconductor materials are investigated. Thin InGaAsN films were obtained by pulsed laser deposition on GaAs (100) and Si (100) substrates in an active background gas atmosphere. Pulsed laser deposition of thin InGaAsN films was carried out using an In0.02Ga0.98As target in an atmosphere of a highly pure argon-nitrogen mixture at a pressure of 2, 5, and 10 Pa. The source of laser radiation was an AYG:Nd3+ laser with a wavelength of 532 nm (second harmonic), laser radiation energy density of 2.3 J/cm2, pulse repetition rate of 15 Hz, and pulse duration of 10 ns. The substrate temperature was 350 °C, the deposition time was 60 minutes. It is shown that the surface of thin films is textured with microdroplets. It has been established that microdroplets on the surface of a thin film are formed by metallic indium. It has been established that the distribution of indium microdroplets over the film surface is mainly ordered in the form of lines. This phenomenon can be explained by the presence of misfit dislocations. The average size of microdroplets on the surface of the InGaAsN film on GaAs (100) was about 30 nm, and their density did not exceed 0.076 μm–2. For comparison, in films obtained on Si substrates at a pressure of 2 Pa, the highest microdroplet density was 0.26 μm–2. The lowest density of microdroplets on the surface (0.17 μm–2) was noted in samples of a thin film of InGaAsN on Si (100) obtained at a pressure of 10 Pa. It is noted that the intensity of the local phonon vibrational mode LVM InN at a frequency of 430 cm–1 increases with increasing pressure of the argon-nitrogen mixture during pulsed laser deposition in the Raman scattering spectra of InGaAsN films on Si. In the Raman spectra of InGaAsN films on Si, second-order phonon modes LVM InN and LVM GaN were detected at frequencies of 450 cm–1 about 470 cm–1, respectively. This confirms the presence of nitrogen in a thin InGaAsN film obtained by pulsed laser deposition. It is shown that an increase in the pressure of the argon-nitrogen gas mixture during pulsed laser deposition contributes to an increase in the nitrogen concentration in thin InGaAsN films on Si. It has been established that the nitrogen concentration in InGaAsN films obtained at a pressure of 10 Pa on GaAs (100) and Si (100) substrates differs insignificantly and amounts to 1.9 % and 1.8 %, respectively. The presented results will make it possible to create highly efficient photoelectric converters and photodetectors for the near and mid-infrared range up to 3 μm based on the obtained InGaAsN thin films.

Предпороговые эффекты при воздействии ультрафиолетовых лазерных импульсов на медь и ее сплавы

The prethreshold processes on the surface of copper and its alloys are investigated. In the absence of obvious traces of melting, while preserving the metal in a condensed state, under a nanosecond ultraviolet laser radiation energy density of 0.1–1.0 J/cm2, manifestations of high-temperature plastic deformation were observed. These are sliding and cracking along grain boundaries, within which crystallographic slipping was observed. A microprotrusion was formed on the surface of the irradiated zone, which was outwardly similar the distribution of laser radiation in the spot. The height of the microprotrusion reached 1 µm, and sometimes even more. An increase in the number of impacting impulses led to the accumulation of damage. The data obtained are in many ways similar to the acoustoplastic, electroplastic, and magnetoplastic effects. By analogy, we consider it possible to call the discovered effect optoplastic.

Prethreshold effects, when copper and its alloys were impacted to ultraviolet laser pulses

The prethreshold processes on the surface of copper and its alloys are investigated. In the absence of obvious traces of melting, while preserving the metal in a condensed state, under a nanosecond ultraviolet laser radiation energy density of 0.1-1.0 J/sm2, manifestations of high-temperature plastic deformation were observed. These are sliding and cracking along grain boundaries, within which crystallographic slipping was observed. A microprotrusion was formed on the surface of the irradiated zone, which was outwardly similar the distribution of laser radiation in the spot. The height of the microprotrusion reached 1 μm, and sometimes even more. An increase in the number of impacting impulses led to the accumulation of damage. The data obtained are in many ways similar to the acoustoplastic, electroplastic, and magnetoplastic effects. By analogy, we consider it possible to call the discovered effect optoplastic. Keywords: plastic deformation, optoplastic effect, crystallographic slip, laser.

On the method of calculating the energy density of laser radiation in a metal surface modification

Today, modification of metal surfaces using laser radiation (laser ablation) is one of the most common processing methods in various scientific studies. At the same time, there is no unified approach to estimating the energy of laser radiation impact on the metal surface, which significantly complicates the comparison of the results of studies performed at different parameters of laser radiation. In the present work, a universal method of calculating the energy density of laser radiation impact on the surface is presented. The formation of relief with identical geometric characteristics at different parameters of laser radiation, but with the same energy density of radiation effect on the surface being modified, was experimentally confirmed.

Photodynamic therapy as a treatment option for skin cancer, developed on scars

It is given a literature reference on the etiology, frequency and mechanisms of development, features of the clinical presentation and treatment options for skin cancer that has developed on scars. It is presented a detailed clinical observation of a patient with squamous cell skin cancer in the area of the right elbow joint, which occurred 67 years after the kerosene lamp burns of the skin of the right upper limb and the right half of the chest. The patient was initially treated with electron radiotherapy in the total focal dose 60 Gy with a partial effect, but after 10 months a relapse was diagnosed, for which multi-course photodynamic therapy was performed with a Photolon photosensitizer at a dose of 1.1 mg/kg; the way of light delivery was polypositional interstitial and distant, the laser radiation power density was 0.30 W/cm2, the laser radiation energy density was 200 J/cm2. The result of treatment is complete regression of the tumor, the patient was under regular observation without any signs of local, regional and distant metastasis. After 3 years, by the absence of signs of local relapse, the disease progression was diagnosed: metastatic lesion of the axillary lymph nodes on the right and multiple metastases in the lung tissue of both lungs. Treatment was performed: axillary lymphadenectomy on the right, targeted therapy with IgGl monoclonal antibodies directed against the epidermal growth factor receptor; on this background stabilization of the process was noted.

Effect of postgrowth processing technology and laser radiation parameters at wavelengths of 2091 and 1064 nm on the laser-induced damage threshold in ZnGeP2 single crystal

We report a study of the effect of postgrowth treatment of ZnGeP2 single crystals (low-temperature annealing, irradiation with fast electrons, polishing of working surfaces) and the conditions of exposure to repetitively pulsed laser radiation [wavelength (2091 or 1064 nm), pulse repetition rate, beam diameter, exposure time, sample temperature] on the laser-induced damage threshold (LIDT) of the surfaces of these crystals. It is found that thermal annealing of ZnGeP2 single crystals and their irradiation with a flux of fast electrons, which increase the LIDT at a wavelength of λ = 1064 nm, do not lead to a change in this threshold at λ = 2091 nm. It is shown that ZnGeP2 elements with lower optical losses in the spectral range 0.7 – 2.5 μm have a higher LIDT at λ = 2091 nm both immediately after fabrication and after postgrowth processing. An increase in the threshold energy density of laser radiation by a factor of 1.5 – 3 at λ = 2091 nm is revealed with a decrease in the crystal temperature from zero to –60 °C. The fact of reversible photodarkening of the propagation channel of laser radiation in ZnGeP2 in the predamage region of parameters is established by the method of digital holography.

Wide range optical and electrical contrast modulation by laser-induced phase transitions in GeTe thin films

The paper presents the results of a computational thermo-kinetic model of laser heating of GeTe thin films and their subsequent thermoconductive and radiative cooling. A comparison of this model and experimental results of observing of reversible phase transitions in thin films under impact of nanosecond pulsed laser radiation with «top hat» beam intensity distribution was performed. It was shown that the subsurface crystallization of amorphous GeTe thin film obtained on SiO2 substrates is started at threshold laser radiation energy density E = 7.5 mJ/cm2. Then crystallization process propagates up to substrate primarily in the rhombohedral α-GeTe phase in the range of E = 18.6–32 mJ/cm2 with the subsequent transition to the cubic β-GeTe phase in the range of E = 32–47.6 mJ/cm2 reaching the necessary temperatures for corresponding transitions. The reverse crystalline-amorphous transition is started at the laser energy density 62 mJ/cm2, when the film temperature reaches the melting temperature and is observed up to energy density 93 mJ/cm2 without ablation damage. It was shown that the values of energy densities, required for α-/β-phase transitions and reamorphization for the films obtained on native oxidized p-Si (100) substrates in comparison with ones required for the same transitions in films on SiO2 substrates are more on about 20–30%, because of significant higher thermal conductivity of p-Si (100) substrate. The high optical contrast in the spectral range from 200 nm to 22000 nm and high difference in electrical conductivity from σam = 0.66 Ω−1 cm−1 to σcr = 26.8 Ω−1 cm−1 between amorphous and cubic crystalline states was demonstrated. The observed experimental results are in good agreement with computational thermo-kinetic model.

Multilevel reversible laser-induced phase transitions in GeTe thin films

This paper presents the results of a study on the structural properties and dynamics of conductivity of thin (d ∼ 100 nm) films of germanium telluride depending on the phase states reversibly switched by nanosecond pulsed laser radiation with a «top hat» beam profile. It was determined that the threshold of laser radiation energy density at which the phase transition in GeTe thin films from the amorphous to crystalline state is in the range of E = 7.5 ÷ 47.6 mJ/cm2, and the threshold for the reverse transition from the crystalline to amorphous state starts from 47.6 mJ/cm2 and is observed up to 90 mJ/cm2 with no visible damage caused by the ablation. The full time of conductivity change associated with the phase transition between the amorphous and crystalline phases is τCA = 20.2 ns, while for the reverse crystalline to amorphous transition, the conductivity full change time it makes τAC = 52 ns.

A phase Ib study of near infrared photoimmunotherapy (NIR-PIT) using ASP-1929 in combination with nivolumab and for patients with advanced gastric or esophageal cancer (GE-PIT study, EPOC1901).

TPS457 Background: Near Infrared Photoimmunotherapy (NIR-PIT) is a newly developed, molecular targeted cancer therapy based on conjugating a near infrared silica-phthalocyanine dye to a monoclonal antibody, which result in necrotic cell death of targeted cancer cell immediately after exposure to near infrared light. Phase IIa trial of NIR-PIT with RM-1929 (anti-EGFR antibody cetuximab conjugated to IRDye 700DX) showed a 43% objective response rate (ORR) for recurrent head and neck squamous cell carcinoma (Cognetti DM, et al.ASCO 2019 abstr 6014). Meanwhile, PD-1 blockade reverses adaptive immune resistance, resulting in activation of tumor infiltrating lymphocyte after NIR-PIT in syngeneic mouse models (Nagaya T, et al. Cancer immunology research. 2019). The objective of this study is to investigate the safety and efficacy of the NIR-PIT using ASP-1929 (analogous to RM-1929) in combination with nivolumab for advanced gastric or esophageal cancer. Methods: The study is an open-label, single-arm, single-center, Phase Ib clinical trial. Eligible patients are with unresectable esophagogastric squamous cell carcinoma or EGFR positive adenocarcinoma after standard chemotherapy. Dose escalation cohort is designed to determine the recommended dose of laser irradiation energy density in a “3+3” design (50, 75, and 100 J/cm2). Nivolumab of 240 mg on Day 1 and ASP-1929 of 640 mg/m2 on Day 8 is administered, and laser irradiation is performed under endoscopy using the laser PIT unit on Day 9. In expansion cohort, approximately 20 patients will be enrolled. The primary endpoint is proportion of incidence of dose-limiting toxicity, and the secondary endpoints are proportion of incidence of adverse events, ORR, local complete response rate, progression-free survival (PFS), local PFS, overall survival, and proportion of incidence of device malfunction. We also investigate several biomarkers using pre- and post-treatment biopsied samples. First patient will be enrolled in December 2019. Clinical trial information: JapicCTI-194969.

Mechanism of hot spots formation in pentaerythritol tetranitrate under pulsed laser irradiation

The spectral, kinetic, spatial, and amplitude characteristics of emissions of pressed samples of PETN (pentaerythritole tetranitrate) by the first harmonic of a neodymium laser (1064 nm, 12 ns) are studied. It is found that at the moment of irradiation of PETN by laser pulses, hot spots are formed on the surface of the samples. The energy density of laser radiation varies in the range of 0.5–3 J/cm2. The characteristics of hot spots are determined by absorbing inhomogeneities and parameters of laser radiation. Multi-pulse excitation leads to the annealing of absorbing irregularities and increased threshold of optical breakdown. The received results are interpreted on the basis of ideas of the low-threshold optical breakdown as evolving within local (defective) regions of the PETN in the electric field of the light wave.

Эмиссионные свойства сплава Pb-Ba, активированного лазерным облучением

A comparative analysis of the effect of temperature and laser activation on the values of the secondary electron emission coefficient (SEEC) and the work function eφ of the alloy Pd-Ba (Ba - 1.5 at.%) was carried out. It is shown that the optimum energy density of laser irradiation is ~ 2 J∙cm-2. The main reasons for the decrease in the emission efficiency of Pd-Ba for prolonged warming have been determined.

Wear resistance of laser-induced annealing of AISI 316 (EN 1.4401) stainless steel

This paper presents an analysis of the impact of the laser annealing process on the wear resistance and corrosion properties of one of the most commonly used AISI 316 (EN 1.4401) stainless steels. The samples were irradiated using a common available fiber laser (Yb:glass) system in an ambient environment. Considering that laser radiation changes the morphology and physicochemical structure of the surface layer, as well as the mechanical properties, extensive research has been conducted. Electrochemical tests, accelerated corrosion tests in neutral salt spray, x-ray photoelectron spectroscopy chemical analysis, microscopic examination, roughness, as well as friction and wear, were carried out. This study has shown that by properly controlling the energy density of laser radiation, the corrosion resistance of the material can be significantly improved. It has also shown that layers coated with laser-induced oxides are more resistant to wear than the reference samples.

Graphene oxide reduction by solid-state laser irradiation for bolometric applications

We present a method for reduced graphene oxide (GO) patterning on the surface of GO film by a 445 nm solid-state laser with the adjustable fluence from 0.2–20 kJ cm−2. We demonstrate that the optimal argon concentration in air to obtain good quality reduced GO films is 90%. Varying the laser irradiation energy density allows controlling the resistance and IG/ID and IG/I2D ratios of Raman peak intensities. As a result, we demonstrate the possibility of forming of conductive patterns with a sheet resistance of 189 Ohm/□ and ∼1 μm film thickness by a local reduction of the GO. The fabricated structures reveal excellent bolometric response with a high speed and sensitivity to the radiation in the visible wavelength region.

Stable Products of Laser-Induced Breakdown of Aqueous Colloidal Solutions of Nanoparticles

The formation of stable products of water decomposition under laser exposure of aqueous colloidal solutions of nanoparticles is experimentally studied. Laser exposure of colloidal solutions leads to formation of H2, O2, and H2O2. The dependence of the yield of these products depends on the energy density of laser radiation inside the liquid and concentration of nanoparticles. The ratio H2/O2 depends on laser fluence and is shifted towards H2. There are at least to sources of H2O2, namely, laser-induced breakdown plasma and ultrasound induced by laser pulses in the liquid. The formation of both H2 and O2 is tentatively assigned to direct dissociation of H2O molecules by electron impact from laser-induced plasma.

The influence of periodical, interference laser micromachining on nano-crystallization of amorphous magnetic ribbons

The main problem connected with crystallization of amorphous magnetic materials from the FeSiB(X) group is the increase of their fragility with the increasing content of crystalline phase. To overcome this defect the possibilities offered by the interference, pulse laser heating of FeSiB ribbons were utilized. A simple, interference prismatic system at the output of Nd:YAG laser (8-10 ns, 2 J, 1064 nm) was used. The investigations included the influence of laser radiation energy density, number of laser pulses and their periodical, spatial surface arrangement on the crystallization process. Full Text: PDF ReferencesY.R. Zhang and R.V. Ramanujan, "A study of the crystallization behavior of an amorphous Fe77.5Si13.5B9 alloy", Mater. Sci. Eng. A 416, 161 (2006). CrossRef T. Alam, T. Borkar, S. Joshi, S. Katakamb, X. Chenc and N.B. Dahotre, "Influence of niobium on laser de-vitrification of Fe-Si-B based amorphous magnetic alloys", J. Non-Cryst. Solids 428, 75 (2015). CrossRef K.G. Pradeep, G. Herzer, P. Choi and D. Raabe, "Atom probe tomography study of ultrahigh nanocrystallization rates in FeSiNbBCu soft magnetic amorphous alloys on rapid annealing", Acta Mater. 68, 295 (2014). CrossRef S. Katakam, J.Y. Hwang, H. Vora, S.P. Harimkar, R. Banerjee and N.B. Dahotre, "Laser-induced thermal and spatial nanocrystallization of amorphous Fe-Si-B alloy", Scr. Mater. 66, 538 (2012). CrossRef J. Kusiński, A. Sypień, G. Kusiński and C. Nilson, "Microstructure and nanochemistry of Ca-doped cobalt oxide single crystals", Mat. Chem. Phys. 81, 390 (2003). CrossRef C. Smith, S. Katakam, S. Nag, X. Chen, R.V. Ramanujan, N.B. Dahotre and R. Banerjee, "Improved soft magnetic properties by laser de-vitrification of Fe-Si-B amorphous magnetic alloys", Mater. Lett. 122, 155 (2014). CrossRef Ch. Lu and R. H. Lipson, "Interference lithography: a powerful tool for fabricating periodic structures", Laser Photonics Rev. 4, 568 (2010). CrossRef K. Czyż, J. Marczak, R. Major, A. Mzyk, A. Rycyk, A. Sarzyński and M. Strzelec, "Selected laser methods for surface structuring of biocompatible diamond-like carbon layers", Diam. Relat. Mater. 67, 26 (2016). CrossRef A. Sarzyński, J. Marczak, M. Strzelec, A. Rycyk, K. Czyż and D. Chmielewska, "Laser micro-structuring of surfaces for applications in materials and biomedical science", Proc. SPIE, 10159, 101590A (2016). CrossRef

Laser Non-Contact Drug Delivery Methods: Mathematical and Experimental Substantiation.

This article outlines the existing methods for parenteral drug delivery. It also presents novel alternative methods based on laser technologies, namely laser impregnation and laser injection. A mathematical model is constructed to calculate laser impregnator's technical parameters, such as the energy density of laser radiation, pulse duration, and pulse repetition frequency. This model also makes it possible to estimate the increase in the diffusion rate of drug preparations when they are impregnated through multilayer structures, such as the skin. Moreover, this article presents experimental results on Er.YAG laser injection of various drug media, such as spirit solutions, aqueous solutions, and ointments. These preparations were injected into gelatinous gel and autopsy skin samples. Possible clinical application is considered for these laser transcutaneous drug delivery methods.

Laser induced modification of the properties of CuO single crystals coated by metal film

The properties of copper oxide CuO single crystals coated by Cu or Ag films before and after the surface treatment by YAG:Nd3+ laser radiation were studied. With an increase of energy density of laser radiation the drastic changes in the surface microstructure, elemental composition and electrical properties of the crystals under investigation were observed. The peculiarities inherent to the granular samples have not been revealed on the temperature dependence of the resistance. The modification of copper oxides properties by the influence of laser irradiation may be used to improve the characteristics of various devices based on them.

Characterization of low-temperature solution-processed indium–zinc oxide semiconductor thin films by KrF excimer laser annealing

We have employed KrF excimer laser annealing (ELA) treatment on sol–gel derived indium–zinc oxide (IZO) precursor films to develop a method of low thermal-budget processing. As-coated IZO sol–gel film was dried at 150°C and then annealed using KrF excimer laser irradiation under ambient air. The laser irradiation energy density was adjusted to 150, 250, 350, and 450mJ/cm2 to investigate the effects of laser irradiation energy density on the microstructure, surface morphology, optical transmittance, and electrical properties of laser annealed IZO thin films. Results of GIXRD and TEM-SAED indicated that the ELA IZO thin films had an amorphous phase structure. The surface characteristics and electrical properties of laser annealed IZO thin films were significantly affected by the laser irradiation energy density. It was found that the dried IZO sol–gel films irradiated with a laser energy density of 350mJ/cm2 exhibited the flattest surface, the highest average optical transmittance in the visible region, and the best electrical properties among all ELA samples.