Interaction Of Laser Light Research Articles

Enhanced laser conditioning using temporally shaped pulses.

Laser conditioning was investigated as a function of the temporal shape and duration of 351nm nanosecond pulses for fused-silica substrates polished via magnetorheological finishing. The aim is to advance our understanding of the dynamics involved to enable improved control of the interaction of laser light with the material to optimize laser conditioning. Gaussian pulses that are temporally truncated at the intensity peak are observed to enhance laser conditioning, in comparison to a Gaussian pulse shape.

Optics and spectroscopy of a single plasmonic nanostructure

We review the interaction of laser light with a single plasmonic nanostructure. Until recently, the extremely weak optical response of a single nanostructure had only allowed spectroscopic research on ensembles of nanoparticles, where both structural and material parameters vary from one nanoparticle to another and the optical response is therefore averaged over the ensemble. Measurements at the level of a single nanostructure provide an effective tool for investigating the fundamental optical and spectroscopic properties of nanostructures, allowing insight into the mechanisms of elementary physical processes and permitting one to avoid the averaging procedure with the inevitable loss of physical information. The diverse range of linear-interaction optical phenomena occurring in a weak light field is reviewed and nonlinear interaction with high-intensity radiation is discussed.

O uso terapêutico do LASER de Baixa Intensidade (LBI) em algumas patologias e sua relação com a atuação na Fonoaudiologia

O uso da luz LASER Terapêutico de Baixa Intensidade (LBI) ou Low Level Laser Therapy (LLLT), é multidisciplinar, sendo este utilizado por vários profissionais: médicos, dentistas, fisioterapeutas, enfermeiros, físicos, biólogos, engenheiros, etc. A Fonoaudiologia começa a despertar o interesse em integrar esse grupo de profissionais, sendo um recurso totalmente terapêutico, não invasivo, sem efeitos tóxicos e colaterais que agrega no trabalho terapêutico e estabelece um prognóstico excelente de reabilitação. Por esse motivo, objetivou-se coletar alguns artigos científicos que abordam os fundamentos físicos e bioquímicos da interação da luz do LASER com o tecido biológico vivo e sua aplicabilidade terapêutica nas especialidades da saúde onde encontramos também a atuação da Fonoaudiologia. Para isso foram selecionadas algumas patologias relacionando-as ao uso do LBI: disfunção temporomandibular (DTM), paralisia facial, disfagias por disfunção motora, cicatrização tecidual incluindo as fissuras mamilares, principal responsável pelo abandono do aleitamento materno. No escopo das patologias, será descrita a ação do LASER e seu efeito biomodulador nos processos: inflamatórios, álgicos, cicatriciais, edematosos, de reparação nervosa e muscular. Conclui-se que o LBI é um avanço tecnológico e uma importante ferramenta terapêutica em campos distintos, significando uma grande evolução em toda a área da saúde, inclusive na Fonoaudiologia. É fundamental destacar que os artigos apresentam falta de padronização na dosimetria e sugere-se que próximos estudos sejam elaborados com a padronização dos documentos da World Association for Laser Therapy (WALT).

Femtosecond laser irradiation of olivine single crystals: Experimental simulation of space weathering

Space weathering is one of the most common surface process occurring on atmosphere-free bodies such as asteroids and the Moon. It is caused mainly by solar wind irradiation and the impact of micrometeoroids. In order to simulate space weathering effects, in particular those produced by hypervelocity impacts, we produced microcraters via ultra-short (∼100 fs) laser irradiation of crystallographically oriented slices of forsterite-rich (Fo94.7) olivine. The main advantages of the application of a femtosecond laser radiation to reproduce the space weathering effects are (1) the high peak irradiance (1015 W cm−2), which generates the propagation of the shock wave at the nanosecond timescale (i.e., timescale of the micrometeoroid impacts); (2) the rapid transfer of energy to the target material, which avoids the interaction of laser light with the developing vapor plume; (3) a small laser beam, which allows the effects of a single impact to be simulated. The results of our spectroscopic and electron microscopic investigation validate this approach: the samples show strong darkening and reddening of the reflectance spectra and structural damages similar to the natural microcraters found on regolith grains of the Moon and asteroid 25143 Itokawa. Detailed investigations of several microcrater cross-sections by transmission electron microscopy allowed the detection of shock-induced defect microstructures. From the top to the bottom of the grain, the shock wave causes evaporation, melting, solid-state recrystallization, misorientation, fracturing, and the propagation of dislocations with Burgers vectors parallel to [001]. The formation of a short-lived vapor plume causes the kinetic fractionation of the gas and the preferential loss of lighter elements, mostly magnesium and oxygen. The high temperatures within the melt layer and the kinetic loss of oxygen promote the thermal reduction of iron and nickel, which leads to the formation of metallic nanoparticles (npFe0). The final stage of the microcrater formation is the cooling of the melt layer that results in its partial crystallization and the formation of olivine crystals with a palisade-like texture.

High-order multiphoton Thomson scattering

Electron–photon scattering, or Thomson scattering, is one of the most fundamental mechanisms in electrodynamics, underlying laboratory and astrophysical sources of high-energy X-rays. After a century of studies, it is only recently that sufficiently high electromagnetic field strengths have been available to experimentally study the nonlinear regime of Thomson scattering in the laboratory. Making use of a high-power laser and a laser-driven electron accelerator, we made the first measurements of high-order multiphoton scattering, in which more than 500 near-infrared laser photons were scattered by a single electron into a single X-ray photon. Both the electron motion and the scattered photons were found to depend nonlinearly on field strength. The observed angular distribution of scattered X-rays permits independent measurement of absolute intensity, in situ, during interactions of ultra-intense laser light with free electrons. Furthermore, the experiment's potential to generate attosecond-duration hard X-ray pulses can enable the study of ultrafast nuclear dynamics. More than 500 near-infrared laser photons are scattered by a single electron into a single X-ray photon. This is the first experimental evidence of high-order multiphoton Thomson scattering and validates the decades-old theoretical predictions.

YTTERBIUM PORPHYRINS COMPLEXES AND THEIR APPLICATION IN MEDICINE

Malignant tumors are the second most frequent cause of death after cardiovascular diseases. The photodynamic therapy based on the interaction of laser light with different photosensitizers was discovered in the 20th century as one of treatment methods. When using photosensitizers, the process of singlet oxygen and other active forms generation is observed in both malignant and healthy body tissues, which leads to a number of adverse reactions. More promising diagnostic compounds that do not have these disadvantages are ytterbium porphyrin complexes. These compounds slightly generate singlet oxygen under light irradiation, while maintaining a high level of tumorotropic agents as for therapeutic photosensitizers. This work continues a series of studies devoted to the analysis of physicochemical properties of Yb-complex 2,4-dimetoxyhematoporphyrin IX as a promising marker for fluorescent diagnostics of various tumors. Pharmaceutical compositions based on Yb3+-dimetoxyhematoporphyrin IX dipotassium salt were created. These compositions are capable of accumulating in the sites of inflammation and proliferation in diseases of mucosal membranes and cancer lesions. Toxicological and pharmacokinetic studies were carried out with the use of laboratory animals and volunteers. The analysis results showed that the pharmaceutical compositions are perspective for use in clinical practice.

Nanolocalized UV source of laser radiation

We show the results of optical nonlinear interaction of laser light with plasmonic nanostructures. Creation of a nanolocalized source of UV radiation (λ = 260 nm) of the record high intensity was demonstated. Possibility of use of the source for biomedical applications was shown.

Current Methods to Assess Human Cutaneous Blood Flow: An Updated Focus on Laser-Based-Techniques.

Several noninvasive techniques have been developed using laser light interaction in the skin to explore the skin's microcirculation. Combined with laser Doppler or LSCI, reactivity tests are used to explore skin endothelial and neurovascular function in humans, including PORH, LTH, PIV, and iontophoresis of vasodilators. Recent advances in our comprehension of the physiological pathways underlying these reactivity tests have been possible through topical or intradermal delivery of drugs that produce elevated local concentrations. Skin microvascular function has also been proposed as a prognostic biomarker or for evaluating the effect of drugs. Comprehension of the physiological pathways, together with recent technological improvements in microcirculation imaging, has provided reliable and reproducible tools to study skin microcirculation.

Progress in selective laser sintering using metallic powders: a review

Laser sintering is a newly well established additive manufacturing technique, which has higher capabilities to produce complex shapes models/parts in a short time period. In this technique, a solid model is directly produced according to computer aided design model, by fusing two adjacent layers together, with the interaction of laser light. These parts are widely used in industries like aerospace and automobile and for medical applications as well. This paper reviews the selective laser sintering process and its research progress with the use of metallic powders. The main focus of whole available research progress is to produce complex shape solid model/parts using different metallic materials having the desired mechanical as well as dimensional properties.

Radiation emission from ultra-relativistic plasma electrons in short-intense laser light interactions

Intense femtosecond laser light incident on overcritical density plasmas has shown to emit a prolific number of high-order harmonics of the driver frequency, with spectra characterised by power-law decays. When the laser pulse is p-polarised, plasma effects do modify the harmonic spectrum, weakening the so-called universal decay index p = 8/3 to 5/3. In this work appeal is made to a single particle radiation model in support of the predictions from particle-in-cell (PIC) simulations. Using these, we further show that the emission radiated by electrons -those that are relativistically accelerated inside the plasma, after being expelled into vacuum, the so-called Brunel electrons- is characterised not only by the plasma line but also by ultraviolet harmonic orders characterised by the 5/3 decay index.

In Vitro Mean Red Blood Cell Volume Change Induced by Diode Pump Solid State Low-Level Laser of 405 nm.

Objective: This study was conducted to investigate the effects of low-level laser (LLL) doses on human red blood cell volume. The effects of exposure to a diode pump solid state (DPSS) (λ = 405 nm) laser were observed. Background data: The response of human blood to LLL irradiation gives important information about the mechanism of interaction of laser light with living organisms. Materials and methods Blood samples were collected into ethylenediaminetetraacetic acid (EDTA)-containing tubes, and each sample was divided into two equal aliquots, one to serve as control and the other for irradiation. The aliquot was subjected to laser irradiation for 20, 30, 40, or 50 min at a fixed power density of 0.03 W/cm2. Mean cell volume (MCV) and red blood cell (RBC) counts were measured immediately after irradiation using a computerized hemtoanalyzer. Results: Significant decrease in RBC volume (p < 0.05, p < 0.0001, p < 0.0001, and p < 0.05, respectively) was induced with variation in laser doses.The highest response was observed with an exposure time of 40 min. This result was reproduced in RBCs suspended in a buffered NaCl solution. In contrast to this finding, laser-induced RBC volume change was completely abolished by suspending RBCs in a solution containing a higher concentration of EDTA. Conclusions: It was suggested that LLL can reduce RBC volume possibly because of the increased free intracellular Ca+2 concentrations, which activate Ca+2-dependent K+ channels with consequent K+ ion efflux and cell shrinkage.

Probing wave function collapse models with a classically driven mechanical oscillator

We show that the interaction of a pulsed laser light with a mechanical oscillator through the radiation pressure results in an opto-mechanical entangled state in which the photon number is correlated with the oscillator position. Interestingly, the mechanical oscillator can be delocalized over a large range of positions when driven by an intense laser light. This provides a simple yet sensitive method to probe hypothetical post-quantum theories including an explicit wave function collapse model, like the Diosi & Penrose model. We propose an entanglement witness to reveal the quantum nature of this opto-mechanical state as well as an optical technique to record the decoherence of the mechanical oscillator. We also report on a detailed feasibility study giving the experimental challenges that need to be overcome in order to confirm or rule out predictions from explicit wave function collapse models.

Optical and electron microscopy study of laser-based intracellular molecule delivery using peptide-conjugated photodispersible gold nanoparticle agglomerates.

BackgroundCell-penetrating peptides (CPPs) can act as carriers for therapeutic molecules such as drugs and genetic constructs for medical applications. The triggered release of the molecule into the cytoplasm can be crucial to its effective delivery. Hence, we implemented and characterized laser interaction with defined gold nanoparticle agglomerates conjugated to CPPs which enables efficient endosomal rupture and intracellular release of molecules transported.ResultsGold nanoparticles generated by pulsed laser ablation in liquid were conjugated with CPPs forming agglomerates and the intracellular release of molecules was triggered via pulsed laser irradiation (lambda = 532 nm, tau _{pulse} = 1 ns). The CPPs enhance the uptake of the agglomerates along with the cargo which can be co-incubated with the agglomerates. The interaction of incident laser light with gold nanoparticle agglomerates leads to heat deposition and field enhancement in the vicinity of the particles. This highly precise effect deagglomerates the nanoparticles and disrupts the enclosing endosomal membrane. Transmission electron microscopy images confirmed this rupture for radiant exposures of 25 mJ/cm^{2} and above. Successful intracellular release was shown using the fluorescent dye calcein. For a radiant exposure of 35 mJ/cm^{2} we found calcein delivery in 81 % of the treated cells while maintaining a high percentage of cell viability. Furthermore, cell proliferation and metabolic activity were not reduced 72 h after the treatment.ConclusionCPPs trigger the uptake of the gold nanoparticle agglomerates via endocytosis and co-resident molecules in the endosomes are released by applying laser irradiation, preventing their intraendosomal degradation. Due to the highly localized effect, the cell membrane integrity is not affected. Therefore, this technique can be an efficient tool for spatially and temporally confined intracellular release. The utilization of specifically designed photodispersible gold nanoparticle agglomerates (65 nm) can open novel avenues in imaging and molecule delivery. Due to the induced deagglomeration the primary, small particles (~5 nm) are more likely to be removed from the body.Electronic supplementary materialThe online version of this article (doi:10.1186/s12951-015-0155-8) contains supplementary material, which is available to authorized users.

Effect of size and geometry of gold nanostructures in performance of laser-based hyperthermia: a multiscale- multiphysics modelling

The importance of hyperthermia as a promising method in disruption and removal of cancerous cells is well understood. One of the effective options of concentration of heat within a specific tissue is using laser and exploiting absorption properties of metallic nanostructures. In this report, the geometrical effect of gold nanostructures in the performance of laser based hyperthermia has been analyzed. The analysis is based on the consideration of absorption properties of gold nanostructures, interaction of laser light with a specific tissue containing nanostructures and the effect of generated heat on elevation of temperature inside the tissue. The analysis is performed using Mie theory (for extraction of absorption/scattering properties of nanostructures), Monte Carlo (MC) (interaction of light inside the tissue) and solving the heat equation (considering the elevation of temperature inside the tissue). We have compared the effect of a laser beam on the maximum temperature inside the tissue and the results indicate that focusing the beam size of the laser to half width will culminate in a 50% elevation of maximum temperature in the tissue, while the average temperature raise inside the tissue will not be altered.

Analysis of opto-thermal interaction of porcine stomach tissue with 808-nm laser for endoscopic submucosal dissection

In endoscopic submucosal dissection (ESD), the narrow gastrointestinal space can cause difficulty in surgical interventions. Tissue ablation apparatuses with high-power CO 2 lasers or Nd :YAG lasers have been developed to facilitate endoscopic surgical procedures. We studied the interaction of 808-nm laser light with a porcine stomach tissue, with the aim of developing a therapeutic medical device that can remove lesions at the gastrointestinal wall by irradiating a near-infrared laser light incorporated in an endoscopic system. The perforation depths at the porcine fillet and the stomach tissues linearly increased in the range of 2–8 mm in proportion to the laser energy density of 63.7–382 kJ/cm2. Despite the distinct structural and compositional difference, the variation of the perforation depth between the stomach and the fillet was not found at 808-nm wavelength in our measurement. We further studied the laser–tissue interaction by changing the concentration of the methyl blue solution used conventionally as a submucosal fluidic cushion (SFC) in ESD procedures. The temperature of the mucosal layer increased more rapidly at higher concentration of the methyl blue solution, because of enhanced light absorption at the SFC layer. The insertion of the SFC would protect the muscle layer from thermal damage. We confirmed that more effective laser treatment should be enabled by tuning the opto-thermal properties of the SFC. This study can contribute to the optimization of the driving parameters for laser incision techniques as an alternative to conventional surgical interventions.

МОДЕЛИРОВАНИЕ ВЗАИМОДЕЙСТВИЯ ЭЛЕКТРОМАГНИТНЫХ ВОЛН С ДИСПЕРСНЫМИ ЧАСТИЦАМИ НА ПОВЕРХНОСТИ ЖИДКОЙ СРЕДЫ

Numerical simulation of the interaction of laser light with dispersed particles at different temper-atures of the surface layer of the oceans and seas. We were obtained shape and amplitude of the acoustic signal formed during this interaction and assess the pressure amplitudes of the acoustic signals at different temperatures of the surface layer of the liquid. The evaluation of the ampli-tude of the acoustic pressure has built its dependence on the surface temperature of the liquid.

Progress of laser cooling of 12C3+ ions at the CSRe

SynopsisWe have performed a test run for laser cooling experiments with 12C3+ ion beams at an energy of 122 MeV/u at the CSRe with a pulsed laser. During this beamtime a lot of progress have been made. This was the first time we could successfully separate the 12C3+ ions and 16O4+ ions in the Schottky spectrum with the help of electron cooling. And our newly installed CPM detector worked well during the experiment. We tried to see effects from the interaction of the pulsed laser light with the stored 12C3+ ion beams, but no cooling effects could yet be observed.

Expanding applications, accuracy, and interpretation of laser speckle contrast imaging of cerebral blood flow.

Laser speckle contrast imaging (LSCI) provides a rapid characterization of cortical flow dynamics for functional monitoring of the microcirculation. The technique stems from interactions of laser light with moving particles. These interactions encode the encountered Doppler phenomena within a random interference pattern imaged in widefield, known as laser speckle. Studies of neurovascular function and coupling with LSCI have benefited from the real-time characterization of functional dynamics in the laboratory setting through quantification of perfusion dynamics. While the technique has largely been relegated to acute small animal imaging, its scalability is being assessed and characterized for both chronic and clinical neurovascular imaging.

Variants of the light pulses controlling under conditions of double radio-optical resonance

On the bases of semi-classical theory of the laser light interaction with a cold atomic cloud, specifically, of the electromagnetically induced transparency (EIT), repeated reproduction and modulation of the light pulses are investigated. A scheme of the light pulses control by the use of radio-frequency (RF) pulses is shown to be very effective. Short RF pulses of appropriate areas stimulate repeated playbacks of the output light pulses similar to the input one.

Measurement of Turbid Body Optical Properties Using Attenuation of Laser Light Intensity Techniques

The main objective of this work was to investigate the laser light interaction with highly diffusing tissue media like milk. In this work collimated transmission, fluence rate measurements and angular distribution of intensity measurements were made on three types of milks having different fat contents such as fresh cow milk (3.90%), skimmed milk (2.8%) and powdered milk and absorption coefficient.... , scattering coefficient.... , reduced scattering coefficient .... Œ , anisotropic factor g , scattering particle diameter d and particle size parameter X for different milks were observed. The results of the study revealed that fresh cow milk showed more fat content when compared to skimmed milk and powdered milk. Finally, the fluence rate measurement methods may be used to test the quality of milk more accurately.