Green Laser Light Research Articles

PHOTOINACTIVATION OF CANDIDA ALBICANS BIOFILM WITH GREEN LASER MEDIATED BY THE PAPAYA LEAF EXTRACT CHLOROPHYLL

This study aims to activate the effectiveness of Photodynamic Inactivation (PDI) as an antibacterial agent by using a green laser and papaya leaf chlorophyll extract to prevent Candida albicans cell death. Papaya leaf extract chlorophyll is known to have potential as a photosensitizer (PS) through its antimicrobial properties and ability to absorb optimal light photons at a wavelength range of 405–680 nm. Activation of chlorophyll molecules with appropriate light produces Reactive Oxygen Species (ROS), which are toxic to pathogenic microbes such as Candida albicans. The research method involves using PDI with a green laser light source and chlorophyll extract on Candida albicans biofilms. Four main treatment groups were applied, negative control (C-), positive controls with 10% (C1+) and 15% chlorophyll (C2+), irradiation for 60, 120, 180, 240, and 300 seconds (L1–L5), and combinations of irradiation with chlorophyll (L1F1–L5F2, where F1 for 10% chlorophyll and F2 for 15% chlorophyll), with measurements performed three times for each treatment. Living Candida albicans cells were detected using the XTT assay staining method. The results showed a significant decrease in activity in all treatment groups. Maximum activity was achieved in the L5F1 and L5F2 treatment groups with inactivation of 80% (p<0.05) and 83% (p<0.05), respectively. This study concludes that high papaya leaf extract chlorophyll concentrations combined with a green laser effectively inhibit Candida albicans biofilm.

Advanced CuO-Ag2WO4-Ni nanophotocatalyst in the synthesis of some chromeno[4,3-b]chromenes as effective lung cancer drugs

A novel heterogeneous nanocomposite CuO-Ag2WO4-Ni embedded within a foam matrix has been biosynthesized from Cressa Cretica leaves extract and comprehensively characterized using various techniques, including FT-IR, XRD, EDX, FE-SEM, DRS, TEM, and BET. This innovative nanocomposite demonstrates exceptional photocatalytic efficiency in the synthesis of some chromeno[4,3-b]chromenes, which have shown promise as effective medications in lung cancer treatment. The photocatalytic reactions are facilitated under a green laser light using ethanol as solvent. Compared to individual components of CuO-Ag2WO4-Ni, the nanocomposite exhibited superior performance in terms of light absorption, surface tunability, charge carrier generation, and stability. Noteworthy advantages of this nanocomposite include high reusability and ease of separation from the reaction mixture, thereby ensuring strong reproducibility. The foam structure plays a pivotal role in enhancing photocatalytic activity due to its high surface area and distinctive morphology. Mechanistic studies indicate that the generated holes and electrons effectively drive selective oxidation and reduction reactions, providing a reliable method for synthesizing a range of chromenes. The CuO-Ag2WO4-Ni exhibited remarkable stability across multiple catalytic cycles, with minimal morphological degradation and low leaching of the catalytic species, ensuring long-term effectiveness and cost efficiency for industrial applications. At the final part of this study, the MTT experiment was planned to investigate cytotoxicity of CuO-Ag2WO4-Ni on A549 lung cancer cells. This study affirmed that the performed nanomaterial has effective toxicity agaings the selected cell line.

Estimating differential penetration of green (532 nm) laser light over sea ice with NASA's Airborne Topographic Mapper: observations and models

Abstract. Differential penetration of green laser light into snow and ice has long been considered a possible cause of range and thus elevation bias in laser altimeters. Over snow, ice, and water, green photons can penetrate the surface and experience multiple scattering events in the subsurface volume before being scattered back to the surface and subsequently the instrument's detector, therefore biasing the range of the measurement. Newly formed sea ice adjacent to open-water leads provides an opportunity to identify differential penetration without the need for an absolute reference surface or dual-color lidar data. We use co-located, coincident high-resolution natural-color imagery and airborne lidar data to identify surface and ice types and evaluate elevation differences between those surfaces. The lidar data reveals that apparent elevations of thin ice and finger-rafted thin ice can be several tens of centimeters below the water surface of surrounding leads, but not over dry snow. These lower elevations coincide with broadening of the laser pulse, suggesting that subsurface volume scattering is causing the pulse broadening and elevation shift. To complement our analysis of pulse shapes and help interpret the physical mechanism behind the observed elevation biases, we match the waveform shapes with a model of scattering of light in snow and ice that predicts the shape of lidar waveforms reflecting from snow and ice surfaces based on the shape of the transmitted pulse, the surface roughness, and the optical scattering properties of the medium. We parameterize the scattering in our model based on the scattering length Lscat, the mean distance a photon travels between isotropic scattering events. The largest scattering lengths are found for thin ice that exhibits the largest negative elevation biases, where scattering lengths of several centimeters allow photons to build up considerable range biases over multiple scattering events, indicating that biased elevations exist in lower-level Airborne Topographic Mapper (ATM) data products. Preliminary analysis of ICESat-2 ATL10 data shows that a similar relationship between subsurface elevations (restored negative freeboard) and “pulse width” is present in ICESat-2 data over sea ice, suggesting that biased elevations caused by differential penetration likely also exist in lower-level ICESat-2 data products. The spatial correlation of observed differential penetration in ATM data with surface and ice type suggests that elevation biases could also have a seasonal component, increasing the challenge of applying a simple bias correction.

Fresnel–Arago laws: an easily feasible demonstration and laboratory exercise for students

The basic premise of this work was to create a simple experimental setup for the demonstration of Fresnel–Arago laws and the realization of an experimental exercise. An Iceland calcite is used as a beam splitter, and by adding a diverging lens (commonly used to magnify the image), a large image of overlapping spots is obtained at a short distance, visible to a wide audience. Additionally, by placing a diverging lens at different distances from the calcite, the level of the spots overlapping can be changed. The interference image is photographed by a smartphone and processed by one of the available applications for quantitative image processing. The experiment was carried out using red and green laser light. The same setup, with a diverging lens, also allows the reconstruction of the original Fresnel and Arago experiment with a thin metal cylinder. Quick and easy construction, relatively simple processing of the interference image, without the use of expensive devices (CCD camera, beam splitter, beam expander), and the good agreement between the nominal and measured laser light wavelengths, make this setup very suitable for realization as a student exercise for undergraduate and master’s students.

Fast and Mobile Cataract Detection by Applying Line Laser Eye Illumination

Cataract is observed when the eye lens becomes opaque. This condition causes blurred vision and is the main cause of blindness worldwide. Cataract diagnosis is usually performed during ophthalmologist examination using a slit lamp, which requires expertise, is expensive and bulky. In this study, we present a small handheld illumination setup for cataract detection. Ex-vivo porcine eyes are investigated to determine whether colored line lasers, 450 nm (blue), 520 nm (green) and 650 nm (red), which shine obliquely into the eye, are principally suited for detection of the Y shaped suture cataract and of cold cataract, respecting exposure limits of EU guideline 2006/25/EC. Camera images of the cataract exhibited good results under illumination with all line lasers. Observations with the physician’s eye led to an even better diagnosis of cataract. Generally, green laser light illumination was the best choice for cataract detection. With red laser light illumination it was also possible, but least suitable for this purpose. With this method, line lasers are a good choice for cataract identification, as cataract can be detected quickly and without much effort. This type of line laser illumination of the eye is safe and both types of cataract are detectable with all wavelengths. For the human eye, a further development of this system is conceivable.

Effect of Infrared and Green Photomodulation Exposure on the Number of Active Myosatellite Cells in Regenerating Muscles.

Reparative properties of infrared laser exposure are well known, but the effects of green laser light are little studied. We analyzed the effects of short (60 sec) and longer (180 sec) exposure to infrared (980 nm) and green (520 nm) laser on the number of activated myosatellite cells in the regenerating m. gastrocnemius of Wistar rats after infliction of an incision wound. Histological preparations were used for morphometric evaluation of myosatellite cells with MyoD+ nuclei. Increased numbers of MyoD+ nuclei were observed on days 3 and 7 after 60-sec exposure to infrared and green laser.

Photoregulation of the biosynthetic activity of the edible medicinal mushroom Lentinula edodes in vitro.

The findings of the study demonstrate the impact of low-intensity laser and quasi-monochromatic light on the biosynthetic activity of the edible medicinal fungus L. edodes during submerged cultivation. An artificial lighting installation based on matrices of light-emitting diodes (LED) emitting light at 470nm (blue), 530nm (green), 650nm (red), and argon gas laser (488nm) was used. Irradiation with blue and red LED and laser led to a shortening of the lag phase by 2days and an increase in the mycelial mass. Irradiation with laser light resulted in the highest mycelial mass yield (14.1g/L) on the 8th day of cultivation. Irradiation in all used wavelength ranges caused an increase in the synthesis of both extracellular and intracellular polysaccharides. Laser light at 488nm and LED at 470nm proved to be the most effective. Irradiation with red, green, and blue laser light caused an increase in the total amount of fatty acids in the mycelial mass compared to the control. A significant distinction in qualitative composition was observed: short-chain acids C6‒C12 compounds were produced under red light irradiation, whereas long-chain C20‒C24 were formed under green light irradiation. The most significant changes in the aromatic profile of the mycelial mass and culture liquid were recorded upon irradiation with green light. The content of aromatic components increased 24.6 times in the mycelial mass and 38.5 times in the culture liquid. The results suggest the possibility of using low-intensity quasi-monochromatic light for targeted regulation of L. edodes biosynthetic activity.

Low voltage visible light modulation for three colors (red, green, blue) by sputtered lithium niobate thin film

In this study, lithium niobate (LN) optical modulator devices were fabricated using cost-effective sputtered LN thin films. We successfully achieved a significantly small product of half-wave voltage and interaction electrode length (VπL) of 1.2, 1.0, and 0.75 V cm using red (λ = 638 nm), green (λ = 520 nm), and blue (λ = 473 nm) laser light, respectively. This small VπL is owing to the use of a low dielectric material of LaAlSiInOx for buffer insulator between LN waveguides and electrodes, and the change of geometrical configuration of the electrode. Thus, fabricating visible light modulators at low cost can be realized, and sputtered LN thin films can be adopted for visible light communications and consumer-based applications.

Influence of green laser light on the structural and optical properties of Mg-, Mn-, and Mn + Mg-doped copper oxide nanoparticles prepared by spin coating

Influence of green laser light on the structural and optical properties of Mg-, Mn-, and Mn + Mg-doped copper oxide nanoparticles prepared by spin coating

High-frequency resolution diamond nitrogen-vacancy center wide-spectrum imaging technology

High-resolution wide-spectrum measurement techniques have important applications in fields such as astronomy, wireless communication, and medical imaging. Nitrogen-vacancy (NV) center in diamond is well known for its high stability, high sensitivity, real-time monitoring, single-point detection, and suitability for long-term measurement, and has an outstanding choice for spectrum analyzers. Currently, spectrum analyzers based on NV centers as detectors can perform real-time spectrum analysis in the range of several tens of gigahertz, but their frequency resolution is limited to a MHz level. In this study, we construct a quantum diamond microwave spectrum imaging system by combining continuous wave-mixing techniques. According to the spin-related properties of the NV center in diamond, we implement optical pumping by 532 nm green laser light illuminating the diamond NV center. A spherical magnet is used to produce a magnetic field gradient along the direction of the diamond crystal. By adjusting the size and direction of the magnetic field gradient, spatial encoding of the resonance frequency of the NV center is achieved. The magnetic field gradient induces the Zeeman effect on the diamond surface at different positions, generating corresponding ODMR signals. Through accurate programming, we coordinate the frequency scanning step size of the microwave source with the camera exposure and image storage time, and synchronize them circularly according to the order of image acquisition. Ultimately, after algorithmic processing, we successfully obtain comprehensive spectrum data in a range from 900 MHz to 6.0 GHz. Within the measurable spectrum range, the system employs continuous wave-mixing, simultaneously applying resonant microwaves and slightly detuning auxiliary microwaves to effectively excite the NV center. This method triggers off microwave interference effects, disrupting the balance between laser-induced polarization and microwave-induced spontaneous relaxation. Specifically, microwave interference causes the phase and amplitude of the fluorescence signal to change, leading to the generation of alternating current fluorescence signals. This further enhances the response of the NV magnetometer to weak microwave signals. The method enables the system to achieve a frequency resolution of 1 Hz in the measurable spectrum range, and it can separately measure the frequency resolution of multiple frequency points with a frequency step size of 1 MHz. The research results indicate that the wide-spectrum measurement based on NV centers can achieve sub-hertz frequency resolution, providing robust technical support for future spectrum analysis and applications.

The effect of rose bengal activated with green diode laser light on selected Gram-positive and Gram-negative bacterial strains

In recent years the photodynamic activity of rose bengal activated with green light against selected bacterial strains has been reported. However, according to our knowledge, the differences between the sensitivity of Gram-positive and Gram-negative bacterial strains in the presence of this photosensitizer have not been described. The aim of the conducted research was to examine the antibacterial effect of 535 nm wavelength diode laser light in the presence of rose bengal as photosensitizer on selected reference bacterial strains: Pseudomonas aeruginosa, Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus. Sterile 96-well microtiter plates were used to determine the antibacterial activity of the green light and rose bengal solutions at various concentrations. The labelled bacterial suspensions were placed to each well of the 96-well microtiter plate filled with liquid medium LB and solution of rose bengal. The plates were exposed to green diode laser light. After 24 hours of incubation at 37oC, the turbidance was read in a spectrophotometer. The irradiation in the presence of photosensitizer can act in an antibacterial manner, either bacteriostatically or bactericidally. The tested strains exhibit different sensitivity to irradiation because of the structure of the cell wall, the presence of different bacterial pigments and photoreceptor proteins in some species of bacteria. Gram-positive bacteria, Staphylococcus aureus and Enterococcus faecalis were the most photosensitive strains due to the higher possibility of rose bengal penetration into the bacterial cell, leading to the bacteriostatic effect. Our results show that rose bengal may be applied in the treatment of Gram-positive infections.

The first experience of treating linear types of capillary angiodysplasia of the skin in children with green laser light λ 520 ± 10.0 nm

Introduction. The linear type of capillary angiodysplasia (LCA) is represented by pathologically dilated vessels of the capillary flow located between the epidermis and hypodermis. LCA may be both congenital and acquired. By the type of blood supply, LCA are arterial, venous and mixed. Local infections and injuries, excessive solar insolation and hormonal imbalance are noted among LCA causes. LCAs are benign lesions, but they may have complications which may be triggered, for example, by traumatic damage to a pathologically enlarged vessel. There is a large number of non-invasive and invasive curative methods of LCA removal: cryotherapy, electrocoagulation, sclerotherapy, laser photodestruction and others. Among disadvantages, various authors mark: high risk of scarring, hyperpigmentation and high rate of disease relapse.Purpose. To improve results of treatment of children with LCA by using laser light.Material and methods. 32 children having LCA were treated with transcutaneous selective photodestruction ( green laser light, wavelength of 520 ± 10.0 nm generated by Russian-made laser device "Malachit") in Clinical and Research Institute of Emergency Pediatric Surgery and Trauma in 2021–2022.Results. After treatment, 31 child had good results without residual vascular elements and scar deformation in the photodestruction zone. One patient required a repeated laser session because of remained residual elements after which she also had good results.Conclusion. The presented clinical trial has demonstrated that transcutaneous selective laser photodestruction with consideration of spatial localization of LCA structural elements in the skin, provides a precise treatment of pathological dilated vascular structures, practically without skin damage, and allows to achieve radical good clinical and aesthetic outcomes.

Investigating the Influence of Probe Pressure on Human Skin Using Diffusive Reflection Spectroscopy.

The skin has emerge as a compelling subject for investigation owing to its accessibility and the relatively straightforward application of optical procedures to it. Diffusive reflection spectroscopy (DRS) was employed to study the influence of probe pressure on human skin. A comprehensive non-invasive study was conducted, which covers almost all the important body parts for in vivo measurements. Reflection spectra were measured for the fingertip, forearm, forehead, neck, and foot under a set of probe pressures (0-265 kPa). Importantly, each tissue type's unique composition and morphology influenced the shape, size, intensity, and position of the recorded peak, highlighting the tissue-specific responses to pressure. In addition, time-based reflection spectroscopy was also performed on the forearm under blood occlusion for 5 min to study the effect. DRS measurements were performed on volunteers of different skin tones, including dark, medium, and fair. Later, a change in the intensity of the oxyhemoglobin peak was confirmed using a green laser light of a wavelength of 532 nm. Besides the dermal studies, diffusive reflection spectroscopy was also employed to investigate the probe pressure effect on human nails. A probe pressure ranging from 0 to 385 kPa was applied for nail spectroscopy. The same trend of intensity change was observed following the previous measurements. The suggested sensing system may be crucial in applications requiring pressure sensing when the human body is subjected to varying pressures, such as exercise, weightlifting, and other sports.

WO3-ZnS Photocatalyzed Synthesis of Some Substituted Benzimidazoles as Effective Agents against Gastrointestinal Cancer

Benzimidazoles, a class of nitrogen-containing heteroaromatic compounds, play a crucial role in the development of various important drugs. These compounds exhibit diverse biological functionalities. In this study, a novel and environmentally friendly photocatalytic route is proposed for the production of benzimidazoles. This method involves the oxidation of alcohol to aldehyde using air as the oxidant under visible-light conditions. Subsequently, fast condensation with o-phenylenediamine takes place, leading to the formation of 2-substituted benzimidazoles. The key mediator in this process is a newly developed photocatalyst called WO3-ZnS, which is activated by a commercial green laser light with a wavelength of 535 nm. To characterize the nanocomposite, several techniques including FT-IR, XRD, EDS, and FE-SEM were employed. These analyses provided valuable insights into the structure and properties of the nanocomposite. Moreover, Tauc’s method was utilized to estimate the optical band gap of the photocatalyst. The proposed photocatalytic process involves a radical pathway including reactive species such as •O2 - and OH•, along with h+. Stability and reusability experiments confirmed the reproducibility of the nano-photocatalyst in the reaction medium. Furthermore, the primarily in-vitro cellular toxicity of WO3-ZnS nanoparticles was evaluated using the HCT-116 human cancer cell line through MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) assay. The results demonstrated a significant reduction in cell viability, indicating the cytotoxicity of the nanoparticles against these cancerous cells. This finding highlights the potential of the synthesized nanoparticles as effective agents for combating gastrointestinal cancer.

DNA-CTMA Matrix Influence on Rhodamine 610 Light Emission in Thin Films.

Due to the increased application of lasers in different fields (industry, medicine, etc.), there is a growing need for new laser sources with good beam quality and variable emission wavelength. At the same time, for environmental reasons, the obtaining of novel eco-friendly active optical materials, such as those based on the deoxyribonucleic acid (DNA) biopolymer, with optimal light emission properties, is of high interest. The results obtained in this study of the temporal dependence of the transmittance and of the light emission in thin films of DNA-CTMA-Rhodamine 610 (at different Rhodamine concentrations) (DNA-CTMA-Rh610), when they are illuminated with continuous wave laser light at 532 nm (frequently used in the optical pumping of dye lasers), are presented and discussed. The transmittance results obtained for thin film samples are compared to those obtained for the DNA-CTMA-Rh610 solutions in butanol, from which the films have been made, and also with those obtained for Rh610 solutions in butanol with the same concentrations. The investigation was performed in order to assess the influence of the DNA-CTMA and of the green laser light at 532 nm wavelength on relevant chromophore properties such as light transmission and fluorescence emission. The results obtained revealed that the DNA-CTMA matrix has an active influence on the Rhodamine 610 emission, in the whole range of concentrations of the investigated samples.

Microfluidic mixology with bacterial stir bars

When activated via green laser light, the flagellar motors of bacteria can quickly and evenly mix reagents in microfluidics.

Photochemically induced thalamus infarction impairs cognition in a mouse model

BackgroundSmall subcortical infarcts account for up to 25% of ischaemic strokes. Thalamus is one of the subcortical structures that commonly manifest with lacunar infarcts on MRI of the brain. Studies...

Thermographic 3D particle tracking velocimetry for turbulent gas flows

Turbulent flows are characterized by diverse and unsteady three-dimensional (3D) features that require 3D measurements to study. In case of non-isothermal flows, combined 3D measurements of temperature and velocity are necessary. In this paper, a thermographic 3D particle tracking velocimetry (thermographic 3D-PTV) concept is introduced for simultaneous 3D temperature and velocity measurements in turbulent gas flows. It is based on sub-micron thermographic phosphor particles seeded into the flow as flow tracers with low response times of a few microseconds. To obtain each tracer’s position and velocity, the measurement region is illuminated volumetrically using a double-pulse green laser and Mie-scattered light is imaged by four double-frame cameras. Following the pinhole model-based calibration of all cameras, 3D particle positions are computed for both laser pulse-times using a fast minimum line of sight reconstruction code. Three-component velocities are derived from tracking individual particles between these time steps. For simultaneous 3D thermometry, temperature dependent luminescence emissions from the same phosphor particles are exploited. These emissions are excited using a UV laser synchronized with the first green laser pulse and imaged using two cameras equipped with spectral filters for ratiometric phosphor thermometry. As a result, instantaneous 3D fields of discrete temperature and velocity measurements are obtained throughout the volume. The concept is demonstrated in a turbulent heated gas jet emerging from a circular nozzle at a particle image concentration of 0.005 particle per pixel, where the symmetry of the velocity and temperature distributions about the jet axis is successfully reconstructed.

Eff ect of Different Laser Irradiation Parameters on the Viability of Bacillus Species

The genus Bacillus is present everywhere in the environment, it has environmental, industrial, and medical signifi cance. This heterogeneous group of bacteria shares unique characteristics, one of these is the resistance to physical and chemical agents. Laser light is one of the most interesting physical agents with a wide range of applications in all scientifi c fi elds. It has the ability to alter bacterial growth by triggering inhibitory or stimulatory mechanisms. In this study, laser parameters were varied to evaluate the eff ect of each one on the viability of Bacillus species. CW or chopped (532 nm) laser light at diff erent irradiation periods were examined. Results showed that tested bacterial species’ response to green laser light varied. Bacterial viability was dropped with increasing chopping frequency and exposure time. In conclusion, high repetition rate and prolonged exposure time increase the lethal eff ects of this type of laser

Microbial stir bars: Light-activated rotation of tethered bacterial cells to enhance mixing in stagnant fluids.

Microfluidics devices are gaining significant interest in biomedical applications. However, in a micron-scale device, reaction speed is often limited by the slow rate of diffusion of the reagents. Several active and passive micro-mixers have been fabricated to enhance mixing in microfluidic devices. Here, we demonstrate external control of mixing by rotating a rod-shaped bacterial cell. This rotation is driven by ion transit across the bacterial flagellar stator complex. We first measured the flow fields generated by rotating a single bacterial cell rotationally locked to rotate either clockwise (CW) or counterclockwise (CCW). Micro-particle image velocimetry (μPIV) and particle tracking velocimetry results showed that a bacterial cell of ∼ 2.75 μm long, rotating at 5.75 ± 0.39 Hz in a counterclockwise direction could generate distinct micro-vortices with circular flow fields with a mean velocity of 4.72 ± 1.67 μm/s and maximum velocity of 7.90 μm/s in aqueous solution. We verified our experimental data with a numerical simulation at matched flow conditions, which revealed vortices of similar dimensions and speed. We observed that the flow-field diminished with increasing z-height above the plane of the rotating cell. Lastly, we showed that we could activate and tune rotational mixing remotely using strains engineered with proteorhodopsin, where rotation could be activated by controlled external illumination using green laser light (561 nm).