Laser Light Research Articles

Dynamics of Nonlinear Optical Losses in Silicon‐Rich Nitride Nano‐Waveguides

AbstractFree carrier absorption (FCA) is established to be the cause of nonlinear losses in plasma‐enhanced chemical vapor deposition (PECVD) silicon‐rich nitride (SRN) waveguides. To validate this hypothesis, a photo‐induced current is measured in SRN thin films with refractive indices varying between 2.5 and 3.15 when a C‐band laser light is illuminating the SRN films at various powers, indicating the generation of free carriers. Furthermore, nonlinear loss dynamics is, for the first time, measured and characterized in detail in SRN waveguides by utilizing high peak power C‐band complex shape optical pulses for estimation of free carrier generation (FCG) and free carrier recombination (FCR) lifetimes and their dynamics. Both FCG and FCR are found to decrease with an increase in the refractive index of SRN, and, specifically, the FCR lifetimes are found (92 ± 7) ns, (39 ± 3) ns, and (31 ± 2) ns for the SRN indices of 2.7, 3, and 3.15, respectively. Lastly, nonlinear losses in high refractive index SRN waveguides are demonstrated to be minimized and altogether avoided when the pulse duration reduced below the free carrier generation lifetime, thus providing a way of taking a full advantage of the large inherent SRN nonlinear properties.

Development of a dry powder formulation for pulmonary delivery of azithromycin-loaded nanoparticles.

The COVID-19 pandemic has raised concern regarding respiratory system diseases and oral inhalation stands out as an attractive non-invasive route of administration for pulmonary diseases such as chronic bronchitis, cystic fibrosis, COVID-19 and community-acquired pneumonia. In this context, we encapsulated azithromycin in polycaprolactone nanoparticles functionalized with phospholipids rich in dipalmitoylphosphatidylcholine and further produced a fine powder formulation by spray drying with monohydrated lactose. Nanoparticles obtained by the emulsion/solvent diffusion-evaporation technique exhibited a mean hydrodynamic diameter around 195-228nm with a narrow monomodal size distribution (PdI < 0.2). Nanoparticle dispersions were spray-dried at different inlet temperatures, atomizing air-flow, aspirator air flow, and feed rate, using lactose as a drying aid, resulting in a maximal process yield of 63% and an encapsulation efficiency of 83%. Excipients and the dry powder formulations were characterized in terms of morphology, chemical structure, thermal analyses and particle size by SEM, FTIR, DSC/TGA and laser light diffraction. The results indicated spherical particles with 90% at 4.06µm or below, an adequate size for pulmonary delivery. Aerosolization performance in a NGI confirmed good aerodynamic properties. Microbiological assays showed that the formulation preserves AZM antimicrobial effect against Staphylococcus aureus and Streptococcus pneumoniae strains, with halos above 18mm. In addition, no formulation-related cytotoxicity was observed against the human cell lines BEAS-2B (lung epithelial), HUVEC (endothelial) and HFF1 (fibroblasts). Overall, the approach described here allows the production of AZM-PCL nanoparticles incorporated into inhalable microparticles, enabling more efficient pulmonary therapy of lung infections.

Rod-shaped LuAG:Ce transparent ceramic enabling ultrahigh forward efficiency for laser lighting in a transmissive mode.

Ceramic phosphors have high thermal conductivity and high thermal stability, showing great potential for use in laser lighting. However, it is difficult to further improve the forward efficiency in transmissive mode because of the arbitrarily emitting ceramic phosphors and light loss by secondary optical components. Here, an effective design of rod-shaped LuAG:Ce transparent ceramics was proposed, and the silicone encapsulated ceramic-based devices could operate stably under 3.5 W laser excitation, possessing a luminous efficiency of 150-180 lm/W, far exceeding the level of existing commercial transmissive mode. Besides, because of the gradual absorption of blue light and the gradient distribution of heat, the rod-shaped LuAG:Ce transparent ceramics could bear a power density of 46 W/mm2 without luminous saturation, and the thermal-induced luminous degradation only accounted for 7% under a 15 min operation. The ceramic-based laser lighting sources with low divergence angle (∼4°) and uniform spatial distribution were obtained. Our optimized transparent ceramic rod and encapsulation scheme provided a solution to improve the efficiency of a transmissive mode for laser lighting.

Silicon-based quantum random number generator with untrusted sources and uncharacterized measurements

Random numbers are essential resources in science and engineering, with indispensable applications in simulation, cybersecurity, and finance. Quantum random number generators (QRNGs), based on the principles of quantum mechanics, ensure genuine randomness and unpredictability. Silicon photonics enables the large-scale deployment of integrated QRNGs due to its low cost, miniaturization, and compatibility with CMOS technology. However, current integrated QRNGs are typically based on perfect or partially perfect device models, deviating from real-world devices, which compromises the unpredictability of quantum random numbers. In this study, we implemented a silicon-based QRNG that makes no assumptions about the source and only uses trusted but uncharacterized measurement devices. In experimental demonstration, we show that our setup can generate secure random numbers with different choices of intensities of laser light, and achieve an optimized random number generation rate of up to 4.04 Mbps. Our work significantly advances the security, practicality, and commercial development of QRNGs by employing imperfect devices.

A Review of the Application of the Laser-Light Backscattering Imaging Technique to Agricultural Products

Growing concerns about food safety and waste have increased consumer demand for high-quality agricultural products, particularly at the postharvest stage. This demand has prompted the development of non-destructive methods to assess or inspect the internal quality of fruits and vegetables. The backscattering imaging technique, also known as diffuse reflectance imaging, is considered a highly promising approach. Numerous studies have focused on practical applications, using laser light at selected wavelengths to develop quick multispectral methods. Due to the rapid interaction of photons with biological tissue, together with the highly computational performance of machine vision, backscattering imaging can offer a valuable alternative to traditional methods. Its primary benefits include quick measurements without chemical sample preparation, easy integration with high-throughput automatic quality control, and reduced waste, since this non-destructive technique does not damage samples. This review presents a comprehensive overview of backscattering imaging, including the measurement geometry, data analysis, and design considerations for vision systems. Additionally, it explores this technique’s advantages, challenges, and accuracy, as demonstrated using various case studies.

Laser Aggregometry Assessment of Blood Microrheology in a Slit Fluidic Channel Covered With Endothelial Cells.

The blood rheology in vitro in glass or plastic microfluidic chips is different from that in vivo in blood vessels with similar geometry. Absence of vascular endothelium is suggested to cause these discrepancies. This work aims to perform in vitro measurements of blood microrheologic parameters in a slit microfluidic channel covered with endothelial cells (HUVEC). The laser aggregometry was employed to measure the intensity of laser light, backscattered from the blood flow, as a function of shear stress to evaluate the hydrodynamic strength of red blood cells (RBC) aggregates in terms of critical shear stress (CSS). The results demonstrated a decrease in CSS accompanied by an increase in the accuracy of its measurement at similar shear stresses when endothelial cells were present in the channel. The findings hold valuable implications for advanced approaches for endothelization of microfluidic devices, facilitating the study of blood flow dynamics in physiologically more relevant environment.

Nanosecond-Lived Excimer Observation in a Crystal of a Rhodium(I) Complex via Time-Resolved X-ray Laue Diffraction.

The rare observation of transient Rh···Rh excimer formation in a single crystal is reported. The estimated excited-state lifetime at 100 K is 2 ns, which makes it the shortest-lived small-molecule species caught experimentally using the laser-pump/X-ray-probe time-resolved Laue method. Upon excitation with 390 nm laser light, the intermolecular Rh···Rh distance decreases from 3.379(4) to 3.19(1) Å, and the metal-metal contact gains more bonding character. On the basis of the experimental results and theoretical modeling, the structural changes determined with 100 ps time resolution reflect principally the S0 → S1 electronic transition.

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.

Multi-line laser 3D reconstruction method based on spatial quadric surface and geometric estimation

The traditional multi-line laser 3D reconstruction is based on binocular epipolar constraints and the equation of the laser optical plane. Firstly, matching points are identified based on the epipolar constraints. Then, the correct matching points are selected based on the optical plane equation of the multi-line laser. Finally, 3D reconstruction is performed using the selected matching points. In actual production processes involving multi-line lasers, noticeable distortion occurs due to the projection of Diffractive Optical Elements (DOE) at a large angle. This results in curved laser light planes and curved reflections on the measured objects. Under such circumstances, efficiently screening matching points using the traditional method based on the laser plane equation becomes challenging. Additionally, inherent noise in multi-line laser systems introduces errors in extracted laser center coordinates, making it impossible to directly obtain high-precision 3D data. To address these issues, this paper proposes a method that utilizes spatial quadric surfaces and geometric estimation for completing multi-line laser 3D reconstructions. By analyzing the distortion principle of DOE and the positional relationship after optical diffraction, the multi-line laser manifests as a quadric surface on the optical output plane. Consequently, by calibrating the equations of the quadric surface and applying binocular polar constraints, suitable matching points for the multi-line laser can be chosen. Once an accurate matching point is identified, a minimum geometric distance estimation can be established based on the distance constraint between the point and its corresponding epipolar line. This distance represents the separation between the left and right camera’s laser center points and their respective epipolar lines. Utilizing this estimate of the minimum geometric distance, a refined calculation can be performed to better satisfy epipolar constraints and obtain new matching points. Ultimately, utilizing these new matching points enables the completion of 3D reconstruction for multi-line lasers. In comparison with methods relying on spatial plane and epipolar constraints, our algorithm exhibits a superior degree of matchability and accuracy.According to multiple groups of test data, the average error before optimization is 0.3126 mm, and can be increased to 0.0336 mm after optimization.

Non-destructive detection of fructose solutions via Terahertz spectroscopy enhanced by Frequency Selective Surface (FSS)

Terahertz (THz) spectroscopy, combined with Frequency Selective Surfaces (FSS), is emerging as a powerful non-destructive technique for detecting and analysing the properties of biological samples. In this study, we explored the use of THz spectroscopy for detecting fructose solutions with concentrations ranging from 0.2 % to 10 %. Using femtosecond laser light sources, the THz transmission and absorption characteristics of fructose were investigated. The integration of FSS significantly enhanced the sensitivity of THz detection, yielding a 16 % improvement at 1.29 THz and 28 % at 1.67 THz. UV–Vis and Fourier Transform Infrared (FTIR) spectroscopy were employed to compare results with traditional methods, highlighting the superior sensitivity of THz spectroscopy, especially at low concentrations. The findings suggest that THz spectroscopy, enhanced by FSS, has strong potential for advancing non-invasive testing in biological and environmental applications.

A New Approach Toward Extreme Thermal Stability of Femtosecond Laser Induced Modifications in Glasses

AbstractImprinting thermally stable transformations by femtosecond laser in glass would benefit the development of optical sensors dedicated to harsh environments including combustors, nuclear reactors, aircraft engines, or metal/ceramic manufacturing processes. While glass brings undeniable assets over refractory crystalline materials like shaping ability (e.g., optical fiber form), one key challenge is to prevent the erasure of induced transformations at high temperatures and for long periods. In this article, the role of glass composition and viscosity to achieve modifications stable at high temperatures is first reviewed, providing a comprehensive roadmap for engineers in optics and photonics. While silica appears to be the candidate of choice, it is revealed that binary aluminosilicates can compete and sometimes surpass it. The hypothesis is formulated and investigated that a hybrid glass‐crystalline nano‐structuring can imprint ultra‐stable modifications inside glass. Laser‐induced modifications in Al2O3‐SiO2 and ZrO2‐Al2O3‐SiO2 glasses reveal a partial crystallization, shaped into a lamellar structure and orientable with laser light polarization. These birefringent structures can withstand temperatures up to 1300 °C for 30 minutes. Even after erasure, a positive index contrast persists, up to 1650 °C for binary 60Al2O3‐40SiO2 (mol%). This is the first observation of this kind of persisting index contrast, paving the way to ultra‐stable glass‐based optical waveguiding.

Laser L ight I nduced R etinopathy in a Young Boy: A Case Report from Eye Care Hospital, Karachi

A case report of a 14 year-old-boy who came with a history of direct gazing to laser pointer at Khairun'nisa Eye Hospital, Karachi. A comprehensive eye examination including Slit lamp biomicroscopy, Fundoscopy, optical coherence tomography and Fundus photography was done. Main outcome measure were right eye foveal scarring with normal periphery. Fundoscopy showed right Eye old scar at fovea, exactly like solar retinopathy. Solar retinopathy is a type of retinopathy which is caused by directly looking at sunlight. In this report we are presenting the classical case of retinopathy exactly like solar retinopathy due to gazing directly at laser light for a long period of time.

Evaluation and analysis of the electro-optic effect and the Stark effect in electro-optic polymers by the simple transmission measurement technique without an aperture

A simple and reliable transmission measurement technique without an aperture was utilized to evaluate both the electro-optic (EO) effect and the Stark effect of EO polymers. For some EO polymers, both the EO effect and the Stark effect were evaluated using laser light sources with various wavelengths of 1550 nm, 1308 nm, 980 nm, and 640 nm and the analysis method was also described. We showed that both the magnitude and the phase of the modulated light signal in lock-in detection at both the π/2 and 3π/2 points are very important for appropriate analysis.

Simultaneous influences of hematocrit in the erythrocyte medium on erythrocyte aggregation and sedimentation: a kinetic study by a laser scattering technique

The erythrocyte aggregation is an important physiological phenomenon in the circulation of blood. It is a basic characteristic of normal blood that plays a major role in the cardiovascular system, especially in the microcirculation. This study explained the kinetics of single cells rouleaux formation one- dimensional aggregate and three- dimensional aggregate, during simultaneous, and the effect of hematocrit on the process of aggregation and sedimentation. The present study was done on forty one healthy subjects. Laser light is passed through a well mixed sample of blood and the forward scattered light intensities recorded continuously. The samples were prepared with different hematocrit, (10%, 15%, 20%, and 25%). Increasing the hematocrit, (10%, 15%, 20%, and 25%) had significantly decreased the rate of rouleaux formation (P&lt; 0.005) but increase in the rate of one and three dimensional aggregate formation. On the other hand the sedimentation rate is decreased significantly (P

Assessment of microplastic exposure in nasal lavage fluid and the influence of face masks

Microplastics (MPs) can enter the human body through respiration and pose a hazard to human health. Wearing masks has become a routine behavior during the COVID-19 pandemic. The level of respirational exposure and the influence of wearing masks are currently unknown. We recruited 113 college students and divided them into natural exposure (NE), surgical mask (SM), and cotton mask (CM) groups. Nasal lavage fluid (NLF) was collected and MPs characteristics were analyzed using polarized light microscopy and laser direct infrared system. We found a relatively high abundance of MPs in NLF in the SM group (41.24 ± 1.73 particles/g). The particle size distribution and fibrous MP percentage significantly differed among the three groups. The main components in the NE, SM, and CM groups were polypropylene (58.70 %)，polycarbonate (PC, 49.49 %)，and PC (54.29 %). Components such as polyamide, polyethylene and polyethylene terephthalate were also detected. Wearing surgical masks increased the MP abundance in NLF (β = 0.36, P < 0.01). As the wear time increased, the abundance of MPs also rose (β = 0.28, P < 0.05). However, those who used bedding containing synthetic fibers had lower MP abundance in their NLF. This study highlights the use of NLF to evaluate MP exposure, which is associated with potential health risks.

Stearic Acid as Polymerization Medium, Dopant and Hydrophobizer: Chemical Oxidative Polymerization of Pyrrole.

In recent years, fatty acids have garnered significant attention as a natural phase-change material and a hydrophobizer due to their biocompatibility and biodegradability. In this study, the utilization of fatty acid is proposed as a polymerization medium for the first time. As a specific reaction, chemical oxidative polymerizations of pyrrole is conducted using ferric chloride as an oxidant in a stearic acid medium. The polymerizations resulted in the production of micrometer-sized polypyrrole (PPy) grains, which are aggregates of atypical primary particles with submicrometer size. The PPy grains are doped with stearic acid, suggesting that the stearic acid functioned as a dopant and a hydrophobizing agent as well as a polymerization medium. The dried PPy grains can adsorb at the air-water interface and function as a liquid marble stabilizer with light-to-heat photothermal properties. The liquid marble can move on a planar air-water interface by Marangoni flow induced by NIR laser light irradiation.

Growth of dendritic CuS nanostructures for photoacoustic image guided Chemo-Photothermal therapy

Herein, we report a unique method for design and development of carboxyl enriched dendritic CuS nanostructures (CuS NSs) for photoacoustic image guided chemo-photothermal therapy. The dendritic network was grown on the surface of CuS nanoparticles via layer-by-layer assembly of amino acid. XRD and TEM studies established the formation of crystalline well-spherical nanosized hexagonal covellite (CuS) phase. The successful growth of dendritic structure was apparent from the rise in surface charge, hydrodynamic diameter and characteristic vibrational band intensity of peptide bonds. The developed different generations of dendritic CuS NSs (D0-CuS NSs, D1-CuS NSs, D2-CuS NSs and D3-CuS NSs) displayed wide-ranging absorption band in near infrared (NIR) zone and exhibited good photothermal heating efficacy upon irradiation of 980 nm laser light. From in to vitro cellular studies, it has been found that the NIR irradiation effectively enhanced the photothermal toxicity of D3-CuS NSs towards cancer cells. Moreover, these negatively charged water-dispersible D3-CuS NSs were conjugated with positively charged anticancer drug, doxorubicin hydrochloride (DOX) through electrostatic interaction. The DOX loaded D3-CuS NSs (DOX@D3-CuS NSs) revealed pH dependent drug release behaviour and their considerable uptake in breast cancer cells (MCF-7). Further, DOX@D3-CuS NSs exhibited a much higher toxicity towards cancer cells upon NIR light over individual counterparts suggesting their strong ability for chemo-photothermal therapy. Moreover, these biocompatible CuS NSs have shown excellent concentration dependent photoacoustic properties at pulse laser excitation (850 nm) and thus, they can be found potential application in chemo-photothermal therapy.

Perilla oil emulsions stabilized by casein-dextran sulfate nanocomplexes with and without curcumin

Protein-polysaccharide nanocomplexes are potential particulate emulsifiers to improve physical and chemical stability of emulsions containing polyunsaturated fatty acids. This study prepared nanocomplex dispersions with 2.0 % w/v sodium caseinate and 0–0.4 % w/v dextran sulfate (DS) with and without 0.1 % w/v curcumin. The dispersions exhibited a Z-average diameter of 124.61–182.46 nm, a polydispersity index of 0.37–0.52, and a zeta potential between −30.1 and −34.9 mV, with a curcumin encapsulation efficiency of higher than 75 %. These nanocomplexes were used to emulsify 60 % v/v perilla oil (PO) through shear homogenization and sonication. Emulsions showed discrete droplets in light and confocal laser scanning microscopy. The creaming index decreased as DS concentration increased, remaining below 6 % after 30 days of storage Emulsions had >70 % DS, >80 % caseinate, and 100 % curcumin adsorbed on the oil droplet surface. For oxidative stability at 55 °C for 15 days, emulsions prepared with 2.0 % w/v caseinate and 0.4 % w/v DS, with and without curcumin, showed a maximum of 40 % reduction in the peroxide value and 71 % reduction in the thiobarbituric reactive substances value from those of bulk PO. The present study showed the significance of casein-DS nanocomplexes for the physical and chemical stability of PO emulsions.

Deep learning based x-ray spectrometer for high repetition rate characterization of betatron radiation

Betatron radiation produced from a laser-wakefield accelerator is a broadband, hard x-ray (&amp;gt;1 keV) source that has been used in a variety of applications in medicine, engineering, and fundamental science. Further development and optimization of stable, high repetition rate (HRR) (&amp;gt;1 Hz) betatron sources will provide a means to extend their application base to include single-shot dynamical measurements of ultrafast processes or dense materials. Recent advances in laser technology used in such experiments have enabled increases in shot-rate and system stability, providing improved statistical analysis and detailed parameter scans. However, unique challenges exist at high repetition rate, where data throughput and source optimization are now limited by diagnostic acquisition rates and analysis. Here, we present the development of a machine-learning algorithm for the real-time analysis of betatron radiation. We report on the fielding of this deep learning algorithm for online source characterization at the Institut National de la Recherche Scientifique's Advanced Laser Light Source. By fine-tuning an algorithm originally trained on a fully synthetic dataset using a subset of experimental data, the algorithm can predict the betatron critical energy with a percent error of 7.2 % with a reconstruction time of 1.5 ms, providing a valuable tool for real-time, multi-objective optimization at HRR.

Review on Grounds state Hanle effect on paraffin coated alkali atoms under condition EIT and EIA

IntroductionThis review is specifically aimed at a higher level of understanding of the ground-state Hanle effect through novel methods of atomic vapor interaction with resonant light. Electromagnetically Induced Transparency (EIT) and absorption (EIA) are the primary phenomena in this context. EIT is a process in which destructive interference at absorption frequencies within a medium is caused by a control laser and makes the medium clear to the probe laser light. It should be noted that this transparency is crucial for turning on/off the light pulses, slowing down or stopping in several cases, thus enhancing the effectiveness of atomic magnetometers. However, constructive interference that occurs in EIA raises the density of the medium, which is advantageous for profit-making precise measurements and the improvement of atomic clocks. ObjectiveThe objective of this study is to review the fundamental principles of the Hanle effect, EIT, EIA, and coating methods for alkali atoms. These principles and techniques are critical for improving the sensitivity and functionality of atomic magnetometers and other quantum devices. By understanding and leveraging these phenomena, significant progress has been made in the development of high-precision measurement tools and quantum technologies. ResultsAdvancements in atomic magnetometer sensitivity represent a rapidly growing area of interest, driving significant progress in the development of quantum devices. This review consolidates the existing knowledge and recent findings, offering a thorough understanding of the fundamental principles and practical applications of the Hanle effect, EIT, EIA, and coating methods for alkali atoms. This review highlights how advancements in EIT and EIA have contributed to the sensitivity improvements of atomic magnetometers, and underscores the importance of coating methods for maintaining system integrity and performance. These developments are essential to the evolution of modern quantum technologies and precision measurement devices.