Violet Laser Research Articles

Study the Optical Properties of Polyvinyl Alcohol / Methyl Red Composite Irradiated by Violet Laser

Study the Optical Properties of Polyvinyl Alcohol / Methyl Red Composite Irradiated by Violet Laser

III-nitride m-plane violet narrow ridge edge-emitting laser diodes with sidewall passivation using atomic layer deposition

A novel deep-ridge laser structure with atomic-layer deposition (ALD) sidewall passivation was proposed that enhances the optical characteristics of 8-µm ridge width III-nitride violet lasers on freestanding m-plane GaN substrates. The internal loss was determined using the variable stripe length method, where the laser structure with ALD sidewall passivation showed lower internal loss compared to the conventional shallow-ridge laser design. ALD sidewall passivation plays a critical role in device improvements; compared to the lasers without ALD sidewall passivation, the lasers with ALD sidewall passivation yield improved optoelectrical performance and longer lifetime under continuous-wave operation at high current density. This work demonstrates the importance of ALD sidewall passivation to laser performance, which enables high energy efficiency.

Laser-induced fluorescence spectroscopy of certain essential oils by blue and violet diode laser excitation

Laser-induced fluorescence (LIF) spectroscopy of 8 essential oils (rosemary, basil, orange, lavender, peppermint, rose, pomegranate and tea tree oil) has been performed using compact blue and violet lasers operating at 447 nm and 405 nm respectively. The various features of the obtained spectra and their possible molecular origins have been discussed. Important constituents in these oils have been identified, such as two types of chlorophylls (A and B), in addition to a type of tocopherol (vitamin E). It may be possible to roughly estimate, qualitatively, the relative abundance of these constituents in these essential oils. To the best of our knowledge, the analysis of a significant number of essential oils by laser induced fluorescence (LIF) technique has not been performed before. As a future application, the technique can be used for the efficient and rapid detection adulterants in essential oils.

Water‐Soluble Fluorescent Polymer Dyes with Tunable Emission Spectra for Flow Cytometry Applications

AbstractThe application of spectrally unique, bright, and water‐soluble fluorescent dyes is indispensable for the analysis of biological systems. Multiparameter flow cytometry is a powerful tool for characterization of mixed cell populations. To discriminate the different cell populations, they are typically stained by a set of fluorescent reagents, e.g., antibody‐fluorophore conjugates. The number of parameters which can be studied simultaneously strongly depends on the availability of reagents which can be differentiated by their spectral properties. In this study a series of fluorescent polymer dyes was developed, that can be excited with a single violet laser (405 nm) but distinguished by their unique emission spectra. The polyfluorene‐based polymers can be used on their own, or in combination with covalently bound small‐molecule dyes to generate energy transfer constructs to red‐shift the emission wavelength based on Förster resonance energy transfer (FRET). The polymer dyes were utilized in a biological flow cytometry assay by conjugating several of them to antibodies, demonstrating their effectiveness as reagents. This report represents the first systematic investigation of structure–property relationships for this type of fluorescent dyes.

Water-Soluble Fluorescent Polymer Dyes with Tunable Emission Spectra for Flow Cytometry Applications.

The application of spectrally unique, bright, and water-soluble fluorescent dyes is indispensable for the analysis of biological systems. Multiparameter flow cytometry is a powerful tool for characterization of mixed cell populations. To discriminate the different cell populations, they are typically stained by a set of fluorescent reagents, e.g., antibody-fluorophore conjugates. The number of parameters which can be studied simultaneously strongly depends on the availability of reagents which can be differentiated by their spectral properties. In this study a series of fluorescent polymer dyes was developed, that can be excited with a single violet laser (405 nm) but distinguished by their unique emission spectra. The polyfluorene-based polymers can be used on their own, or in combination with covalently bound small-molecule dyes to generate energy transfer constructs to red-shift the emission wavelength based on Förster resonance energy transfer (FRET). The polymer dyes were utilized in a biological flow cytometry assay by conjugating several of them to antibodies, demonstrating their effectiveness as reagents. This report represents the first systematic investigation of structure-property relationships for this type of fluorescent dyes.

Two‐Dimensional Characterization of Au/Ni/Thin Heavily‐Mg‐Doped p‐/n‐GaN Structure under Applied Voltage by Scanning Internal Photoemission Microscopy

The two‐dimensional characterization of the Au/Ni/thin p+‐GaN/n−‐GaN structure, which is a part of a junction barrier Schottky structure, is demonstrated by scanning internal photoemission microscopy (SIPM) method. In the SIPM photoyield image using a blue laser, small photocurrents based on the internal photoemission effect by electron injection across the metal/semiconductor interface (from Ni to GaN) are detected in the center of the electrode. On the periphery, large photocurrents in the opposite direction are detected. These currents are caused by the hole injection from Ni into p+‐GaN layer and the electrical field in the laterally extended depletion layer at the edge. By using a violet laser, large photocurrents based on the fundamental absorption generated in the depletion layer of the n−‐GaN layer are uniformly detected over the electrode. It is conformed that SIPM can be available for quasi‐three‐dimensional characterization of this structure.

A mechanical device to demonstrate the composition of two simple harmonic motions

The slot link mechanism can project uniform rotation to a simple harmonic motion (SHM), based on which, the device including two sliding table systems has been prepared. These two sliding table systems can be stacked up and down, and each of them can produce a tunable mechanical SHM using a stepper motor. When the upper sliding table system is attached to the lower one and both are turned on, the motion of the sliding table of the upper component is the composition of the two SHMs. With the help of a self-powered LED, a violet laser, and a movable phosphorescent foil, this mechanical device can visualize the composition of the SHMs in the same and mutual perpendicular directions including the beat phenomenon and Lissajous figures. In addition to demonstrating several typical compositions of two SHMs, this device can also highlight the vector characteristics of mechanical vibration and demonstrate the tilted Lissajous figures.

The violet laser irradiation influence on the dispersive properties of the PVA/MO composite thick

Polyvinyl alcohol (PVA) polymer, methyl orange (MO) and their composite was dissolved in water in order to prepare films with different thickness by casting method. The films were irradiated by a violet laser with a wavelength 405 nm for different times (0, 10, 20, 30 and 40) minute. The dispersion parameters were calculated before and after exposure to the laser using the Wemple–DiDomenico method. Dispersion energy (E d) and the single oscillator energy of electronic transition (E o) were increased with increasing the irradiating time for PVA, MO and PVA/MO thick films. This is useful to modify geometrical and optical specifications for materials which has many applications especially in the medical field. The Urbach energy also can be controlled by the irradiation times since it decreased with increasing the laser irradiation time which can be used to enhance the structure of the material.

High‐Speed GaN‐Based 405 nm Violet Superluminescent Diode with Tilted Facet for Visible Light Communications

Visible light communication (VLC) based on superluminescent diode (SLD) is a promising technology with great potential for future 6G optical wireless network. In this work, a 405 nm violet SLD device is fabricated with an 8° tilted facet at one end of the waveguide based on InGaN/GaN quantum wells. The device has an optical power of 14.67 mW under continuous‐wave operation. The full width at half maximum (FWHM) of the SLD at 400 mA is 12.52 nm, which is significantly larger than that in a violet laser diode (LD). Using the SLD as transmitter in VLC system, a high data transmission rate of 3.299 Gbps has been achieved using the discrete multiple tone (DMT) modulation. The corresponding bit error ratio (BER) is measured to be 1.67 × 10−3, which satisfies the forward error correction (FEC) threshold of 3.8 × 10−3. The results suggest that such device can be used as a promising light source for VLC and light fidelity (LiFi) applications.

PSX-9 Gonadectomy Is Not Correlated with Altered T-Lymphocyte Populations in Senior Labrador Retrievers

Abstract Retrospective studies have suggested that gonadectomies, such as the spays and neuters common in companion animal populations, may be correlated with the development of autoimmune conditions later in the life of an animale. This study investigated the potential influences of gonadectomy on peripheral blood lymphocyte populations through flow cytometry. Twenty senior Labrador Retrievers (10 males and 10 females) were randomly selected from Four Rivers Kennel’s existing research colony according to their intact or altered status. Groups were balanced by age and body weight (average 11.4 y/o and 64.5 kg) as both have been previously shown to alter lymphocyte populations. A single blood collection was performed and stained with canine cross-reactive conjugated antibodies CD3-FITC, CD4-Superbright 600, CD8-Superbright 702, and a fixable lime viability stain (Invitrogen, Waltham MA). Samples were processed through a whole blood based lyse no-wash method and analyzed on an Attune NXT Flow Cytometer equipped with blue and violet lasers (ThermoFisher Waltham, MA). Measurement of cell populations was completed on a defined volume of each sample, and all subsets were gated to live, singlet lymphocytes. Statistical significance was determined through one-way ANOVAs on JMP Pro 16 (Cary, NC). There were no significant differences in CD4+/CD8+ ratio between groups (P = 0.56), or total lymphocyte populations (P = 0.34). Additionally, there were no significant differences between groups regarding CD3+ MFI (P = 0.25), CD8+ MFI (P = 0.70), or CD4+ MFI (P = 0.43). Overall, in age and body weight balanced senior Labrador Retrievers, spay or neuter status did not significantly influence T-cell populations. This suggests that previous gonadectomy does not influence the adaptive immune system as an animal ages. Further research is needed to clarify the relationship between gonadectomy and the later development of autoimmune disorders.

Analysis of Microcystis aeruginosa physiology by spectral flow cytometry: Impact of chemical and light exposure.

M. aeruginosa fluorescent changes were observed using a Cytek Aurora spectral flow cytometer that contains 5 lasers and 64 narrow band detectors located between 365 and 829 nm. Cyanobacteria were treated with different concentrations of H2O2 and then monitored after exposure between 1 and 8 days. The red fluorescence emission derived from the excitation of cyanobacteria with a yellow green laser (550 nm) was measured in the 652-669 nm detector while green fluorescence from excitation with a violet laser (405 nm) was measured in the 532-550 nm detector. The changes in these parameters were measured after the addition of H2O2. There was an initial increase in red fluorescence intensity at 24 hours. This was followed by a daily decrease in red fluorescence intensity. In contrast, green fluorescence increased at 24 hours and remained higher than the control for the duration of the 8-day study. A similar fluorescence intensity effect as H2O2 on M. aeruginosa fluorescence emissions was observed after exposure to acetylacetone, diuron (DCMU), peracetic acid, and tryptoline. Minimal growth was also observed in H2O2 treated cyanobacteria during exposure of H2O2 for 24 days. In another experiment, H2O2-treated cyanobacteria were exposed to high-intensity blue (14 mW) and UV (1 mW) lights to assess the effects of light stress on fluorescence emissions. The combination of blue and UV light with H2O2 had a synergistic effect on M. aeruginosa that induced greater fluorescent differences between control and treated samples than exposure to either stimulus individually. These experiments suggest that the early increase in red and green fluorescence may be due to an inhibition in the ability of photosynthesis to process photons. Further research into the mechanisms driving these increases in fluorescence is necessary.

Study the Optical Properties of Polyvinyl Alcohol Thick Film Irradiated with Violet Laser

Background:
 The aims study of this work is the effect of violet laser beam irradiating on the optical properties of the Polyvinyl alcohol PVA before and after irradiation to a laser beam of different time 10, 20, 30 and 40 minute.
 Materials and Methods:
 The polymer powder PVA 0.008 mg was dissolved in 7 ml distilled water at temperature 40 °C and the thickness of the film was 3000 nm by using weight method to measure the thickness of the films. A semiconductor laser with a wavelength of 405 nm was used to irradiate the films.
 Results:
 The absorbance, transmittance and reflectance spectra of thick films before and after laser irradiation were plotted. The energy gap and optical constants were calculated.
 Conclusions:
 The irradiation with the violet laser causes a breakdown of the bonds, which causes a decrease in the absorbance and reflectance spectrum, while the energy gap increases.

Effect of Lipopolysaccharide on Development of <i>Aspergillus fumigatus</i> Biofilm on Nasal Epithelial Cells

Background and Objectives <i>Aspergillus fumigatus</i> is one of the common causes of fungal airway inflammatory diseases and lipopolysaccharide (LPS) acts as key regulator of airway inflammation. In addition, bacterial and fungal biofilm commonly coexist in chronic rhinosinusitis. In this study, we evaluated the effect of LPS on the development of <i>A. fumigatus</i> biofilm formation on the nasal epithelial cells.Materials and Method Primary nasal epithelial cells were cultured with <i>A. fumigatus</i> conidia with or without LPS for 5 days. The production of interleukin (IL)-6, IL-8, and transforming growth factor (TGF)-β1 from nasal epithelial cells was determined by enzyme-linked immunosorbent assay. The effects of LPS on <i>A. fumigatus</i> biofilm formation were determined using biofilm dry weight, and crystal violet, concanavalin A, safranin staining, and confocal scanning laser microscopy.Results LPS and <i>A. fumigatus</i> significantly enhanced the production of I L-6, I L-8, and TGF-β1 from nasal epithelial cells. <i.A. fumigatus</i> can form biofilm on primary nasal epithelial cells, and this significantly increased in a time-dependent manner when cocultured with LPS, the dry weight, concanavalin A, and safranin staining.Conclusion The exposure of <i>A. fumigatus</i> to LPS enhanced the formation of biofilms. The coexistence of LPS and <i>A. fumigatus</i> enhanced fungal biofilm formation and this may be associated with the development of recalcitrant airway inflammatory diseases.

Repurposing Selamectin as an Antimicrobial Drug against Hospital-Acquired Staphylococcus aureus Infections.

The emergence of multidrug-resistant strains requires the urgent discovery of new antibacterial drugs. In this context, an antibacterial screening of a subset of anthelmintic avermectins against gram-positive and gram-negative strains was performed. Selamectin completely inhibited bacterial growth at 6.3 μg/mL concentrations against reference gram-positive strains, while no antibacterial activity was found against gram-negative strains up to the highest concentration tested of 50 μg/mL. Given its relevance as a community and hospital pathogen, further studies have been performed on selamectin activity against Staphylococcus aureus (S. aureus), using clinical isolates with different antibiotic resistance profiles and a reference biofilm-producing strain. Antibacterial studies have been extensive on clinical S. aureus isolates with different antibiotic resistance profiles. Mean MIC90 values of 6.2 μg/mL were reported for all tested S. aureus strains, except for the macrolide-resistant isolate with constitutive macrolide-lincosamide-streptogramin B resistance phenotype (MIC90 9.9 μg/mL). Scanning Electron Microscopy (SEM) showed that selamectin exposure caused relevant cell surface alterations. A synergistic effect was observed between ampicillin and selamectin, dictated by an FIC value of 0.5 against methicillin-resistant strain. Drug administration at MIC concentration reduced the intracellular bacterial load by 81.3%. The effect on preformed biofilm was investigated via crystal violet and confocal laser scanning microscopy. Selamectin reduced the biofilm biomass in a dose-dependent manner with minimal biofilm eradication concentrations inducing a 50% eradication (MBEC50) at 5.89 μg/mL. The cytotoxic tests indicated that selamectin exhibited no relevant hemolytic and cytotoxic activity at active concentrations. These data suggest that selamectin may represent a timely and promising macrocyclic lactone for the treatment of S. aureus infections.

FRET causing misleading signal from fluorescein excited by the violet laser in flow cytometry.

Multiple immunolabeling introduces high risks of interferences between fluorescences. As an example, in analyzing T cell clonality, we recently reported a fluorescence resonance energy transfer (FRET) effect providing an unexpected signal on B770 (PE-Cy7) detector, on the Vβ-PE positive CD3 APC-Alexa750+ T cell subsets. Here, we report another FRET effect produced by the violet laser in Vβ-FITC positive CD3-Pacific Blue (PB) T cells providing signal on V550 (Krome Orange; KrO) detector. The study was performed on fresh whole blood, labeled with anti-CD3-PB, CD8-KrO, Vbeta FITC, Vbeta PE, CD4 AA750 then fixed, treated for erythrolysis, and washed before analysis on DxFlex cytometer from Beckman Coulter. Data were analyzed using Kaluza software. Using this panel, we repeatedly observed an added CD8dim-KrO (V550) cell population on all Vβ FITC positive T cells. The unexpected green signal excited by the violet laser was still observed after removing anti-CD8-KrO (FMO) but disappeared where either anti-CD3-PB or anti-Vβ-FITC was removed. The effect was also observed with an anti-TCR gamma delta-FITC labeling, but not with another FITC labeled antibody targeting a protein out of the CD3-TCR complex. The analysis of fluorochrome spectra confirms that PB emission and FITC excitation spectra partly overlap. This observation clearly reminds users that FRET can give misleading results in case of labeling of very close markers with complementary fluorochromes. This risk has to be considered in panel design. These observations clearly highlight the potential for FRET to give misleading results in cases where very close markers are labeled with complementary fluorochromes. This risk must be considered when designing panels. To our knowledge, this is the first description of a FRET between PB and FITC as acceptor thus excited by the violet laser.

Combined Effects of Ultraviolet Irradiation and Magnetic Field on the Properties of Dip-coated ZnO thin films

In this study, four ZnO thin films were deposited on FTO substrates using the sol–gel dip coating method to examine their microstructural, morphological, and optical properties through various techniques. Three of them were subjected to ultraviolet (UV) light, magnetic field (MF), and a combination of UV and MF during deposition, referred as ZnO: UV, ZnO: MF, and ZnO: (UV+MF), respectively. The results obtained showed that the simultaneous UV and MF exposure improved the crystallinity and surface homogeneity of the as-deposited film. Moreover, ZnO: (UV+MF) film exhibited an average transparency of 80% in the visible region and a high optical bandgap (3.67 eV). Room-temperature photoluminescence (PL) spectra revealed a weak UV emission and a strong violet emission peaks for all films. However, the violet emission intensity being lower in ZnO: UV and ZnO: MF films due to a reduction in zinc interstitials (Zni) defects, The simultaneous UV and MF exposure did not reduce Zni defects, and the violet emission intensity was almost identical to that of the untreated film. These findings suggest that the ZnO: (UV+MF) film can be a promising candidate for the development of ultraviolet and violet lasers and light-emitting diodes.

Single-frequency violet and blue laser emission from AlGaInN photonic integrated circuit chips.

Chip-based, single-frequency and low phase-noise integrated photonic laser diodes emitting in the violet (412 nm) and blue (461 nm) regime are demonstrated. The GaN-based edge-emitting laser diodes were coupled to high-quality on-chip micro-resonators for optical feedback and mode selection resulting in laser self-injection locking with narrow emission linewidth. Multiple group III-nitride (III-N) based photonic integrated circuit chips with different waveguide designs including single-crystalline AlN, AlGaN, and GaN were developed and characterized. Single-frequency laser operation was demonstrated for all studied waveguide core materials. The best side-mode suppression ratio was determined to be ∼36 dB at 412 nm with a single-frequency laser emission linewidth of only 3.8 MHz at 461 nm. The performance metrics of this novel, to the best of our knowledge, type of laser suggest potential implementation in next-generation, portable quantum systems.

Expanding panel size in spectral flow cytometry with StarBright Dyes excitable by the ultraviolet (355 nm), violet (405 nm), blue (488 nm) and yellow (561 nm) lasers.

Abstract The recently launched fluorescent dyes from Bio-Rad, StarBright Dyes, deliver tunable brightness and spectral properties, greater stability, improved lot-to-lot reproducibility, and spectral consistency. Specifically designed for multicolor flow cytometry with researchers needs in mind, StarBright Dyes address the common pain points in flow such as brightness, broad emission spectra, staining consistency, and ease-of-use, solving issues of signal resolution when constructing complex panels. These bright dyes have the additional benefit of a unique full spectral profile, making them ideal for inclusion in spectral flow cytometry, when creating multicolor panels. Here we present data of our newest additions to the StarBright range, the StarBright Blue and StarBright Yellow Dyes on a five-laser spectral cell analyzer. Both dye series are bright and allow expansion across the 488 and 561 lasers giving more dye choice for all panel sizes but are particularly useful when large panel design is required. In this study we show, when StarBright Blue and StarBright Yellow Dyes are combined with other members of the StarBright Dye range, polymer dyes and traditional fluorescent dyes, very large immunophenotyping panels can be constructed allowing identification of many peripheral blood subsets. In addition, novel dye combinations can be identified increasing the numbers of dyes and therefore markers identified from one sample. When combined with their ability to be fixed in both PFA based and alcohol-based fixatives, with minimal spectral changes, and to be pre-mixed for up to 33 days, the flexibility of StarBright Dyes means they are ideal for new and expanding existing panels regardless of the type of flow cytometer being used.

Antibacterial and Antibiofilm Efficacy of Copper-Doped Phosphate Glass on Pathogenic Bacteria.

the antibacterial activity was determined using microbroth dilution and time-kill assay. The antibiofilm activity was investigated using crystal violet and confocal laser scanning microscopy. Bacteria growing in absence of CDPG were used as controls. the MIC was ≥125 mg of CPDG/mL; the log10 CFU/mL reduction ranged from 2.66-3.14 to 6.23-9.65 after 4 and 24 h respectively. Generally, no growth was observed after 24 h of treatment with CDPG; the MBC was 250 mg/mL for L. casei and S. oralis while 500 mg/mL for the rest of the bacteria. The highest and lowest antibiofilm activity was observed against S. oralis and E. coli respectively. Three patterns of complete biofilm disruption were seen: (i) large areas with E. fecalis and S. oralis, (ii) medium-size pockets with S. aureus and P. aeruginosa, or (iii) small areas with E. coli and L. casei. CDPG can be potentially used as an antibacterial and an antibiofilm agent against oral biofilm-forming bacteria.

Violet Laser Treatment of Nitrogen-Doped Reduced Graphene Oxide Electrodes and KOH Electrolytes Containing p-Phenylenediamine for High-Performance Supercapacitors

The electrical conductivity and capacitive behavior of supercapacitors (SCs) were found to be improved by the synergistic effects of the violet laser treatment (VLT) of nitrogen-doped reduced graphene oxide (N-rGO) as an electrode and 1.5% (w/v) p-phenylenediamine (PPD)-containing KOH as a redox electrolyte. The SC employing VLT treatment on the N-rGO electrode with 2 M KOH (N-rGO-V) represented a greater specific capacitance of up to 263.6 F g–1 compared to N-rGO in the same electrolyte, which was 232.2 F g–1 at 0.25 A g–1. To further improve the charge-storage ability, the SC using the VLT treatment on the N-rGO electrode with the PPD addition into 2 M KOH (N-rGO-V-PPD) revealed the highest specific capacitance, reaching 593.7 F g–1 at 0.25 A g–1 or 28.6% compared to N-rGO in the same redox electrolyte (N-rGO-PPD). Furthermore, the capacitance retention after 10,000 cycles of N-rGO-V-PPD remained at 62% (265 F g–1 at 100 mV s–1), which is still significantly higher than that of other samples, and the VLT technique provided a lower self-discharge rate. According to the physical characterizations, N-rGO-V-PPD has a rougher and larger surface area due to the exfoliated graphene oxide sheets and has a modest increase in the number of quinone/carbonyl functional groups in the graphene material, resulting in better electrical conductivity. All of these could be contributing factors to the performance improvement. Lastly, PPD provides redox mediators such as H+ and e– in the redox electrolyte, which are anticipated to improve the charge storage.