Blue Laser Diodes Research Articles

Disposable Miniaturized Electrochemical Sensing Platform With Laser-Induced Reduced Graphene Oxide Electrodes for Multiplexed Biochemical Analysis.

Metabolic biomarkers, such as Dopamine (DA), Uric acid (UA), and Ascorbic acid (AA), have significant roles in determining the physiological functioning of the human body. These are often analyzed through clinical lab-based procedures which are bulky and require skilled technicians. In view of this, the design, development, and fabrication of a portable, cost-effective, user-friendly, and disposable device for electro-analytical detection, leading to point-of-care (POC) detection of these metabolic biomarkers is a pressing need. This work reports a laser-induced reduced graphene oxide (LIrGO) based miniaturized paper device fabricated by laser ablation of a lab-grade paper using a blue diode laser (450 nm). A three-electrode electrochemical platform was designed with the LIrGO electrodes, whereby bare rGO electrodes were employed as working and counter electrodes, and Ag/AgCl ink-coated rGO was used as the reference electrode. The device was characterized morphologically by Scanning Electron Microscopy (SEM) and electrochemically by a potentiostat. The prepared device was subjected to electrochemical sensing of Dopamine (DA), Uric Acid (UA), and Ascorbic Acid (AA). Furthermore, the effects of several sensory parameters, such as concentration, pH, and interference, were analyzed. A linear range of 10- [Formula: see text] was obtained for all three analytes with the limit of detection (LoD) being [Formula: see text], [Formula: see text], [Formula: see text], and the limit of quantification (LoQ) being [Formula: see text], [Formula: see text], [Formula: see text] for DA, UA and AA, respectively. Finally, the device was tested for non-interference with co-analytes and validated by testing a real sample of human blood serum. This work demonstrates a proof-of-principle of utilizing bare LIrGO for selective sensing which will open door to multiplexed and POC sensing.

Thermal effect analysis on cuboid Pr:YLF crystals pumped by blue laser diodes.

Using blue laser diodes (LDs) to pump Pr:YLF crystals can directly realize visible-band laser output. Compared with the traditional frequency doubling and LD direct output method, it has the advantages of simple design, compact structure, and high beam quality. For solid-state lasers, pump-induced thermal effects of gain media are the principal limiting factors for the desired high-power output. In this paper, internal temperature space model distribution of a rectangular cross-section Pr:YLF crystal is established. On this basis, the temperature distribution, thermal stress distribution, and thermal focal length variation of single-end pumped and double-end pumped laser crystals are analyzed. The results are verified by COMSOL simulations and experimental measurements. To our knowledge, this analysis is the first to examine the thermal effect of a rectangular cross-section Pr:YLF crystal, analyzing the limit power that the crystal can withstand, which paves the way for better performances of visible lasers with stable and high-power output.

Study on carrier transport in InGaN upper waveguide layer of GaN-based blue laser diodes

The carrier transport capacity of the unintentionally doped InGaN upper waveguide (UWG) layer affects the hole injection efficiency of GaN-based blue laser diode. In this article, we studied the carrier transport property of UWG layer grown under various conditions by metal organic CVD. Hole diffusion length in these samples were obtained by photoluminescence. It is found that higher diffusion length can be obtained with growth temperature around 840 °C–870 °C and V/III ratio about 16 000. It is also found that reducing the threading dislocation density can enhance the carrier transport capacity of the UWG layer. Finally, blue laser diodes (LDs) were fabricated to confirm that increasing the effective diffusion length of carriers in UWG layers can help improve LDs performance.

Wide Range CCT Laser-Based Illuminant With High Efficiency and Excellent Optical Performances

A wide range correlated color temperature (CCT) white light laser-based illuminant (LBI) consisting of dual blue laser diodes (LDs), yellow phosphor color converters and red LDs has been proposed. In addition to the conventional 455 nm blue LDs-pumped phosphor color converters, another blue LD is utilized for the adjustment of CCT and improvement of the color rendering index (CRI). Considering systematic manipulation of the power ratio of LDs and peak wavelength of tuning blue LDs from 440 nm to 480 nm, different combinations of spectral power distributions of LBIs were simulated. It shows that an optimized 465 nm tuning blue LD is employed to achieve a balance between optical performances and blue light hazard efficiency of radiation (BLHER). The first practical LBI comprised of Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> :Ce <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> (YAG:Ce <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> ) phosphor color converters and three monochromatic LDs of 455 nm, 465 nm and 635 nm was fabricated based on the stated simulations. In good agreement with the simulation results, the LBI has simultaneously achieved an excellent CRI beyond 85, a high luminous flux of approximately 2000 lm and a high luminous efficiency of radiation (LER) of over 300 lm/W at the fairly wide CCT range of 3300 K to 6000 K. The low BLHER was consistently below 0.237. The circadian action factor (CAF) was between 0.36 and 0.83, and its tunability was 2.31 above the CCT range, which favors the entrainment of circadian rhythm. Therefore, this work demonstrates a promising method for providing high-quality and human-oriented white light sources in applications requiring great brightness.

67‐2: Adoption of Blue Light Semiconductor Laser Diode (BLDA) in LTPS TFT Manufacturing

We have investigated adoption of CW blue laser diode annealing (BLDA) in manufacturing process of LTPS TFT backplane. Our experiments have shown that except crystallization annealing, BLDA can be adopted in dehydrogenation of precursor amorphous silicon film, and also can be used in the activation after ion implantation. By using BLDA dehydrogenation of H2 content as high as 20% can be implemented. In the activation, BLDA can achieve surface resistance much lower than using conventional RTA.

Speckle- and interference fringes-free illumination system with a multi-retarder plate.

Our study proposes a novel method for obtaining speckle-free homogeneous illumination using a combination of a multi-retarder plate, a microlens array, a Fourier lens, and a diffraction optical element (DOE) based on pseudorandom binary sequences. The proof-of-concept multi-retarder plate is introduced to generate multiple uncorrelated laser beams, while a mathematical model was developed to explain the method's mechanism and evaluate its effectiveness. In the DOE passive (stationary) mode, the method was found to reduce speckle contrast to 0.167, 0.108, and 0.053 for red, green, and blue laser diodes, respectively. In active mode, the speckle contrast was further reduced to 0.011, 0.0147, and 0.008. The observed differences in speckle contrast in the stationary mode were attributed to variations in the coherence lengths of the RGB lasers. By implementing the proposed method, we successfully generated a square-shaped illumination spot that was free from interference artifacts. The spot obtained exhibited a slow, weak variation in intensity across the screen, attributable to the multi-retarder plate's suboptimal quality. However, this limitation can be readily addressed in future studies through the adoption of more advanced fabrication techniques.

Simple and compact high-power continuous-wave deep ultraviolet source at 261 nm based on diode-pumped intra-cavity frequency doubled Pr:LiYF4 green laser.

We report the recent progress on diode-pumped high-power continuous-wave Pr:LiYF4 (YLF) green laser and deep ultraviolet (DUV) laser generation via intracavity frequency doubling. Using two InGaN blue diode lasers as pump source to form a double-end pumping geometry, in this work, we have demonstrated a green laser at 522 nm with a maximum output power of 3.42 W, which is believed to be the highest power ever achieved in all-solid-state Pr3+ lasers in this specific spectral region. Moreover, by intracavity frequency doubling of the achieved green laser, we have further obtained a DUV laser at about 261 nm with a maximum output power of 1.42 W, which is far higher than previous results. The watt-level 261-nm laser paves the way towards the realization of simple and compact DUV source for a variety of applications.

Effectiveness of katuk leaf chlorophyll (Sauropus androgynus (L) Merr) with blue and red laser a ctivation to reduce Aggregatibacter actinomycetemcomitans and Enterococcus faecalis biofilm

In this study, the efficacy of using Sauropus androgynus (L) Merr, a katuk leaf chlorophyll photosensitizer, to reduce Aggregatibacter actinomycetemcomitans and Enterococcus faecalis biofilm was investigated. A red and blue diode laser is used as the light source. The sample was split into four groups: a negative control group, a positive control group, a blue laser treatment group (B), and a red laser treatment group (R), both with and without the addition of katuk leaf chlorophyll 1.6 mg/ml, and with varying densities of laser energy exposure of 2.5 J/cm2, 5 J/cm2, 7.5 J/cm2, and 10 J/cm2. Laser exposure and chlorophyll photosensitizer were tested using ELISA and ANOVA. At an energy density of 10 J/cm2, the optimal bacterial mortality rate was obtained in each treatment group. Namely, in the Aggregatibacter actinomycetemcomitans biofilm, the negative group, the number of deaths was 73.30% using a blue diode laser and 63.25% using a red diode laser. In the positive group, the number of deaths was 86.12% using a blue diode laser and 83.29% using a red diode laser. In the Enterococcus faecalis biofilm, in the negative group, the number of deaths was 67.78% using the blue diode laser and 75.33% using the red diode laser, and in the positive group, the number of deaths was 71.71% using the blue diode laser and 86.41 using a red diode laser. Exposure to blue and red diode lasers activates chlorophyll in katuk leaves, killing bacteria and reducing biofilms.

A new smart laser photoluminescent light (LPL) technology for the optimization of the on-street lighting performance and the maximum energy saving: development of a prototype and field tests

Lighting demand in built environments corresponds to more than 10% of the global energy use, with great potential for energy saving thanks to innovative smart materials and combination of passive–active strategies. This paper focuses on an innovative smart lighting system based on a blue-diode laser technology combined with photoluminescent pavements, to obtain a self-lighting surface with a substantial reduction in electricity consumption. A laser variable angle scanner prototype was developed and operated through a dedicated management software. The prototype was installed in lab to measure the emitted luminance/illuminance of the pavement, its time decay, and the electricity consumption. This application is yet a prototype, the scanning area and the investigated pavement are more compatible with pedestrian street and sidewalk because of the lower illuminances to be maintained. The results were compared to standard solutions installed in typical roads. The results presented promising benefits in terms of electricity saving (about 40% compared to standard LEDs) and luminance uniformity (higher than 0.9 compared to standard systems, i.e. 0.17÷0.33). Important future ideas derive from preliminary experimental campaigns to improve the smart laser system, and the coupled pavement properties to reduce the consumptions and improve the lighting conditions for pedestrians and vehicles, within potential self-lighting streets.

Laser-induced in situ synthesis of nano-composite Co–Co3O4–rGO on paper: miniaturized biosensor for alkaline phosphatase detection

Recent progress in the in situ synthesise of various nanomaterials has gained tremendous interest and wide applications in various fields. For the first time to the best of our knowledge, this work reports a methodology of ultra-fast in situ synthesis of cobalt–cobalt oxide-reduced graphene oxide (Co−Co3O4−rGO (CC–rGO)) composite by laser ablation. The photothermal reduction technique was leveraged to develop the CC–rGO. For this, a low-cost 450 nm blue diode laser was irradiated onto a grade 1 filter paper in the presence of cobalt ions readily patterns the carbon matrix of paper to the composite material. Moreover, the variation of cobalt concentrations from 0.1–0.5 M led to structural and morphological changes. Standard techniques were adopted for thorough characterizations of developed sensor material for conductivity analysis, specific surface area, crystal-structural information, surface morphology, and chemical composition. The observed results were highly promoting towards the electrochemical sensing applications. Further, the developed sensor was found to be highly selective toward detecting a vital bio analyte alkaline phosphatase (ALP). The sensors performance was highly significant in the linear range of 10–800 mU l−1 with a detection limit of 10.13 mU l−1. The sensors applicability was further validated in actual human serum samples via a recovery-based approach. In the future, the developed in situ material methodology can begin a rapid composite material synthesis at a larger scale.

Electron Trapping Optical Storage Using A Single‐Wavelength Light Source for Both Information Write‐In and Read‐Out

AbstractIn conventional electron trapping optical storage phosphor, both short‐ and long‐wavelength light are needed for information write‐in and read‐out, respectively, complicating the optical storage system. Here, a Y3Al2Ga3O12:Pr3+,Eu3+ optical storage phosphor with Pr3+ as an electron donor and Eu3+ as an electron trap is designed, and a single wavelength write‐read scheme is demonstrated, which employs the same blue laser diode (LD) light source for both optical write‐in through two‐photon up‐conversion charging and for read‐out based on photostimulated luminescence (PSL), originated from 4f15d1→4f2 transition of Pr3+ peaked at 315 nm in UV region. A deep electron trap with the mean depth of 1.42 eV and a narrow distribution of 0.3 eV is observed in the presence of Eu3+ in Y3Al2Ga3O12:Pr3+, implying its long‐term storage potential. The write‐in and read‐out experiments are conducted using 450 nm blue LD light with the power density of 1 W cm−2 for write‐in and that with a low power density of 0.02 W cm−2 for read‐out in order to avoid the effect of up‐conversion luminescence on PSL signal. These results will advance the electron trapping optical storage scheme.

20.4: Activation of Doped Silicon Film Using Semiconductor Blue Light Diode Laser Annealing

We have investigated activation annealing of the doped poly silicon film of LTPS TFT by using CW semiconductor blue light diode laser. It has been found that by full melting and re‐crystallization, the sheet resistance can be reduced significantly to 1/3 of which can be realized by using conventional RTA treatment. We will report the experiment results in the paper.

Pump Excited-State Absorption at 442 ± 1 nm for Efficient Visible Fluoride Fiber Lasers

In the well-known excited-state absorption (ESA) process, population inversion of the laser transition can be achieved by a strong pump ESA involving a lower laser level. The exploitation of pump ESA has expanded from the visible to the near-infrared spectral range, based on various laser sources. Extending the operating wavelength of the pump ESA is greatly significant for the development of rare-earth-doped fluoride fiber lasers. Herein, we report, presumably, the shortest operating wavelength of pump ESA at 442 ± 1 nm for an efficient continuous-wave visible fluoride fiber laser. A novel scheme for direct blue diode pumping was proposed and demonstrated in an Ho <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped fluoride fiber. Utilizing a 442 ± 1 nm blue laser diode, single-wavelength ground-state absorption (GSA) and ESA pumping mechanism were investigated not only for double populating of the upper laser level by GSA and ESA, but also to depopulate the lower laser level by ESA. We report a slope efficiency of 50.3% with respect to the launched pump power of 442 ± 1 nm and an output power of up to 327 mW for a 750 nm fiber laser. This result is an order of magnitude higher than that previously reported for a directly blue-diode-pumped deep-red Ho <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped fluoride fiber laser. Moreover, the numerical modeling results were in good agreement with the experimental results. Our approach represents a significant advancement for blue pump ESA in visible fluoride fiber lasers, which opens new capabilities for blue-diode pumping for a wide range of future applications.

Vigorous high-efficiency YAGG:Ce phosphor-in-glass film for next-generation laser lighting applications

It is an important challenge to select suitable color converters and apply them to laser diodes (LDs) lighting field. Sapphire plates are used as substrates for phosphor-in-glass films (PiFs) due to their ultrahigh thermal conductivity (∼ 30 W m−1 K−1). Herein, Y3Al3.5Ga1.5O12:Ce3+ (YAGG:Ce) phosphor mixing silicate glass powder is successfully sintered on sapphire plates to fabricate YAGG:Ce phosphor-in-glass film (PiF). The microstructure appearance and photoelectric characteristics of the efficient green color converter are studied in detail. In addition, it is worth noting that the maximum internal quantum efficiency of the prepared PiF is 92%, which is close to that of the original phosphor (98%). Meanwhile, the saturation threshold of YAGG:Ce PiF reaches 38.96 W/mm2 with luminous efficiency (LE) of 230.85 lm/W under the excitation of 460 nm blue LD. Notably, PiF has ultra-high power density while still maintaining such high LE. In order to highlight the application of this color converter in laser lighting, we assemble laser flashlights and fireflies lights. The test of the laser flashlight shows excellent performances such as high brightness, strong focusing effect and wide irradiation range. All indications manifest that YAGG:Ce PiF is an excellent green color converter.

Composition and luminescence properties of highly robust green-emitting LuAG:Ce/Al 2O 3 composite phosphor ceramics for high-power solid-state lighting

The major advantage of laser lighting over white light-emitting-diode is the possibility to achieve ultra-high luminance. However, phosphors usually suffer laser-induced luminescence saturation, which limits the peak luminance of laser lighting devices. The aim of the present study is to develop LuAG:Ce/Al₂O₃ composite ceramics (LACCs) with a high saturation threshold for high-luminance laser lighting. Owning to the rigid crystal structure, proper synthetic process, and optimized thermal design, the LACCs possess small thermal quenching (16% loss in luminescence at 225 ℃), high quantum yield (&gt; 95%), and excellent luminescence properties. When the LACCs are irradiated by blue laser diodes in a reflection mode, a high luminous flux of 4634 lm and luminous efficacy of 283 lm·W⁻¹ are realized. Furthermore, they show no sign of luminescence saturation even when the power density reaches 20.5 W·mm⁻². With these favorable properties, the designed LACCs show great potential in high-luminance laser lighting.

Antibacterial potential of riboflavin mediated blue diode laser photodynamic inactivation against Enterococcus faecalis: A laboratory investigation.

This study aimed to evaluate the inactivation potency of riboflavin-mediated blue diodelaser photodynamic inactivation (PDI) against Enterococcusfaecalis at planktonic and biofilm stages and also investigated itseffect on the tooth color change. The antibacterial and antibiofilm activities of riboflavin mediated PDI against E.faecalis were investigated. The numbers of colony-forming units (CFUs)/mL were calculated. Teeth discoloration were evaluated using the CIE L*a*b* based color difference (ΔE). Antibacterial analysis indicated that the blue diode laser irradiation at 12, 18, 24, and 30J/cm2 alone and different concentrations of riboflavin solution (6.25 to 100μM) reduced the number of CFU/mL of E.faecalis, but the reduction was not statistically significant (P>0.05). Depending on the riboflavin concentration and the light dose, there can be as much as a 1-log effect on CFU/mL. In addition, E.faecalis biofilmwas more affected with 30J/cm2 irradiation dosage and 100μM riboflavin than other groups. Meanwhile, bacterial suspensions treated with 5.25% sodiumhypochlorite (NaOCl) showed maximum biofilm inhibition and colony number reduction, compared with the control. The teeth exhibited clinically acceptable color change after riboflavin treatment at concentrationranging from 6.25 to 50μM (ΔE < 3.7). The riboflavin mediated PDI process is somewhat less effective than NaOCl but perhaps less toxic to tissues. It might be feasible to repeat the riboflavin+light treatment to further promote efficacy.

Screening of Broadband Near-Infrared Cr3+-Activated Phosphors Using Ce3+ as a Probe

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) are ideal miniaturized NIR light sources, but it is still difficult to find broadband-emitting NIR phosphors due to the lack of appropriate material design principles. In this work, we propose a method to find hosts yielding broadband NIR Cr3+ emission by screening Ce3+-doped phosphor hosts for which both Ce3+ and Cr3+ can occupy the same crystallographic site. A NIR phosphor Ba3Sc4O9:Cr3+ (BSO:Cr3+) with an emission peak at 835 nm and a full width at half-maximum (FWHM) of 188 nm is obtained, where Ce3+ or Cr3+ is accommodated at the same Sc3+ site. The BSO:Cr3+ ceramic is demonstrated to produce a NIR emitter with an output power of 14.56 mW when driven by a blue laser diode at 5.0 V/100 mA. By following the proposed method, two broadband NIR phosphors composed of Li3Sc2(PO4)3:Cr3+ (λem = 1000 nm, FWHM = 223 nm) and Na3Sc2(PO4)3:Cr3+ (λem = 895 nm, FWHM = 184 nm) are further discovered.

Ambient Hydrocarbon Detection with an Ultra-Low-Loss Cavity Raman Analyzer.

The detection of ambient outdoor trace hydrocarbons was investigated with a multipass Raman analyzer. It relies on a multimode blue laser diode receiving optical feedback from a retroreflecting multipass optical cavity, effectively creating an external cavity diode laser within which spontaneous Raman scattering enhancement occurs. When implemented with ultra-low-loss mirrors, a more than 20-fold increase in signal-to-background ratio was obtained, enabling proximity detection of trace motor vehicle exhaust gases such as H2, CO, NO, CH4, C2H2, C2H4, and C2H6. In a 10-min-long measurement at double atmospheric pressure, the limits of detection obtained were near or below 100 ppb for most analytes.

Blue (0.44 µm) and red (1.7 µm) diode laser activated bleaching—dental shade changes determination

Tooth whitening or bleaching is one of the most common dental procedures that optimize the white color of the teeth and minimize the simultaneous damage to the tooth structure. Light can speed up the whitening process with halogen lamps, light-emitting diodes, plasma arc lamps, and lasers. Our results show that combinations of a teeth whitening agent with laser light irradiation with a 0.44 µm blue laser diode or a 1.7 µm near-IR laser diode accelerate the whitening process not only during tooth irradiation but also within two weeks after the procedure.

A Study on the Development of a White Light Source Module for a Large-Capacity Searchlight Using a Blue Laser Diode

In this paper, a large-capacity white light source module using a high-power blue laser diode and a reflective spaced phosphor was designed. The reflective spacing phosphor ensured thermal stability. The proposed white light module is a reflective phosphor structure with a bi-directional optical system based on a rhombus prism lens. The rhombus prism optical system can greatly narrow the blue laser beam width and a long-wavelength band-pass filter of 500 nm or more is applied to change the movement path of the laser beam and transmit white light excited by the phosphor. A dichroic filter was applied to the fold mirror part and a planar convex lens was designed to focus the blue laser beam so that the phosphor was irradiated. Finally, a high-power white light source is obtained from the pre-optics unit to which the dichroic filter is applied. In order to use the proposed white light source as a searchlight, a divergence angle of 4° or less is required. For this implementation, a large-area collimating lens combining an aspheric condensing lens and an achromatic lens was applied. It was confirmed that the divergence angle of 4 degrees or less was satisfied at the focal length (FL) of 38.5 to 42.5 mm of the optical lens of the laser white light module emitter and the collimating optical system.