Red Diode Laser Research Articles

Multiemitter 638-nm high-power broad area laser diodes for display application

Laser-based displays have gathered much attention because only the displays can express full color gamut of Ultra-HDTV, ITU-R BT.2020. There are many types of laser-based displays. A projector with a single spatial light modulator is mainstream in the displays so far. This projector uses the laser light sources under pulse with duty of 20% to 50%. We improve a triple-emitter red color 638-nm high-power broad area laser diode (LD) for this application. Countermeasures are adopted to improve the output power characteristics and strengthen the facet to the fatal degradation. The improved triple emitter shows the output of 5.0 W at the injection current of 5 A under pulse with duty of 30%, case temperature of 25°C. The output is increased by 4.1% compared to our former one. The peak wall plug efficiency reaches to 41.6% under 25°C. The long-term aging test is also performed. Mean time to failure of the improved LD is estimated 72,000 h under the output of 3.5 W, pulse condition with duty of 30%. The value is ∼3.3 times longer than that of the former.

Tricolor visible-light laser diodes based visible light communication operated at 40.665 Gbit/s and 2 m free-space transmission.

Visible light communication (VLC) can provide a dedicated, secure, and high data rate wireless transmission link. It has gained considerable attentions recently, and is considered as one of the promising technologies for beyond 5G mobile and wireless communications. In this work, we demonstrate a VLC system with a recorded data rate of 40.665 Gbit/s using tricolor red, green and blue (RGB) laser diodes (LDs) and polarization multiplexing. 2 m free-space transmission distance is achieved. The implementation of bit-loading, power-loading, and polarization multiplexing are discussed. Experimental bit-error-ratio (BER) results show that each of the 6 polarization and wavelength de-multiplexed channels can achieve the forward-error-correction (FEC) requirement.

POTENTIAL OF 77,78 mW RED DIODE LASER FOR PHOTODYNAMIC

A laser is a light source that uses for any kinds of medical application. Diode Laser is one laser type using in the medical application such as Photodynamic Therapy and Photodynamic inactivation. Photodynamic Therapy is one of non-invasive therapy using for many therapies such as antimicrobial therapy, rejuvenating skin therapy, anti-aging skin therapy, etc. This therapy is using a light source with specific characteristics of wavelength in some case are using Light-sensitive molecules. This research aims to determine the potential of the diode laser for photodynamic therapy instrument. Diode Laser with wavelength value 660nm is Red Laser Diode that has main power output 79,4 mW. The application was using 1 cm clearance with the 30s of time exposure. The result showed that for Diode Laser (λ) 660nm using 7,8x10 -2 W input power produce 77,78 mW output power; has operational temperature 53.56 o C and light beam 4.2 mm 2 . DOI : https://doi.org/10.26905/jeemecs.v2i2.3254

Clinical evaluation of a fluoride gel, a low-level laser, and a resin varnish at the treatment of dentin hypersensitivity

This clinical trial aims to evaluate in vivo the efficacy of a fluoride gel, a low-level laser (LLL), and a resin varnish at the treatment of dentin hypersensitivity (DH). Treatments assessed for their effectiveness, immediate analgesia, and duration of desensitization. A total of 78 patients (one tooth per patient) with a clinical diagnosis of dentin hypersensitivity were included in this clinical trial. Dentin sensitivity in response to an air blast stimulus was assessed, and a Numeric Rating Scale (NRS) for pain from 0 to 10 was chosen to quantify pain at baseline and 15 min, 1 month, and 3 months after the first application. Patients were randomly divided into three groups. In the first group (treatment A, 26 patients), a fluoride gel (Calmodent Professional, Intermed, Greece) was applied. In the second group (treatment B, 26 patients), teeth were irradiated by a 670-nm InGaAlP continuous wave, red diode laser (MED-701, Lasotronic, Switzerland) with an output power of 180 mW, energy of 5.4 J, and irradiation time of 30 s. In the third group (treatment C, 26 patients), a resin varnish with giomer technology (PRG Barrier Coat, Shofu, Japan) was applied. The main analysis of the results was done with a linear mixed model (algorithm MIXED, IBM Statistics SPSS 21.0), while pairwise comparisons were conducted with the Bonferroni method. The statistical significance for all tests was set at p < 0.05. The main effects of time and group were found to be statistically significant. The time × group interaction effect was also statistically significant, and finally, a significant reduction (p < 0.05) of DH was recorded in all groups, compared with baseline. All three treatments offered satisfactory and prolonged results.

Analysis of optical injection on red and blue laser diodes for high bit-rate visible light communication

In this work, self-injection and external-injection in ∼450 nm InGaN/GaN blue and ∼650 nm InGaP/AlGaInP red diode lasers are investigated. A distinct locking characteristic is observed in the self-injection case with small 19 cm cavity length, demonstrating enhanced ∼2.34 and ∼2.07 GHz 3-dB bandwidths, corresponding to a factor of ∼1.4 and ∼1.1 improvement, and reduced ∼60 and ∼80 pm spectral linewidths, for the blue and the red lasers, respectively. Moreover, this short external cavity self-injection locked system exhibited superior performance by a factor of 1.1–1.3 compared to the long cavity (26 cm) configuration. Conversely, the external optical injection exhibited weak locking signature with improved linewidths by a factor of ∼1.6–2.8 and reaching as small as ∼70 and ∼87 pm for the blue laser, respectively, while almost doubling in the peak powers. Later, on–off keying modulation technique based data transmission rates of up to 3.5 and 4.5 Gb/s are demonstrated on free-running blue and red laser diodes, respectively, employing an in-house laser diode mount based system. Moreover, owing to the bandwidth limitation of the optically injected systems, successful transmission of up to 2 Gb/s is demonstrated with better performance compared to the respective free-running cases, in particular, the external-optically injected system demonstrated more than double improvement in the bit-error-rate.

Diode laser photoacoustic spectroscopy of CO2, H2S and O2 in a differential Helmholtz resonator for trace gas analysis in the biosciences and petrochemistry

Photoacoustic spectroscopy in a differential Helmholtz resonator has been employed with near-IR and red diode lasers for the detection of CO2, H2S and O2 in 1 bar of air/N2 and natural gas, in static and flow cell measurements. With the red distributed feedback (DFB) diode laser, O2 can be detected at 764.3 nm with a noise equivalent detection limit of 0.60 mbar (600 ppmv) in 1 bar of air (35-mW laser, 1-s integration), corresponding to a normalised absorption coefficient α = 2.2 × 10−8 cm−1 W s1/2. Within the tuning range of the near-IR DFB diode laser (6357–6378 cm−1), CO2 and H2S absorption features can be accessed, with a noise equivalent detection limit of 0.160 mbar (160 ppmv) CO2 in 1 bar N2 (30-mW laser, 1-s integration), corresponding to a normalised absorption coefficient α = 8.3 × 10−9 cm−1 W s1/2. Due to stronger absorptions, the noise equivalent detection limit of H2S in 1 bar N2 is 0.022 mbar (22 ppmv) at 1-s integration time. Similar detection limits apply to trace impurities in 1 bar natural gas. Detection limits scale linearly with laser power and with the square root of integration time. At 16-s total measurement time to obtain a spectrum, a noise equivalent detection limit of 40 ppmv CO2 is obtained after a spectral line fitting procedure, for example. Possible interferences due to weak water and methane absorptions have been discussed and shown to be either negligible or easy to correct. The setup has been used for simultaneous in situ monitoring of O2, CO2 and H2S in the cysteine metabolism of microbes (E. coli), and for the analysis of CO2 and H2S impurities in natural gas. Due to the inherent signal amplification and noise cancellation, photoacoustic spectroscopy in a differential Helmholtz resonator has a great potential for trace gas analysis, with possible applications including safety monitoring of toxic gases and applications in the biosciences and for natural gas analysis in petrochemistry.Graphical abstract

Antimicrobial Photodynamic Therapy Protocols on Streptococcus mutans with Different Combinations of Wavelengths and Photosensitizing Dyes.

The aim of the study is to test the application of different laser wavelengths, with and without different photosensitizing dyes on different types of cultures. Laser irradiation was realized on Streptococcus mutans in both solid and liquid culture media in continuous mode at three different fluences (10, 20, and 30 J/cm2) with a red diode (650 nm) with toluidine blue dye, a blue-violet diode (405 nm) with curcumin dye, and a green diode (532 nm) with erythrosine dye. Without a photosensitizer, no growth inhibition was obtained with the red diode at any fluence value. Inhibition rates of 40.7% and 40.2% were obtained with the blue diode and green diode. The blue diode laser used with curcumin obtained results in terms of growth inhibition up to 99.26% at a fluence of 30 J/cm2. The red diode laser used with toluidine blue obtained results in terms of growth inhibition up to 100% at fluences of 20 and 30 J/cm2. The KTP (potassium-titanyl-phosphate) laser used with erythrosine was able to determine a complete growth inhibition (100%) at the different fluence values. The combination of a laser and its proper color may dramatically change the results in terms of bactericidal effect. It will be interesting to confirm these data by further in vivo studies.

Optimization of Bending Angle of Fiber Optic Sensor for Non-Invasive Blood Glucose Measurement

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Optical Fiber Polymer Sensor System with TiO2-SiO2 Cladding for Measuring Humidity

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Li5 Zn8 Ga5 Ge9 O36 : Cr3+ , Ti4+ : A Long Persistent Phosphor Excited in a Wide Spectral Region from UV to Red Light for Reproducible Imaging through Biological Tissue.

Near-infrared (NIR) long-persistent phosphors (LPPs) have emerged as a potential solution for bio-imaging applications over the past few years. However, there are enormous challenges regarding their in situ application based on their dependence on short-wavelength excitation. In this paper, we report a multi-spectral excited NIR LPP, Li5 Zn8 Ga5 Ge9 O36 : 1.5 % Cr3+ , 0.5 % Ti4+ , which overcomes the limitations of functional processes in biological tissues and other complex systems. This LPP exhibits a high luminescent intensity and a long emission duration in the NIR region (700-800 nm). The applicability of this phosphor to tissue imaging is demonstrated experimentally. Its persistent luminescence (PersL) can easily penetrate approximately 2 mm of pork flesh. More importantly, this phosphor can be re-charged in situ using a red LED or laser diode array to provide renewed NIR PersL for biological tissues, which is beneficial for long-term biological tissue imaging applications with high signal-to-noise ratios. Systematic investigations of the nature of energy traps and PersL mechanisms are also reported in this paper.

Regularly arranged Eu-doped GaN nanocolumns grown by RF-plasma-assisted molecular beam epitaxy through Ti-mask selective-area growth technique

Eu-doped GaN (GaN:Eu) is a good candidate for realizing red laser diodes with temperature stability. Nanocolumn crystals are useful for achieving a high optical gain by a high Eu concentration because they can suppress the degradation of crystalline quality. In this study, regularly arranged GaN:Eu or InGaN:Eu/GaN quantum well (QW) nanocolumns were fabricated using the Ti-mask selective-area growth technique by RF-plasma-assisted molecular beam epitaxy. A sharp luminescence corresponding to inner shell electron transition was observed at approximately 620 nm for both the samples. The regular arrangement resulted in a high extinction ratio and uniform emission distribution. Many undesirable nanocrystals observed on the Ti mask due to low-temperature growth of GaN:Eu were easily removed by preparing a SiO2 layer under the Ti mask and lifting it using a HF treatment. The main peaks and emission efficiency of the InGaN:Eu QW nanocolumns depended on the column diameter, with thick nanocolumns (diameters of more than 260 nm) showing a high emission efficiency. These results suggested that regularly arranged GaN:Eu nanocolumns can be one of the basic technologies for the realization of novel optical devices.

Antimicrobial photodynamic activity of toluidine blue encapsulated in mesoporous silica nanoparticles against Pseudomonas aeruginosa and Staphylococcus aureus

In the present study, the antimicrobial and antibiofilm efficacy of toluidine blue (TB) encapsulated in mesoporous silica nanoparticles (MSN) was investigated against Pseudomonas aeruginosa and Staphylococcus aureus treated with antimicrobial photodynamic therapy (aPDT) using a red diode laser 670 nm wavelength, 97.65 J cm−2 radiant exposure, 5 min). Physico-chemical techniques (UV-visible (UV-vis) absorption, photoluminescence emission, excitation, and FTIR) and high-resolution transmission electron microscopy (HR-TEM) were employed to characterize the conjugate of TB encapsulated in MSN (TB MSN). TB MSN showed maximum antimicrobial activities corresponding to 5.03 and 5.56 log CFU ml−1 reductions against P. aeruginosa and S. aureus, respectively, whereas samples treated with TB alone showed 2.36 and 2.66 log CFU ml−1 reductions. Anti-biofilm studies confirmed that TB MSN effectively inhibits biofilm formation and production of extracellular polymeric substances by P. aeruginosa and S. aureus.

Efficiency of methylene blue-mediated photodynamic therapy vs intense pulsed light in the treatment of onychomycosis in the toenails.

Photodynamic therapy (PDT) or intense pulsed light (IPL) are efficient therapeutic methods in the treatment of superficial skin infections, and thus, they could be good options for onychomycosis treatment, the most common nail disorder. Forty patients, affected with different diagnosed types of onychomycosis in nails of the first toe, were randomly divided into two groups of 20 patients to be treated by PDT or IPL. Nail plates were softened with urea 40% by occlusive dressing for 12hours during 3-7days before treatments. Then, eight sessions separated by an interval of 2weeks of a PDT protocol mediated by methylene blue (MB) and red laser diode (Periowave® , λ=670nm, 200mW) or an IPL protocol based on 10pulses/cm2 (Dye-VL-F module, Alma Lasers, λ=500-600nm, 10J) were applied. Both treatments reduced significantly the Onychomycosis Severity Index (OSI) (P<0.05). In terms of complete cure: 70% (PDT) and 80% (IPL) of the patients reached it after 12weeks post-treatment. No patient reported any adverse effects or complications, although in the IPL Group, some referred pain sensation during light irradiation and hematomas apparition. Photodynamic therapy and IPL were effective for onychomycosis cure of any etiology.

Al-free cladding-layer blue laser diodes with a low aspect ratio in far-field beam pattern * * Project supported by the National Key R&D Program (Nos. 2017YFB0403100, 2017YFB0403101), the National Natural Science Foundation of China (Nos. 61534007, 61404156, 61522407, 61604168, 61775230), the Key Frontier Scientific Research Program of the Chinese Academy of Sciences (No. QYZDB-SSW-JSC014), the Science and Technology Service Network

c-plane GaN-based blue laser diodes (LDs) were fabricated with Al-free cladding layers (CLs) and deepened etching depth of mesa structure, so the aspect ratio of the far-field pattern (FFP) of the laser beam can be reduced to as low as 1.7, which is nearly the same as conventional AlGaInP-based red LDs. By using GaN CLs, the radiation angle of the laser beam θ⊥ is only 10.1° in the direction perpendicular to the junction plane. After forming a deeply etched mesa, the beam divergence angle parallel to the junction plane of FFP, θ//, increases from 4.9° to 5.8°. After using the modified structure, the operation voltage of LD is effectively reduced by 2 V at an injection current of 50 mA, but the threshold current value increases. The etching damage may be one of the main reasons responsible for the increase of the threshold current.

Alteration of Surface Glycoproteins After Photodynamic Therapy

Cell membranes have been identified as an important intracellular cancer treatment target, since the glycoconjugates present on the cell surface are involved in numerous cell functions. Photodynamic therapy (PDT) is a therapeutic modality employed in the treatment of tumors that uses visible light to activate a photosensitizer. This study analyzed the expression of surface carbohydrates after PDT with two different photosensitizers, 5-aminolevulinic acid (ALA) and Photosan-3. Mice were injected subcutaneously with 2 × 105 B16 cells. After 7-10 days, the presence of a tumor with a diameter of 3.6 mm was observed. Photosan-3® and 5-aminolevulinic acid-ALA were used in the PDT treatment. Control animals (not submitted to either laser treatment or photosensitizer injection) and treated animals were euthanized 15 days post-treatment. The tumors were irradiated with a red diode laser, λ = 655 nm, energy density of 10 J.cm-2, and power density of 45 mW.cm-2. After 2 weeks of treatment with PDT, the mice were euthanized, the tumors were collected, and the cell surfaces were labeled with lectins concanavalin A (ConA) and wheat germ agglutinin (WGA). Fluorescence microscopy analysis of the cell surfaces with lectins ConA and WGA showed the presence of α-mannose and α-glucose. The combined effects of either Photosan-3 or ALA and red laser light on melanoma suggest an inhibitory glycosylation action from PDT on the surface of B16-F10 cells.

Laser-based white-light source for high-speed underwater wireless optical communication and high-efficiency underwater solid-state lighting.

White light generated by mixing the red, green, and blue laser diodes (RGB LDs) for simultaneous high-speed underwater wireless optical communication (UWOC) and high-efficiency underwater solid-state lighting (SSL) was proposed and demonstrated experimentally for the first time. The allowable maximum real-time data transmission rates of 3.2 Gbps, 3.4 Gbps, and 3.1 Gbps for RGB LDs with corresponding BERs of 3.6 × 10-3, 3.5 × 10-3 and 3.7 × 10-3 were obtained at a 2.3 m underwater transmission distance using an on-off keying (OOK) modulation scheme, respectively. And the corresponding UWOC aggregate data rate of 9.7 Gbps was achieved based on RGB LDs-based wavelength-division multiplexing (WDM) UWOC. Moreover, UWOC and underwater SSL by using RGB LDs mixed white light were investigated at different scenarios over an underwater link of 2.3 m. The RGB LDs mixed white light-based UWOC system without optical diffusers yielded a maximum allowable data rate of 8.7 Gbps with Commission International de l'Eclairage coordinates (CIE) of (0.3154, 0.3354), a correlated color temperature of 6322 K, a color rendering index of 69.3 and a corresponding illuminance of 7084 lux. Furthermore, optical diffusers were employed to provide large-area underwater SSL. The LDs mixed white light-based UWOC system with line and circle optical diffusers implemented data rates of 5.9 Gbps and 6.6 Gbps with CIE coordinates of (0.3183, 0.3269) and (0.3298, 0.3390), respectively. This work suggests the potential of LDs for applications in high-efficiency underwater white-light SSL and high-speed UWOC.

Red (635 nm), Near-Infrared (808 nm) and Violet-Blue (405 nm) Photobiomodulation Potentiality on Human Osteoblasts and Mesenchymal Stromal Cells: A Morphological and Molecular In Vitro Study.

Photobiomodulation (PBM) has been used for bone regenerative purposes in different fields of medicine and dentistry, but contradictory results demand a skeptical look for its potential benefits. This in vitro study compared PBM potentiality by red (635 ± 5 nm) or near-infrared (NIR, 808 ± 10 nm) diode lasers and violet-blue (405 ± 5 nm) light-emitting diode operating in a continuous wave with a 0.4 J/cm2 energy density, on human osteoblast and mesenchymal stromal cell (hMSC) viability, proliferation, adhesion and osteogenic differentiation. PBM treatments did not alter viability (PI/Syto16 and MTS assays). Confocal immunofluorescence and RT-PCR analyses indicated that red PBM (i) on both cell types increased vinculin-rich clusters, osteogenic markers expression (Runx-2, alkaline phosphatase, osteopontin) and mineralized bone-like nodule structure deposition and (ii) on hMSCs induced stress fiber formation and upregulated the expression of proliferation marker Ki67. Interestingly, osteoblast responses to red light were mediated by Akt signaling activation, which seems to positively modulate reactive oxygen species levels. Violet-blue light-irradiated cells behaved essentially as untreated ones and NIR irradiated ones displayed modifications of cytoskeleton assembly, Runx-2 expression and mineralization pattern. Although within the limitations of an in vitro experimentation, this study may suggest PBM with 635 nm laser as potential effective option for promoting/improving bone regeneration.

Highly Uniform White Light-Based Visible Light Communication Using Red, Green, and Blue Laser Diodes

With the development of wireless optical communication and solid-state lighting, the high efficiency, large bandwidth, and high uniform white light source becomes more and more important. In this paper, a white light source generated by red, green, and blue laser diodes (RGB LDs) was synthetized according to the calculated power ratio of RGB LDs based on the chromaticity theory. The high coherence of the lasers normally leads to the nonuniform white light. Thus, it is to improve the illumination quality of the lighting source by employing micro lens for the purpose of homogenization. The simulation results showed that the uniformity of the white light incoherent radiation was above 90% which proves that the coherence of the lasers was destroyed. In addition, the photoelectric parameters of the RGB-LD mixed white light after homogenization was characterized. Meanwhile, the modulation bandwidth of RGB LDs before and after homogenization was analyzed, respectively, and it shows that the bandwidth was more than 1 GHz, which is limited by the photodetector cut-off frequency. Such a high-uniformity and high-speed RGB-LD mixed white light can be deployed for illumination and wireless communication simultaneously.

CD31 expression in human primary teeth treated with photobiomodulation therapy

This study aimed to evaluate the effects of photobiomodulation (PBM) on CD31 expression in pulp tissue repair of human primary teeth. Fifteen mandibular primary molars were divided into the following groups: GI—calcium hydroxide (CH), GII—PBM + CH, and GIII—PBM + zinc oxide/eugenol (ZOE). In the GII and GII groups, an indium–gallium–aluminum phosphide (InGaAlP) diode laser was used for the irradiation through 320-μm diameter optical fiber in contact with pulp tissue. The red laser diode parameters were set at 660-nm wavelength, 10-mW power output, 2.5-J/cm2 energy density, 50–60-Hz frequency, output beam area of 0.04 cm2, and irradiation time of 10 s in continuous mode. After pulpotomy treatment, clinical and radiographic follow-ups were accomplished until the teeth achieved regular exfoliation period. Teeth were extracted for histological analysis and immunolocalization of CD31. Histopathological statistical analyses were performed by Kruskal-Wallis followed by Dunn test to determine statistically significant differences (p < 0.05). Although GII showed no inflammation or discreet inflammatory cells, the comparison among the groups using a score system revealed no statistically significant differences regarding inflammation and the amount of blood vessels. The immunohistochemistry analysis revealed positive CD31 expression in the blood vessels of all the studied groups. Immunostaining was observed in large blood vessels associated with inflammatory cells on GI and GIII, whereas GII showed discreet immunostaining predominantly in small blood vessels scattered throughout the pulp tissue with none or rare inflammatory cells. The CD31 expression was greater in the group PBM when associated with calcium hydroxide. Photobiomodulation therapy followed by calcium hydroxide helped in repairing and seemed to regulate angiogenesis and leukocyte migration processes in the remaining pulp tissue after primary teeth pulpotomy.

Low-power laser irradiation decreases lipid droplet accumulation in the parotid glands of diabetic rats.

Lipid droplet accumulation has been related to salivary gland hypofunction in diabetes. In this study, the effect of laser irradiation on the parotid glands (PGs) of diabetic rats was analyzed with regard to its effect on lipid droplet accumulation, intracellular calcium concentration and calmodulin expression. The animals were distributed into 6 groups: D0, D5, D20 and C0, C5, C20, for diabetic (D) and control animals (C), respectively. Twenty-nine days following diabetes induction, PGs of groups D5 and C5; D20 and C20 were irradiated with 5 and 20 J/cm2 of a red diode laser at 100 mW, respectively. After 24 hours, PGs were removed for histological, biochemical, and western blotting analysis. The diabetic animals showed lipid droplet accumulation, which was decreased after irradiation. Ultrastructurally, the droplets were nonmembrane bound and appeared irregularly located in the cytoplasm. Moreover, diabetic animals showed an increased intracellular calcium concentration. In contrast, after laser irradiation a progressive decrease in the concentration of this ion was observed, which would be in agreement with the results found in the increased expression of calmodulin in D20. These data are promising for using laser to decrease lipid droplet accumulation in PGs, however, more studies are necessary to better understand its mechanisms. Micrographs showing decreased lipid accumulation after laser irradiation in light micrographs (LM), and morphology of lipid droplet in transmission electron microscopic (TEM). LM: (A) PGs from nondiabetic rats that did not receive Laser irradiation (LI), (B) PGs from nondiabetic rats that received a dose of 20 J/cm2 , (C) lipid accumulation (arrows) in the secretory cells from diabetic rats that did not receive irradiation, (D) reduction of lipid accumulation in the secretory cells from diabetic rats that received a dose of 20 J/cm2 and TEM: (E) scale bar = 5 μm, (F) scale bar = 1 μm, and (G) scale bar = 0.5 μm.