Power Diode Laser Research Articles

The energy synergistic mechanism of coaxial heterogeneous-wavelength hybrid laser beam and its effect on welding molten pool dynamics for aluminum alloy

The coaxial heterogeneous-wavelength hybrid laser beam (HW-HLB) heat source featuring a “Gauss + Flat top” energy distribution, which integrates the 1080 nm and 915 nm laser beam, was employed in this paper to achieve excellent stability in the welding of aluminum alloy. The interaction mechanism between aluminum alloy and laser beams with different wavelengths was taken as a point cut to explore the synergistic enhancement mechanism of coaxial HW-HLB . A thermal-fluid coupling model for HW-HLB welding, considering the synergistic effect of dual lasers, was established according to the welding experiment results. The influence of fiber laser power (PF) and diode laser power (PD) on the molten pool flow behavior during welding process was investigated. The dynamic of the molten pool and the maintenance mechanism of the keyhole were elucidated through in-situ monitoring experiments and thermal-flow simulations. The results indicated that, in contrast to the single fiber laser beam (FLB), the power density of HW-HLB presents a significant increase, which results in the “avalanche-like” augmentation of the plasma plume, as well as deeper depth of the keyhole. The energy synergistic enhancement effect of coaxial HW-HLB with PF=2800 W and PD=2500 W performs stronger and thorough changes in the morphology and flow behavior of the molten pool. The introduction of 915 nm laser beam improves the multi-reflection behavior in the inner keyhole. The findings of our research provide a theoretical framework for improving the stability of the laser weld molten pool and the quality of welds in aluminum alloys through the implementation of HW-HLB.

Unraveling microstructure evolution induced mechanical responses in coaxial fiber-diode laser hybrid welded Fe–36Ni Invar alloy

Invar alloys, renowned for its ultra-low coefficient of thermal expansion, are qualified for widespread use in aerospace applications. This study explores the utilization of fiber-diode laser hybrid welding in Fe–36Ni Invar alloy, specifically focusing on addressing the undesirable microstructure and properties arising from unstable molten pool and high-temperature gradient encountered during single fiber laser welding. Experimental and simulation analyses were conducted to systematically explore the influence of diode laser power on the microstructure evolution and mechanical responses of fiber-diode hybrid laser welded Invar alloy joints. Results indicate that the addition of diode laser could notably widen the keyhole opening and improve the molten pool stability. An acceleration of dynamic recrystallization is observed in the weld seam, with a significant increase in high-angle grain boundaries, which account for over 90 % of the total. Moreover, with increasing diode laser power, temperature gradient decreases, leading to the formation of numerous equiaxed grains. Electron backscatter diffraction (EBSD) results demonstrate a considerable enhancement in the intensity of the γ texture, particularly the {111}<110> texture. Comparatively, fiber-diode laser hybrid welding exhibits superior plasticity and tensile strength over single fiber laser welding, with a tensile strength reaching 493.1 MPa. The research findings presented here provide essential theoretical foundations and technical guidance for enhancing the quality of Invar alloy weld joints and facilitating the broader application of fiber-diode laser hybrid welding in the future.

The Therapeutic Efficacy of Different power of Diode Laser in Surgically Apicectomized Teeth

The Therapeutic Efficacy of Different power of Diode Laser in Surgically Apicectomized Teeth

Double-Junction Cascaded GaAs-Based Broad-Area Diode Lasers with 132W Continuous Wave Output Power

Improving the output power and efficiency of broad-area diode lasers is a prerequisite for the further development of fiber lasers, solid-state laser industries, and direct semiconductor laser applications. At present, the large amount of Joule heat generated by large drive currents and limited wall-plug efficiency presents the largest challenge for improving these lasers. In this paper, a multi-junction cascade laser with low Joule heat generation is demonstrated, showing large power and conversion efficiency. We fabricated devices with different junction numbers and compared their output power. We present double-junction lasers emitting at ~915 nm with an emitter width of 500 μm, delivering 132.5 W continuous wave output power at 70 A, which is the highest power reported so far for any single-emitter laser. The power conversion efficiencies are 66.7% and 60%, at 100 W and 132 W, respectively.

Evaluation of the effect of diode laser application on the hydrophilicity, surface topography, and chemical composition of titanium dental implant surface.

Attempts have been made to decontaminate the implant surface by using diode lasers. However, the parameters that provide efficient decontamination without altering the topography or surface characteristics of titanium implants are still unclear. The aim of the present study was to evaluate the effect of altering the power of diode laser (940nm) application on the hydrophilicity, surface topography, and chemical composition of sandblasted, large grit, acid-etched (SLA) treated titanium alloy implant surface. Thirty-six SLA-treated titanium discs (Dentis Co., Ltd.) were used in this study. The hydrophilicity of all discs was measured by using a contact angle goniometer (190 CA; Rame-hart Co, Ltd). Discs were randomly divided into four groups (n = 9 each) based on the power of the diode laser used. Group I (control, no lasing group), group II: treated with 1W power, group III: 2W power, and group IV: 3W power. The chemical composition of the SLA discs was evaluated by using energy dispersive x-ray spectroscopy (EDX) before laser application. Hydrophilicity was reevaluated after the application of laser irradiation. The surface topography of all discs was examined. Changes in the chemical composition of the titanium discs were investigated following the lasing procedure. Morphometric analysis of the surface area (μm2 ) of the indentations created following laser application was also evaluated. Data were collected and the Shapiro-Wilk test of normality was used. Comparisons between the four study groups were done by using the Kruskal-Wallis test, while that to evaluate the morphometric analysis of the surface area was done by using One-way ANOVA (P<0.05). The average contact angle of the drop of distilled water to the SLA discs significantly decreased after laser treatment (P<0.05). The largest contact angle was measured in the control group, followed by the 1W group, and the 2W group. The smallest angle was measured in the 3W group. Considerable surface alterations such as melting and flattening were observed on examination of the surface topography of the 3W group followed by the 2W group. The least changes were observed in association with the 1W group in comparison to the control group. The EDX analysis showed the appearance of peaks of the oxygen and carbon elements after the lasing procedure with the highest percentage in the 3W group. The average of the surface area of the created indentations significantly increased with increasing the power of the diode laser used (P<0.05). The application of diode laser (940nm) with 2W and 3W powers significantly altered the hydrophilicity, the surface topography, and the chemical composition of titanium discs. Diode laser (940nm) with 1W power can be safely used on SLA titanium implant surfaces with no damaging effect on the surface topography or hydrophilicity.

A novel PAPR reduction scheme based on time-delay neural network for CO-OFDM systems

In this paper, we propose a low-complexity peak-to-average power ratio (PAPR) reduction scheme based on time-delay neural network (TDNN) for coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems to reduce the limitation of PAPR on the total power of laser diodes and the impact of fiber nonlinear effects. The proposed scheme is jointly trained on traditional iterative clipping and filtering (ICF) scheme and simplified clipping and filtering (SCF) scheme, and changes the objective function by adjusting the given training weight α. Compared to the original orthogonal frequency division multiplexing (OFDM) signal of existing system, our method achieves an adjustable PAPR reduction of 5.31 dB to 6.12 dB for 10−4 complementary cumulative distribution function (CCDF). When bit error rate (BER) Pe=10−3, the proposed scheme (α=0.5) achieves additional transmission distances of 220 km, 55 km, 105 km, and 100 km, compared to the original OFDM signal, partial transmission sequence (PTS) scheme, ICF scheme, and feedforward neural network (FNN)-based ICF scheme, respectively. Besides, our method achieves 86.3% and 80.0% floating-point operations (FLOPs) reductions, compared with PTS scheme and ICF scheme, respectively, which effectively reduces the complexity of PAPR reduction module, saving the system computational time.

Experimental and theoretical studies into longitudinal spatial hole burning as a power limit in high-power diode lasers at 975 nm

Spatial-hole-burning as a limit to the continuous-wave (CW) output power of GaAs-based diode lasers is experimentally studied. For 90 μm stripe lasers with 6 mm resonator length and 0.8% front facet reflectivity, spontaneous emission (SE) intensity data show that the carrier density in the device center rises rapidly at the rear facet with bias and falls at the front, consistent with simulation. At the front, the carrier density at the edge of the laser stripe also rises rapidly with bias (lateral carrier accumulation, LCA), consistent with previous observations of increased local current flow. Devices with 20% front facet reflectivity for a flat longitudinal optical field profile show smaller variation in the local carrier density. Weak variation is seen in the carrier density outside the stripe; hence, current spreading is not a power limit. SE wavelength data show higher temperatures at the front with a twofold higher increase in temperature for 0.8% than for 20% front facet. The increased front temperature likely triggers lateral spatial-hole-burning and LCA in this region, limiting power. Finally, pulsed threshold current is more strongly temperature dependent for devices with 0.8% than 20% front facets, attributed to the higher rear facet carrier density. The temperature dependence of slope in pulsed is comparable for both devices at low bias but is more rapid for 0.8% at 20 A, likely due to non-clamping at the back. The temperature dependence of slope for CW is strong with 0.8% facets, likely due to the high temperature and LCA at the front but reduced for 20% facets.

Threshold and power of pulsed red-emitting diode lasers with a bulk active layer near p-cladding under high-temperature operation

Threshold properties and pulsed output of AlGaInP visible-emitting lasers with an asymmetric waveguide structure and a bulk active layer are analysed. The effects of the current leakage, increased by the heating of the laser due to the proximity of the electrical pulse source and the Joule heating in and around this source are analysed. When optimising the laser design, waveguiding properties of the bulk active layer are shown to be important, leading to threshold currents decreasing, and injection efficiency increasing, with active layer thickness in lasers with moderately thick (< 0.1 μm) active layers.

High-power laser photobiomodulation therapy for immediate pain relief of refractory oral mucositis.

We aimed to evaluate the efficacy of high-power (class IV) laser photobiomodulation (PBM) therapy for immediate pain relief due to oral mucositis (OM) refractory to recommended first-line therapy. This retrospective study included 25 cancer patients with refractory chemotherapy- or radiotherapy-induced OM (16 and 9 patients, respectively) that were treated for pain relief with an intraoral InGaAsP diode laser (power density = 1.4 W/cm2). Pain was self-assessed immediately before and after laser treatment using a 0-to-10 numeric rating scale ([NRS], "0" = no pain, "10" = intolerable pain). Patients reported an immediate decrease in pain following 94% (74 of 79) of the PBM sessions, in 61% (48 sessions) the pain reduction was over 50%, and in 35% (28 sessions) the initial pain was completely eliminated. There were no reports of increased pain post-PBM. For chemotherapy and radiotherapy-treated patients, mean reduction in pain NRS post-PBM was 4.8 ± 2.5 (p < 0.001) and 4.5 ± 2.8 (p = 0.001), indicating a post-PBM reduction of 72% and 60% of the initial pain level, respectively. The analgesic benefit of PBM remained for a mean of 6.0 ± 5.1 days. One patient reported a transient burning sensation after one PBM session. High-power laser PBM may provide nonpharmacologic, patient-friendly, long-lasting, rapid pain relief for refractory OM.

DIAL hygrometer based on powerful laser diodes: calibration function and modulation of laser radiation

A differential absorption lidar method utilizing the spectral and energetic properties of high-power, pulsed laser diodes for remote sensing of atmospheric humidity is reported. The laser radiation of selected complementary laser diodes is multiplexed in dual spectral channels centered at optimal wavelength of 0.86µm and 0.911µm. Humidity profiles are retrieved integrating multiple resonance lines in the tunable range within the absorption spectrum of water vapor. The integral spectrum is less affected by the variable atmospheric pressure and temperature, which is an essential advantage allowing direct and reliable DIAL measurement.

Morphological substantiation of laser exposure parameters and modes for surgical treatment of intrauterine pathology

Introduction No data on experimentally substantiated parameters and modes of diode laser radiation allowing a minimally traumatic surgical treatment of intrauterine pathology have been found in the literature.The aim of the investigation was to substantiate experimentally the optimum parameters and modes of diode laser radiation in the treatment of intrauterine pathology based on the study of morphological changes in the endometrium.Materials and methods 48 endometrial samples were exposed to 10-40 W diode laser power in a constant mode and 15 samples - in a pulsed mode with 3 different sets of laser exposure parameters. The data were statistically processed using Microsoft Excel spreadsheets, version 16.49. The differences were considered statistically significant at р&lt;0.05.Results Width of the ablation zone, lateral coagulation and hyperthermic exposure zone was calculated at the most optimal parameters of laser energy (20 W), achieving adequate cutting and bleeding properties of the laser. The most effective in the pulsed mode of laser operation was 30 W amplitude power of radiation, the pulse duration of 100 ms, the duration of the interval between pulses of 50 ms, the average power of 20 W.Discussion Comparative analysis of morphometric parameters in the action of laser radiation in the constant mode with a radiation power of 20 W and in the pulsed mode with an average laser power of 20 W has shown that the structural parameters have significantly lower values in the pulsed laser mode.Conclusion Optimal cutting properties of the laser are observed when constant laser irradiation with a power of 20 W is used. The best cutting and bleeding properties were demonstrated by the pulsed laser mode with an average power of 20 W, amplitude power of 30 W, pulse duration of 100 ms, and inter-pulse interval of 50 ms.

Performance Evaluation of Input Power of Diode Laser on Machined Leather Specimen in Laser Beam Cutting Process

Numerous industries, including footwear, handicrafts, and the automobile industry, utilize leather materials. The main goal of this study was to investigate the effect of input power of the diode laser in laser cutting on vegetable chrome tanned buffalo leather to enhance the cutting process. In the present investigation, carbonization, kerf width, and material removal rate (MRR) were taken as performance measures. The diode-based laser beam machining was designed and fabricated with 2.5 W, 5.5 W, and 20 W diode laser to cut vegetable chrome tanned leather. The high-intensity 20 W diode laser produced lower carbonization, lower kerf width, and higher material removal rate compared with the 2.5 W and 5.5 W diodes. This improved performance was due to the adjustable features associated with this diode laser actuation in the form of circular shape with adjustable diameter. A high power with a lower spot size under pulsed mode can produce higher power density. Since a higher power density can establish less interaction time, it produces lower carbonization. Due to the ability of the 20 W diode laser driver to control the beam shape and size, it could produce a lower kerf width and higher MRR. The optimal parameters for cutting chrome vegetable tanned cow leather were a standoff distance of 18 mm, feed rate of 200 mm/min, and duty cycle of 70%.

Non-contact thermometer behavior of (Y0.5In0.5)2O3:Yb3+,Er3+ solid solution.

Oxides are physically and chemically stable. Non-contact thermometer-Yb3+-Er3+ ions co-doped solid solution (Y0.5In0.5)2O3, is prepared by the regular solid method. The structural results obtained by XRD indicate that a pure phase solid solution (Y0.5In0.5)2O3 has been obtained. The solid solution (Y0.5In0.5)2O3 has a similar crystal structure, especially Y2O3 and In2O3 with the same space group (Ia3̄). Green emission from 500 to 600 nm is due to Er3+ 4f-4f transitions: 4S3/2 → 4I15/2 at 567 nm and 2H11/2 → 4I15/2 at 528 nm. Red emissions from 630 to 720 nm are attributed to Er3+: 4F9/2 → 4I15/2. UC luminescence changes greatly with laser diode power and Er3+ and Yb3+ content. Furthermore, the two-photon process is confirmed to be dominant between Yb3+ and Er3+ in oxide solid solution (Y0.5In0.5)2O3. Optical temperature sensitivity is also investigated systematically in order to explore the application of the oxide solid solution (Y0.5In0.5)2O3. The temperature-dependent green fluorescence at 528 and 567 nm was investigated with the range of 313-573 K. 0.316% K-1 is the maximum absolute sensitivity at 503 K, which is higher than most Yb3+/Er3+ co-doped systems. In addition, the solid solution (Y0.5In0.5)2O3:Yb3+,Er3+ has better thermal stability and stronger UC emission than a simple substance with excellent temperature sensing performance. It indicates that Yb3+-Er3+ ions co-doped (Y0.5In0.5)2O3 solid solution is a good candidate for optical temperature sensing.

Cytotoxic effect of zinc oxide nanoparticle and diode laser combination in colorectal cancer in vitro via induction of cell cycle arrest and apoptosis

The fourth deadliest reason for cancer-related deaths worldwide was found to be colorectal cancer (CaCo2). Zinc oxide nanoparticles (ZnO-NPs) have been researched for biomedical applications due to their demonstrated anticancer, antidiabetic, antibacterial, and anti-inflammatory. by way of the cytotoxic reactive oxygen species (ROS) that are produced when photosensitizers (PSs) are activated by light, which in turn cause cancer cell death, photodynamic treatment (PDT) causes selective cytotoxicity to malignant cells. The cytotoxic effect of different concentrations and wavelengths was studied on CaCo2, and the use of combination therapy to reduce the percentage of cell lines had clear effects on early apoptosis (p-value&lt;0.05). The half-maximal inhibitory concentration (IC50) for the cell was evaluated. The proper IC50 for CaCo2 was 20 ug/ml and the target of Diode laser power is 5 5 j/cm 2. In the G2 phase of the cell cycle, a lower percentage of cells relative to the S and G1 phases was significantly different when laser and ZnO2 were combined (p-value&lt;0.05). Real-time Polyclonal chain reaction (PCR); significantly substantial variation in the use of a diode laser and ZnO2 to stop the spread of cancer by boosting the expression of the p53 gene (p-value&lt;0000). Bax a central cell death regulator, was expressed significantly (p-value&lt;0.05). Even so, utilizing the laser and ZnO2 together did not reveal any substantial differences in the Bcl2 gene (p-value&gt;0.05). In conclusion, this study supported that combination therapy was cytotoxic to CaCo2 in vitro and there is a possibility of developing it as an effective therapeutic agent.

Experimental investigation of PWM laser standoff distance control for power diode based LBM

Laser Beam Cutting (LBC) is a non-traditional excellent material processing technique preferred for robust, versatile and durable materials like leather, as it offers various benefits such as excellent accuracy and minimal tool wear due to the lack of contact between the specimen and the nozzle. In this investigation, power diode laser was preferred for leather cutting because of its longevity, monochromaticity and tunability. Pulse Width Modulation (PWM) is an input parameter that is tuned to control the output optical power of the diode laser in this study. There is no viable method availablein the field of direct adaptive control for PWM in the application of diode laser leather cutting. Hence an attempt has been proposed in this present study to control and investigate the machinability of leather by implementing the diode based LBC technology and standoff distance (SOD) control using VL6180X time of flight sensor, with indirect adaptive PWM control approach. The cutting trials were conducted on chrome tanned goat leather of thickness 0.8 mm and also this investigation reports the carbonization values and kerf width during leather cutting. It was identified that the closed loop PWM control could reduce the carbonization from 34.645 % to 30.424 % with SOD control of 20 mm. It was observed that PWM based control can enhance the machining process in an effective way.

48 W Continuous-Wave Output From a High- Efficiency Single Emitter Laser Diode at 915 nm

Improving the power and efficiency of 9xx-nm broad-area laser diodes has a great help in reducing the cost of laser systems and expanding applications. This letter presents an optimized epitaxial structure with high power and conversion efficiency. Laser diodes with 230 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> emitter width and 5 mm cavity length deliver continuous-wave output power up to 48.5 W at 48 A, 30 °C, the highest power reported for 9xx-nm single emitter lasers so far. The slope efficiency is as high as 1.23 W/A due to a low internal optical loss of 0.31 cm−1 and a high internal efficiency of 96%. The maximum power conversion efficiency reaches 72.6% at 15.3 W and 67.3% at the operating power of 30 W under a heatsink temperature of 25 °C. Life test results show no failure in 1000 hours for 55 laser diodes.

Microstructure characteristics and mechanical properties of fiber-diode hybrid laser welded 304 austenitic stainless steel

In the laser welding process using a focused Gaussian beam, high thermal gradient and molten pool instability usually lead to coarse columnar grain, poor surface quality and degradation of mechanical properties. In this paper, a beam shaping strategy that coaxially combines fiber laser and diode laser is applied in laser welding of austenitic stainless steel. Effects of the diode laser power on both the microstructures and mechanical properties are systematically studied by experiments and simulations. Results show that a fiber-diode hybrid heat source could effectively avoid unstable states of the keyhole, and has significant advantages in controlling spatter and surface morphology. Equiaxed grains tends to form on both sides of the junctions in synergistic and dominant regions due to the reduction in the thermal gradient produced by the hybrid beam. EBSD results show that the addition of diode beam weakens the formation of columnar grains along the easy slip texture <100> due to the disturbance in the liquid metal by a transverse distribution of the diode laser. Compared with the Gaussian heat source, the joint welded by the fiber-diode hybrid laser welding provides higher strength and elongation, with typical fracture morphologies of deeper and larger dimples. The optimum mechanical properties of the joint can be obtained by 2000 W fiber laser power and 1000 W diode laser power, where cracks occur in the base metal.

Watt-level beam combined diode laser systems in a chip-scale hybrid photonic platform.

Scaling up the power of on-chip diode lasers is of great importance for many emerging applications, such as integrated nonlinear optics, remote sensing, free space communication, infrared countermeasure, and light detection and ranging (LIDAR). In this manuscript, we introduce and demonstrate photonic integrated circuits (PIC) based beam combining methods to create power scalable, integrated direct diode laser systems. Traditional laser beam combining, including coherent beam combining (CBC) and wavelength beam combining (WBC), usually requires free space or fiber optical components, leading to bulky and complex systems. Instead, PIC based beam combining methods can greatly reduce the cost, size, weight, and power consumption (CSWaP) of next generation direct diode laser systems. We experimentally demonstrate four channel chip-scale CBC and WBC with watt-level on-chip power by using III/V-Si3N4 hybrid integration. Our results show that PIC based beam combining is very suitable for power scaling in a chip-scale platform.

Performance enhancement of AlGaN deep-ultraviolet laser diode using compositional Al-grading of Si-doped layers

Achieving high threshold current density and high optical confinement are big challenges in the realization of high-performance aluminum gallium nitride (AlGaN)-based deep-ultraviolet (DUV) laser diode (LD). In this work, compositional Al-grading of AlGaN layers is used to increase the optical confinement factor (OCF), carrier injection efficiency, gain, and emission power of the DUV LD. Compositional grading of waveguides (WGs) layer, electron blocking layer (EBL), and cladding layers (CLs) demonstrated that the device characteristic can be improved. By using compositional Al-grading of AlGaN p-WG, EBL, p-CL along with n-WG and n-CL, 17.4% OCF, 94.4 mW emission power, and 1369 m−1 gain at 267 nm peak emission wavelength are achieved. These improvements are attributed to the reduced threshold current density as well as using better optical confinement scheme in the DUV LD.

Intermedial annealing process applied during the growth of quantum wells and its influence on the performance of GaN-based laser diodes.

An intermedial annealing treatment is adopted during epitaxial growth of InGaN/GaN multiple quantum well (MQW) by the metal-organic chemical vapor deposition (MOCVD), which is employed after each GaN cap layer growth is finished. Optical power, threshold current and slope efficiency of GaN-based laser diodes is improved through an appropriate intermedial annealing process. A further investigation about the influence of annealing duration on the luminescence characteristics of light-emitting diodes and the surface topography evolution of single quantum well layers is conducted through the study of electroluminescence, temperature dependent photoluminescence and atomic force microscopy. It is found that the improvement of GaN-based laser diode is attributed to reduction of nonradiative recombination centers in MQW, which is due to a better interface quality between well and barrier layers after an intermedial annealing process.