High-power Diode Research Articles

High-efficiency edge-emitting laser diodes with oxidation confinement stripe structure

High-efficiency, low-cost, high-power laser diodes (LDs) are in the spotlight due to the growing market demand. This study proposes a new edge-emitting LD structure that utilizes the facile oxidization properties of the high aluminum (Al) component AlGaAs material and simplifies LD fabrication to only one-step lithography. The key innovation is incorporating a ∼200 nm thick high-Al AlGaAs layer in the vertical epitaxial structure. This layer serves two purposes: 1) The low refractive index improves vertical mode confinement, enabling a thinner overall epitaxial structure. 2) Oxidation of this layer forms a dielectric isolator and a current aperture. Experimental LDs exhibited a peak efficiency of 77.8 %, peak power of 33.6 W, vertical divergence angle of 19.4°, and horizontal divergence angle of 8.8°. Compared to conventional edge-emitting LD, this LD demonstrates a 39 % lower thermal resistance, better optoelectronic performance, a simpler process, and a lower production cost.

Interface Contact Thermal Resistance of Die Attach in High-Power Laser Diode Packages

The reliability of packaged laser diodes is heavily dependent on the quality of the die attach. Even a small void or delamination may result in a sudden increase in junction temperature, eventually leading to failure of the operation. The contact thermal resistance at the interface between the die attach and the heat sink plays a critical role in thermal management of high-power laser diode packages. This paper focuses on the investigation of interface contact thermal resistance of the die attach using thermal transient analysis. The structure function of the heat flow path in the T3ster thermal resistance testing experiment is utilized. By analyzing the structure function of the transient thermal characteristics, it was determined that interface thermal resistance between the chip and solder was 0.38 K/W, while the resistance between solder and heat sink was 0.36 K/W. The simulation and measurement results showed excellent agreement, indicating that it is possible to accurately predict the interface contact area of the die attach in the F-mount packaged single emitter laser diode. Additionally, the proportion of interface contact thermal resistance in the total package thermal resistance can be used to evaluate the quality of the die attach.

PT Symmetry and Radiation Structure of High-Power Laser Diodes

PT Symmetry and Radiation Structure of High-Power Laser Diodes

Development of a blue-violet high-power single-frequency diode laser system for 48Ca isotope separation

Development of a blue-violet high-power single-frequency diode laser system for ⁴⁸Ca isotope separation

Fine and Rough Structures of the Frequency Spectrum of a High-Power Laser Diodes during Slow Degradation

Fine and Rough Structures of the Frequency Spectrum of a High-Power Laser Diodes during Slow Degradation

Precise mode control of mid-infrared high-power laser diodes using on-chip advanced sawtooth waveguide designs

Abstract Power scaling in conventional broad-area (BA) lasers often leads to the operation of higher-order lateral modes, resulting in a multiple-lobe far-field profile with large divergence. Here, we report an advanced sawtooth waveguide (ASW) structure integrated onto a wide ridge waveguide. It strategically enhances the loss difference between higher-order modes and the fundamental mode, thereby facilitating high-power narrow-beam emission. Both optical simulations and experimental results illustrate the significant increase in additional scattering loss of the higher-order modes. The optimized ASW lasers achieve an impressive output power of 1.1 W at 4.6 A at room temperature, accompanied by a minimal full width at half maximum lateral divergence angle of 4.91°. Notably, the far-field divergence is reduced from 19.61° to 11.39° at the saturation current, showcasing a remarkable 42% improvement compared to conventional BA lasers. Moreover, the current dependence of divergence has been effectively improved by 38%, further confirming the consistent and effective lateral mode control capability offered by our design.

Highly sensitive detection of oxygen based on light-induced thermoelastic spectroscopy with a high power diode laser

Oxygen (O2) is a fundamental element in the atmosphere. It is important to detect it in various fields. In this paper, a sensitive O2 sensor based on light-induced thermoelastic spectroscopy (LITES) with a high power diode laser is reported. A distributed feedback (DFB) diode laser emitting at 760 nm with output power of 16.8 mW was employed as the light source. The O2 absorption line at 13144.54 cm-1 was selected for the investigation. Wavelength modulation spectroscopy (WMS) technique and second harmonic signal demodulation (2f) were adopted to improve the sensing performance. For the concentration dynamic range from 20% to 80%, a linear relationship between the amplitude of 2f signal and O2 concentration was demonstrated. Allan deviation analysis was conducted to evaluate the long-term stability of the sensor system and the minimum detection limit (MDL) was measured to be 583 ppm at the optimum integration time of 100 s. Further improvement of this O2-LITES sensor system was also discussed.

Сучасні аспекти клініки, діагностики та лікування ВПЛ-асоційованих доброякісних уражень ротової порожнини

Human papillomavirus (HPV) exhibits specific tropism for squamous epithelium and therefore contributes to the development of many benign, potentially malignant, and malignant epithelial lesions. The benign HPV-related lesions of the oral cavity comprise verruca vulgaris, squamous papilloma, condyloma acuminatum and multifocal epithelial hyperplasia. Oral squamous papilloma is most common in people of various ages. Purpose: To determine the structure, clinical features and morphological signs of oral squamous papilloma in patients of different sex and age. Materials and methods. For the period of 2020-2023, 18 people with oral papilloma (papillomatosis) aged 15 to 70 years were examined. In 12 patients, papilloma was removed by conventional surgery, in 6 patients – using a high power diode laser. Pathohistological evaluation of excisional biopsy and identification/genotyping of HPV DNA by REAL TIME PCR was carried out. Results. Squamous papilloma dominates in the structure of HPV-related benign oral lesions (88.8%). Among patients with papiloma, the majority are women (72.2%) with an average age of 29.3±4.0 years. The average age of men with papilloma is 52.2±5.8 years. By localization in the oral cavity, papillomas are most often found on the gingiva (43.75%), as well as on the tongue (25%), on the soft palate (18.75%), on the mucous membrane of the upper lip (6.25%) and cheek (6.25%). The average papilloma size by diameter was 0.71±0.06 cm. Pathomorphological confirmation of the impact of HPV on the development of oral squamous papilloma, namely the presence of coylocytes, was obtained in 31.3% of excision biopsies. Hyperkeratosis of the covering epithelium was found in 5 patients (27.7%), and this condition is defined as «keratopapiloma». In 6 women (33.3%), the presence of various types of HPV was detected by PCR, including high oncogenic risk (HPV-16, 18, 66, 68). Conclusion. Oral squamous papilloma, associated with high oncogenic risk HPV, as well as keratopapilloma in heavy smokers, should be considered a precancerous disease of the oral mucosa with a high risk of malignancy. Key words: human papillomavirus, papillomavirus infection, oral squamous papilloma, keratopapiloma, laboratory diagnostics, oral mucosa, risk of malignancy

Eficácia do laser de diodo de alta potência como coadjuvante à instrumentação mecânica de bolsa profunda em paciente com periodontite estádio III, grau C e generalizada

ABSTRACT Periodontitis is an inflammatory clinical condition caused by dysbiotic biofilm that results in progressive destruction of periodontal attachment and can lead to tooth loss if left untreated. Objective: To evaluate the clinical efficacy of high-power diode laser as an adjunct to mechanical instrumentation in periodontal pockets of a patient with generalized, stage III, grade C periodontitis. Methods: 126 sites of a patient were examined at the Clinical Research Laboratory (LabClin) of the Federal University of Campina Grande (UFCG), where the parameters of probing depth (PD), clinical attachment level (CAL) and bleeding on probing (BoP) were evaluated at the beginning of the study and after 3 and 6 months of basic therapy. All sites received non-surgical periodontal treatment which corresponds to scaling and root planing (SRP) and coronary polishing. The deep periodontal pockets with PD ≥ 5 mm, received the adjuvant therapy with diode laser light. Results: There was a significant improvement of periodontal parameters of PD, CAL and BoP in all treated sites. In those with PD ≥ 5 mm, the results were similar, with statistically significant reduction of PD, CAL and BoP before and after treatment. After 6 months, all periodontal pockets with PD ≥ 5mm were reduced to values lower than 3. Conclusion: The irradiation of deep pockets with high-power diode laser proved to be effective as adjuvant therapy to SRP in patients with generalized, stage III, degree C periodontitis.

Continuous Flow Synthesis of Nitrosoarenes via Photochemical Rearrangement of Aryl Imines.

Nitrosoarenes are versatile organic building blocks; however, their intrinsic instability and limited synthetic accessibility have so far restricted their widespread use. Herein, we present a new continuous flow route toward these entities that is based on a direct photochemical rearrangement process using o-nitrophenylimines as starting materials. Due to the underlying redox mechanism, a new amide group accompanies the formation of the nitroso group. Crucial to the success of this approach is the use of trifluoroethanol as a solvent and high-power light-emitting diodes (365 nm) as light sources that provide uniform irradiation and high efficiency of the resulting continuous flow method. The process is fast and robust, with high functional group tolerance and high throughput. The formation of the nitroso moiety is supported by full spectroscopic analysis, including X-ray crystallography. The scalability of this flow approach allows access to gram quantities of nitroso species for which we highlight a small set of derivatization reactions underlining their synthetic utility.

Trace gas sensor based on a multi-pass-retro-reflection-enhanced differential Helmholtz photoacoustic cell and a power amplified diode laser.

A high-sensitive photoacoustic spectroscopy (PAS) sensor, which is based on a multi-pass-retro-reflection-enhanced differential Helmholtz photoacoustic cell (DHPAC) and a high power diode laser amplified by erbium-doped fiber amplifier (EDFA), is presented in this work for the first time. In order to improve the interaction length between the light and target gas, the incident light was reflected four times through a multi-pass-retro-reflection-cell constructed by two right-angle prisms. A 1.53 µm distributed feedback (DFB) diode laser was selected to excite photoacoustic signal. Moreover, its power was amplified by an EDFA to 1000 mW to improve the amplitude of photoacoustic signal. Acetylene (C2H2) was chosen as the target analysis to verify the reported sensor performance. Compared to double channel without multiple reflections, the 2f signal of double channel with four reflections was improved by 3.71 times. In addition, when the output optical power of EDFA was 1000 mW, the 2f signal has a 70.57-fold improvement compared with the multi-pass-retro-reflection-cell without EDFA. An Allan deviation analysis was carried out to evaluate the long-term stability of such PAS sensor. When the averaging time was 400 s, the minimum detection limit (MDL) of such PAS sensor was 14 ppb.

Development of an all-solid-state air-cooled high-power blue diode laser for metal processing.

We present the design and development of an all-solid-state (fluid/refrigerant-free) 100 W scale blue-laser system and show its applications in precision copper works. We combine powerful laser-diode arrays with Peltier chips on a compact laser head to achieve stable thermal and optical performance. Good agreement between the thermal simulation of the 3D laser head and experiments validates stable thermal performance. The laser system emits 40-100W continuous wave at λ = 452.2 ± 2.5 nm with 98% power stability and ∼24% wall-plug efficiency inside a portable enclosure. This is the first, to the best of our knowledge, all-solid-state air-cooled laser with a 100 W class output. We achieved kW/cm2 intensity level on an mm-size focus with this source and demonstrated cutting, bending, and soldering copper on a battery pack. Furthermore, the copper-solder joints have nanoscale adhesion without cracks. Additionally, we unveil that 0.5-4 kW/cm2 intensity laser annealing scan makes copper strips mechanically resilient to withstand extreme loading cycles without nanoscale cracks.

High-power fiber-coupled diode laser welding of 10-mm thick Inconel 617 superalloy

In the present study, a high beam quality fiber-coupled diode laser was effectively utilized to weld 10-mm thick Inconel 617 superalloy in single pass. Influence of critical parameters of focusing distance and welding speed on weld characteristics was systematically investigated and optimized. At optimum process conditions with the power density of ≈106 W/cm2, crack-free full-penetration weld with minimal distortion, porosity, and no underfill/undercut/root-hump defects were obtained with 97%–99% joint efficiency. The weld joint quality produced was on par with multipass employing conventional lasers and advanced laser-hybrid welding techniques and sufficient enough to apply in various applications of thermal power plants, ship building, and heavy industries.

Improved Far-Field Angle in Narrow-Ridge High-Power Laser Diodes Using a Double Stripe Structure

Improved Far-Field Angle in Narrow-Ridge High-Power Laser Diodes Using a Double Stripe Structure

New Highly Reliable Optical Transmitting Modules Based on High-Power Superluminescent Diodes in the Spectral Range of 1.5–1.6 μm

New Highly Reliable Optical Transmitting Modules Based on High-Power Superluminescent Diodes in the Spectral Range of 1.5–1.6 μm

Investigation of the cooling performance of a double-layer liquid-cooled plate with circular arc-shaped flow channels for thermal management of light-emitting diodes

Since the integration and heat flux of high-power light-emitting diodes (LEDs) are continuously increasing in response to the rising demand for illumination, high-power LEDs require a sophisticated thermal management system to ensure stable operation and prolonged service life. In the present work, a double-layer liquid-cooled plate with circular arc-shaped flow channels was developed. Circular arc-shaped flow channels may help the fluid flow against the channels' wall more effectively by preventing the development of eddy and impact flow and minimizing flow resistance. Combining it with the double-layer design may conduct cooling in the hot spot area twice as effectively. Numerical analysis and experimentation were conducted to explore the hydraulic properties and cooling performance of the plate, and the LED chips' arrangement schemes were examined. Water and ethylene glycol solutions with varying mass concentrations are utilized as the working fluids. The pin temperatures and illumination characteristics of LED chips were assessed after being cooled using the created plate at various flow rates. The results demonstrate the advantages of the proposed liquid-cooled plate's flow characteristics and cooling capability. After cooling, the LED chips' pin temperatures may be kept below 50 °C. When the flow rate was increased from 0.03 L/min to 0.18 L/min and the operating power of the LEDs was 300 W, the luminous intensity of the chips rose by 1440–1680 lx. Based on the temperature of the surrounding environment, the appropriate working fluid should be employed in practical applications. Furthermore, when the j/f coefficient is large, less pump work is needed, and the plate cools more effectively. It satisfies the need for a lightweight cooling system because the produced liquid-cooled plate weighs only 200 g.

Design and analysis of a group-III nitride superlattice structure based semiconductor laser diode for blue region emission

The demand for high-power blue laser diodes (LDs) in the range above 2 W has been steadily increasing due to their applications in solid-state lighting, projection displays, high-density optical data storage and underwater communication. However, current designs face limitations in terms of achieving both high power output and efficiency. This work focuses on the design, development and numerical analysis of a blue LD utilizing group-III nitride superlattice structures. The present study aims to overcome design challenges by investigating the fundamental factors affecting the performance of blue LDs based on superlattice InGaN structures through careful device parameter optimization. The results show that our device successfully emits at around 430 nm wavelength and is capable of achieving a differential quantum efficiency of 46.91%, with a maximal optical power output of 2.18 W for 1.71 A of current for a strip width of 15 µm. However, when the strip width is increased to 20 µm, 4.6 W optical power is achieved with 3 A of injection current. Numerical studies are performed with several calibrated physics models and finite-difference time-domain techniques. Our results provide an insight into the potential of using superlattice group-III nitride structures to enhance the performance of blue LDs, opening up new possibilities for high-power and high-efficiency devices in the future.

Titanium boride coating by high power diode laser alloying of amorphous boron with titanium and its surface property investigations

Present work deals with fabrication of superhard titanium boride coating on titanium surface with preplaced amorphous boron layer using high power diode laser alloying. Amorphous boron instantaneously converts into crystalline boron by the effect of high-power laser interaction, which rapidly drives the boron species into titanium liquid pool and form titanium boride precipitates by its convective flow. Negative Gibbs free energy (ΔG) and enthalpy (ΔH) of amorphous boron crystallization reaction introduces the concept of laser induced self-propagation synthesis. Gibbs free energy (ΔG) for the chemical reactions between Ti and B was calculated to confirm the spontaneous formation of titanium boride compound phases. The diffusion coefficient and activation energy were estimated to understand the phase formation and microstructural evolution. The structural phase, microstructure, microhardness and wear resistance of the laser borided titanium was investigated by XRD, optical and scanning electron microscopy, EDAX, Vickers microhardness analysis and linear reciprocating wear testing. The laser alloyed coating across the cross section shows formation of dendrites and whisker like microstructures. Average microhardness of 800–1600 HV0.2 was measured at different cross-sectional depths and an extreme hardness of about 3800–4700 HV0.2 was obtained in some regions of boron precipitates. The results showed a high negative value of Gibbs free energy of about −250 kJ/mol and −170 kJ/mol at ∼2000 °C respectively which confirms the spontaneity of TiB2 and TiB phase formation. The activation energy of the titanium boride is estimated to be 140 kJ/mol. The laser borided coating with the formation of TiB and TiB2 phases could be useful for surface engineering applications.

In-Situ early anomaly detection and remaining useful lifetime prediction for high-power white LEDs with distance and entropy-based long short-term memory recurrent neural networks

High-power white light-emitting diodes (LEDs) have demonstrated superior efficiency and reliability compared to traditional white light sources. However, ensuring maximum performance for a prolonged lifetime use presents a significant challenge for manufacturers and end users, especially in safety–critical applications. Thus, identifying functional anomalies and predicting the remaining useful lifetime (RUL) is of enormous importance in the operational longevity of the device. To address such challenges, this study proposes a combination of distance-based Mahalanobis distance (MD), entropy generation rate (EGR), and deep learning models for improved anomaly detection and RUL prediction accuracy. Unlike conventional health indicators based on luminous flux data that are challenging to monitor relevant optical performance, the MD and EGR methods are employed to extract in-situ monitored thermal and electrical data as new health indicators. Long short-term memory recurrent neural networks (LSTM-RNN) and convolutional neural networks (CNN) are established to detect anomalies and predict the RUL. The accelerated degradation tests of 3 W high-power white LED have been conducted, and the online and offline collected experimental data are deployed for model development and performance evaluation. The performance of the proposed methods is compared against the Illuminating Engineering Society of North America (IESNA) TM-21 method. The results indicate that LSTM-RNN, when combined with either MD or EGR, can detect anomalies with significantly fewer data (70 %) than is typically required. Furthermore, a significant improvement in prediction accuracy in RUL prediction based on MD and EGR-constructed time series health indicators and employed with the LSTM-RNN model demonstrates the effectiveness of the proposed methods.

Spatial uniformity of the spectral radiance by white LED-based K<sub>2</sub>CaP<sub>2</sub>O<sub>7</sub>:Ce<sup>3+</sup>, Tb<sup>3+</sup> phosphor

The K2CaP2O7:Ce3+, Tb3+ (Ce/Tb-KCPO) phosphor with blue-to-green emission is introduced in this study. The synthesis of the phosphor is carried out with the solid-state approach. The phosphor characteristics, including X-ray diffraction, luminescence lifespan, and thermal stability are measured and examined. The data show that Ce/Tb-KCPO phosphor displays a broadband emission from blue to green when excited by ultraviolet source. Besides, the ion Ce3+ strengthen the emission of Tb3+ ion through an efficient energy-transfer mechanism, which is estimated about 82.51%. The main electric interaction responsible for this Ce/Tb energy transfer is the dipole-quadrupole one. The phosphor also benefits the luminous intensity and color uniformity of the light-emitting diodes (LED) white-light output. Therefore, the Ce/Tb-KCPO phosphor can be a potential material for high-power white light-emitting diodes (WLED).