Search Results (729)

High-power-density LEDs can achieve many functions that are difficult for traditional light sources and conventional LEDs to realize, pushing the semiconductor lighting technology chain to a new level. Increasing the number of chips is an effective approach to improving the light output capability of LED devices. In this study, five high-power-density LED devices with different chip numbers (4, 9, 16, 25, and 64 chips) were fabricated using the same blue LED chips, and the effects of chip number on the light output capability, spatial light distribution characteristics, and spatially correlated color temperature distribution characteristics of high-power-density LED devices were systematically investigated. The temperature distribution characteristics of the internal chips were further analyzed in combination with infrared thermal imaging results. The results show that increasing the chip number significantly enhances the total light output capability of the device; however, due to the influence of thermal coupling among chips, the saturation current and saturated luminous intensity of devices with different chip numbers are not proportional to the chip number. Increasing the number of chips in the device does not alter the intrinsic spatial emission pattern. Under optical saturation conditions, the luminous intensity distribution curves of all five devices exhibit Lambertian spatial light distribution characteristics. In terms of correlated color temperature, the CCT of all devices increases with increasing current per chip, and devices with more chips exhibit higher CCT values and a faster increasing trend. The spatial CCT distribution results show that the correlated color temperature of the device reaches its maximum in the normal direction, decreases with increasing testing angle, and exhibits good spatial symmetry. The thermal imaging results show that devices with more chips exhibit higher average chip temperatures and a relatively more uniform temperature distribution, which improves the spatial CCT uniformity of the device to some extent. Full article

This study proposes a 300 W class Gallium Nitride (GaN) Solid-State Power Amplifier (SSPA)-based microwave plasma generator system for implementing next-generation light sources with high brightness and color rendering at 2.45 GHz. To overcome the lifetime limitations and control constraints of conventional magnetron systems, the proposed system introduces custom packaging technology utilizing GaN-on-SiC Bare-dies fabricated via the Win-semiconductor’s NP25 process. This approach minimizes parasitic components and significantly reduces thermal resistance compared to standard packages, ensuring reliability during high-power operation. A stable RF output of 300 W was achieved through two-stage power combining. For the plasma source, an Ar-InBr-Hg gas mixture was employed to optimize optical characteristics. This gas mixture is commonly used in electrodeless plasma lamps due to its high luminous efficacy and stable discharge characteristics. To analyze the rapid impedance discontinuity during gas ignition, numerical analysis based on the Drude model was performed, theoretically identifying the complex permittivity transition of the medium and the resulting resonant frequency up-shift mechanism. To mitigate system instability during this transition, an adaptive frequency tracking and feedback control loop based on real-time VSWR monitoring was implemented. Experimental results demonstrate precise tracking within a 100 MHz frequency variable range, achieving a system efficiency of over 53% and maintaining a VSWR below 1.15:1. These results validate the practical feasibility of GaN SSPA technology in electrodeless lighting and industrial plasma applications utilizing high-power RF energy. Full article

Optical coherence tomography (OCT) is a non-invasive, high-resolution imaging technique widely used in medical diagnosis, biomedical research and other fields. It plays an important role in the early detection and accurate diagnosis of diseases. The superluminescent light-emitting diode (SLED) is the ideal light source for OCT systems, where the stability of its drive current and operating temperature directly determines the imaging quality of OCT. Existing driving and temperature control schemes for similar light sources predominantly rely on microcontrollers or field programmable gate arrays (FPGAs), a reliance which often results in complex system architectures and difficulties in balancing simplicity with control precision. To address these issues, a stable and compact SLED source driver module designed for OCT was developed in this study, integrating both a constant-current drive circuit and a temperature control circuit. The negative feedback control and improved current-limiting protection are employed in the constant-current drive circuit to maintain stable SLED operation and reduce the circuit footprint. A miniature dedicated temperature control chip is adopted in the temperature control circuit. The operating temperature of the SLED is acquired by linearizing the negative temperature coefficient (NTC) thermistor value and regulated through a proportional-integral-derivative (PID) compensation circuit. The size of the fabricated module (including casing) is less than 10 × 8 × 3 cm³. Experimental results show that the driver module achieves a drive current control accuracy of 0.1% and a temperature control accuracy of 0.01 °C. The output optical power fluctuation is less than 0.005 mW and the average axial resolution for OCT is 6.5992 μm with a standard deviation of 0.0107 μm. This light source driver module successfully balances control precision with structural simplicity, demonstrating excellent applicability in OCT systems. Full article

Inspired by the growing demand for small and effective optoelectronic devices, this paper presents a simulation-based analysis of InGaN/GaN quantum dot light-emitting diode, focusing on the effects of systematic variation in both anode and cathode contact regions, as well as overall device size. Two-dimensional simulations using APSYS software were used to examine the impact of scaling the device dimensions as well as the individual contact dimensions on significant performance parameters like internal quantum efficiency (IQE), optical output power, and current-voltage (IV) response. We simulated five LED device sizes that is 50 × 50 µm², 100 × 100 µm², 200 × 200 µm², 300 × 300 µm², and 400 × 400 µm². As device size grows, so does the total current at each voltage. The highest current measurement is achieved by the device with dimensions 400 × 400 µm² while the lowest is observed on the device with dimensions 50 × 50 µm². In addition to changing the device dimensions, we ran extensive simulations on the sizes of p-type and n-type contacts. Notable changes were seen in the efficiency, optical power, and emission profile of the p-contact. The behavior of p-side contacts from 0 to 50 µm was the same, while contacts between 60 and 100 µm showed significant differences. The significant performance parameters were unaffected by changes to n-contact dimensions. The results of this study illustrate how the configuration of contacts and dimensions greatly influences the electrical and optical performance of quantum dot light-emitting diode. The results are believed to be helpful to researchers working on the design of next-generation compact and efficient solid-state lighting devices. Full article

This paper presents the concept of a 2D m × n waveguide-based power combiner (PC) that is scalable with respect to the operating frequency band and number of input ports. To our knowledge, this work reports the first planar (2D) power combiner, where the input waveguide ports are distributed in two spatial dimensions to form an array, rather than arranged along a single linear (1D) axis as in conventional corporate or cascaded waveguide combiners. The novelty of the approach relies on using H-plane rectangular waveguide T-junctions and low-loss polarization twisters in between vertically stacked T-junctions to facilitate scalability. The work is motivated by the aim to coherently combine the output power of multiple modified uni-traveling carrier (MUTC) terahertz (THz) waveguide photodiodes (PDs) in a 2D array configuration. In the manuscript, the design of a 2 × 2 planar waveguide power combiner for the WR3 band (220–320 GHz) is reported, and it is also shown that this block can be further extended to m × n input ports. Full-wave numerical analysis of the proposed 2 × 2 power combiner shows a return loss of 11 dB at the output port and an average transmission coefficient of about −6.5 dB, i.e., an overall power combining efficiency of ~90%. Furthermore, to enable 2D photodiode array integration, the manuscript presents a new slot-bow tie antenna integrated MUTC photodiode for radiating the optically generated THz power from each PD vertically into the rectangular waveguide. The simulation results of reflection loss and insertion loss for the slot bow-tie antenna are shown to be better than 10 dB and 1.4 dB over the full WR3 band, respectively. To prove scalability of the power combiner concept w.r.t. the number of input ports, a 2 × 4 power combiner is also analyzed. Results reveal a return loss better than 10 dB from 225 to 318 GHz and a transmission coefficient of approximately −9.7 dB at 300 GHz, i.e., a power combining efficiency of ~85%. Full article

The object of this research is resource management and energy consumption processes in optical fiber communication networks with access–metro–core architectures. The study addresses the problem that conventional static and semi-dynamic control methods are unable to simultaneously ensure energy efficiency and QoS stability under conditions of exponentially growing and highly variable traffic. To solve this problem, an AI-based integrated control model was developed that combines traffic prediction, dynamic resource allocation, spectrum management, and power optimization within a unified framework. Traffic prediction is performed using LSTM–BiRNN neural networks (1.2–1.8 million parameters, 300–500 thousand records), while control decisions are generated by an Actor–Critic reinforcement learning algorithm. Simulation results obtained in the Python 3.12 and OptiSystem 17.0 environments demonstrate that, in the Access segment (1–10 Gb/s), latency is stabilized within 1–10 ms; in the Metro segment (40–120 Gb/s), energy consumption is reduced by 18–27%; and in the Core segment (400–1000 Gb/s), the efficiency of RSA algorithms increases by 22–35%. When the EDFA output power is maintained within +17 to +23 dBm, amplifier power consumption decreases by 10–15%, resulting in overall network energy savings of 20–40%. The obtained results are explained by the synergy of accurate traffic prediction provided by the LSTM–BiRNN model and proactive real-time decision-making enabled by the Actor–Critic algorithm. The distinctive feature of the proposed approach is the simultaneous optimization of energy efficiency and QoS across all access, metro, and core segments within a single integrated architecture. The results can be practically applied in the design and modernization of optical fiber communication networks, as well as in the deployment of energy-efficient intelligent network management systems. Full article

The Nd:GYSAG crystal enables multi-wavelength near-infrared laser output, with adjustable wavelengths tailored for specific application requirements, making it highly valuable for space-borne water vapor detection. This study reports, for the first time, the side-pumping characteristics and electro-optical Q-switching performance of this crystal. Using Ø3 × 73 mm and Ø4 × 73 mm crystal rods doped with 1.21 at.% Nd:GYSAG (chemical formula Nd_0.033Gd_0.93Y_1.79Sc_0.70Al_4.54O_11.99), 1060.4 nm laser output was achieved under 808 nm laser diode (LD) side-pumping at a repetition rate of 100 Hz and a pump pulse width of 250 μs. The experimental results show that the Ø4 × 73 mm rod had a higher laser threshold but exhibited significantly superior slope efficiency and maximum output power compared to the Ø3 × 73 mm rod. Using a flat–flat resonator, optimal laser performance was obtained with an output coupler transmission of 35%, yielding a slope efficiency of 37.2%. A maximum output energy of 179.4 mJ was achieved at a pump energy of 646 mJ. Thermal lensing effects were compensated using a flat–convex cavity, leading to improved laser performance and beam quality. Electro-optical Q-switching experiments were conducted using a KD*P crystal. A comparison between voltage-applied and voltage-removed Q-switching techniques revealed superior performance for the voltage-applied method. High-performance laser output was realized, achieving a maximum pulse energy of 59.6 mJ, a pulse width of 14.93 ns, and a peak power of 3.99 MW. This study provides an important foundation for the development of near-infrared laser devices based on Nd:GYSAG. Full article

Photonic-crystal surface-emitting lasers (PCSELs) are a new type of semiconductor laser with the potential for high-power output and high-beam-quality operation. Integrating a distributed Bragg reflector (DBR) into PCSELs can significantly enhance device performance. However, the growth of high-aluminum-content DBRs on photonic crystal layers with buried air holes presents two major challenges. First, the low mobility of aluminum atoms increases the propagation of surface roughness from the substrate into the DBR, increasing defect density. Second, the high growth temperatures required for DBR growth can deform the thermally unstable air holes. In this work, we investigated a metal–organic chemical vapor deposition (MOCVD) regrowth process for fabricating DBRs on PCSELs. By adjusting the epitaxial growth temperature and V/III ratio, we effectively controlled the diffusion of adatoms on both the sample surface and inside the holes. As a result, the root mean square (RMS) surface roughness decreased by ~96%, and uniform buried air holes were obtained, with a filling factor of ~ 18.8% and a depth of ~ 270 nm, without significant deformation. Finally, we fabricated a PCSEL device with a DBR structure, exhibiting a beam divergence angle of ~ 0.5° and a peak power of about 0.86 W. This study provides a key process solution for the development of PCSELs with high-quality DBR structures, enabling further improvement in optical output performance. Full article

Clouds are a key factor affecting solar radiation, and their dynamic variations directly cause uncertainty and fluctuations in photovoltaic (PV) power output. To improve PV power prediction accuracy, this paper proposes an enhanced short-term photovoltaic power forecasting approach based on a hybrid neural network architecture using features extracted from satellite cloud images. First, a dual-layer image fusion method is developed for satellite cloud images from different wavelengths and spectral bands, effectively improving fusion accuracy. Second, texture descriptors derived from the Gray-Level Co-occurrence Matrix and multiscale information obtained via the wavelet transform are employed for feature extraction from fused images. Combined with a residual network (ResNet), an optical flow method, as well as an LSTM-based temporal modeling module, multidimensional features of the predicted cloud images are obtained. An improved Bayesian optimization (IBO) algorithm is then employed to derive the optimal fused features, thereby improving the matching between cloud image features and PV power. Third, an enhanced hybrid architecture integrating a convolutional neural network and long short-term memory units with a multi-head self-attention mechanism is developed. Numerical weather prediction (NWP) meteorological features are incorporated, and a tilted irradiance model is introduced to calculate the solar irradiance received by PV modules for use in near-term photovoltaic power forecasting. Finally, measurements collected at a photovoltaic power plant located in Hebei Province are used to validate the proposed method. The results show that, relative to the SA-CNN-MSA-LSTM and BO-CNN-LSTM models, the developed approach lowers the RMSE to an extent of 22.56% and 4.32%, while decreasing the MAE by 24.84% and 5.91%, respectively. Overall, the proposed model accurately captures the characteristics of predicted cloud images and effectively improves PV power prediction accuracy. Full article

Photobiomodulation (PBM) has shown promising potential to enhance bone regeneration; however, its optimal delivery parameters and interactions with osteoconductive scaffolds remain insufficiently defined. This preclinical study is the first to incorporate a pilot dosimetry evaluation to standardize 980-nm PBM delivery and ensure that effective irradiance reached the target surface of critical-size calvarial defects in mice. The primary aim was to evaluate the effectiveness of this novel 980-nm PBM protocol delivered using either flat-top (FT) or standard Gaussian (ST) handpieces in enhancing bone regeneration in critical-size defects (CSDs), both with and without Bio-Oss^® grafting. A total of 120 adult mice were allocated into twelve experimental groups (n = 10 per group): untreated (control), Bio-Oss^® alone, PBM alone, and PBM combined with Bio-Oss^®, using either FT or ST handpieces, and evaluated at 30 and 60 days. Animals received 980 nm irradiation at 0.6 W (nominal power output–set on laser interface) in continuous-wave mode for 60 s, three times per week, for two consecutive weeks. Pilot dosimetry included power meter measurements to determine the therapeutic power reaching the defect surface area and temperature monitoring to ensure safe energy delivery. The dosimetry study demonstrated that, after accounting for the optical properties of mouse shaved skin and the Bio-Oss^® graft covered with Bio-Gide^® membrane, the effective irradiance reaching the base of the defect surface area was 1.131 W/cm² for the FT handpiece and 0.413 W/cm² for the ST handpiece. This dose was sufficient to induce significant regenerative effects. Histological, Masson’s trichrome, and immunohistochemical analyses for Runx2, OCN, GLI1, CD34, and CTSK were performed to characterize early and late osteogenic events. The combination of PBM and Bio-Oss^® significantly accelerated bone regeneration compared with PBM alone, with the FT handpiece producing the most uniform and advanced osteogenesis. PBM enhanced progenitor activation, osteoblast differentiation, angiogenesis, matrix deposition, and late-stage remodeling, demonstrating a synergistic effect with the scaffold, whereas Bio-Oss^® alone or defect alone showed limited early regenerative potential. These findings highlight the effectiveness of this novel standardized PBM dosimetry and uniform beam profile (FT), supporting their use as a foundation for future randomized controlled trials in craniofacial bone repair. Full article

Multijunction laser power converters are demonstrated for the first time with high efficiencies for average optical irradiances exceeding 150 W/cm². The GaAs-based photovoltaic power converting III-V heterostructures are designed with six GaAs subcells having an area of 0.14 cm², receiving up to 22 W of input power at ~811 nm, delivering over 14 W of output power. The maximum efficiencies are obtained in the range of 30 to 75 W/cm², and efficiencies > 64% are still obtained at 160 W/cm². The efficiency reduction for higher irradiance values originates predominantly from residual heat generated in the active layers. For example, in 100% duty factor measurements, the bandgap voltage offset saturates to W_oc ~ 170 mV. However, in pulsed mode, W_oc values as low as 150 mV have been obtained for a device base temperature of 20 °C. For smaller 0.029 cm² devices, W_oc values around 137 mV are obtained at 240 W/cm². Full article

Laser-based manufacturing processes—including marking, hardening, cutting, and welding—demand the precise selection of processing parameters, as the resulting surface state is critically dependent on the delivered power density and beam–material interaction time. This study presents a unified predictive framework for estimating the critical surface power density thresholds for melting q_scm and evaporation q_scv as functions of scanning speed v for the following four technologically important metallic materials: titanium, C26000 brass, SS304 stainless steel, and 42CrMo4 alloy steel. The principal novelty of this work is twofold. First, it provides the first directly comparative analysis of these four materials under identical, standardized laser conditions (λ = 1064 nm, d = 40 μm, constant absorptivity A = 0.4), eliminating the confounding effects of variable beam geometries and optical assumptions that hinder cross-study comparisons. Second, it translates fundamental thermophysical principles into a practical engineering tool, such as a validated spreadsheet calculator that outputs material-specific threshold curves in real time, enabling rapid, physics-based parameter estimation without recourse to complex numerical simulations. The computed threshold curves exhibit a consistent non-linear increase with scanning speed for all materials, governed by the inverse relationship between interaction time and required power density. The following clear material hierarchy emerges: C26000 brass exhibits the highest thresholds (e.g., q_scm = 0.94 × 10¹⁰ W/m², q_scv = 10.74 × 10¹⁰ W/m² at v = 100 mm/s) due to its high thermal conductivity, while titanium shows the lowest (q_scm = 0.19 × 10¹⁰ W/m², q_scv = 0.48 × 10¹⁰ W/m² at v = 100 mm/s) as a consequence of strong heat confinement. SS304 and 42CrMo4 occupy intermediate positions, with 42CrMo4 demonstrating notably higher evaporation resistance than SS304 despite similar melting thresholds. The resulting dual-threshold framework delineates three distinct process regimes—sub-melting heating, melting-dominant processing, and evaporation—providing a quantitative basis for parameter selection in applications ranging from surface hardening to micromachining. By bridging the gap between theoretical material science and applied manufacturing, this work offers a robust, first-order reference for process design and establishes a methodological template for future comparative studies of laser–material interactions. Full article

The 6.45 μm mid-infrared laser is highly promising for medical applications due to its efficient tissue ablation with minimal collateral damage. In this work, we demonstrate a stable and compact 10W-level, all-solid-state nanosecond laser source at 6.45 μm based on a Ho:YAG MOPA pumped ring-cavity ZnGeP2 optical parametric oscillator (ZGP OPO). The influence of spot size, phase-matching scheme, and crystal length on the output performance was systematically investigated. Using a 30 mm long Type I ZGP crystal, the system achieved optimal performance: a record-high average output power of 14.6 W at 6.45 μm with an optical-to-optical conversion efficiency of 17.57%, a peak power of 51.7 kW, and excellent power stability (1.45% fluctuation over 120 min at 11.7 W). To our knowledge, this represents the highest reported output power and conversion efficiency for an OPO in this spectral region, surpassing previous sources by an order of magnitude in average power and showing nearly double efficiency. This work provides a stable and reliable laser source tool for application research for techniques such as laser ablation. Full article

This article investigates fiber coupling techniques for low numerical aperture 808 nm semiconductor lasers. A coupling optical system combining fast-axis/slow-axis collimators (FAC/SAC) with a focusing lens was designed, achieving efficient coupling through high-precision optical integration packaging. First, a high-power GaAs-based 808 nm semiconductor laser chip was designed and fabricated. Its thermal performance and operational stability were enhanced by optimizing packaging materials and structures. The coupling system employs a fast-axis collimating lens, slow-axis collimating lens, and aspheric focusing lens to shape the beam and focus it into a 200 μm/0.12 NA fiber. Experimental results show that the developed coupling module achieves the threshold current of 1.2 A at 298 K, the continuous output power of 9.59 W, with the slope efficiency of 1.1 W/A, a coupling efficiency of 95%, the maximum output numerical aperture of 0.116, the wavelength temperature drift coefficient of approximately 0.2 nm/°C, and the peak brightness of 0.72 MW/cm²·sr. This study validates the feasibility and superiority of the FAC/SAC combined with focusing lens approach for low-NA fiber coupling. It provides theoretical and practical foundations for fiber coupling in high-brightness, high-power laser systems, offering promising applications in solid-state laser pumping, enhancing system integration, and enabling long-distance, high-brightness transmission. Full article

The 1626 nm laser is an essential component for conducting superlattice research on the strontium atomic clock platform. The superlattice constructed with the 1626 nm and 813 nm lasers will facilitate cutting-edge quantum information research focused on topological quantum states transport. We demonstrate an idler-resonant optical parametric oscillator that achieves 1626 nm laser output based on pump enhancement technology. Through a well-designed external cavity, a laser output of 127 mW at 1626 nm has been achieved, with a corresponding pump quantum conversion efficiency of 50% and a pump threshold of 110 mW. The long-term power stability of the output laser is ±1.5% per hour. Variations in the pump cavity modes under different experimental conditions have been measured, and the impedance matching process of the pump light within the cavity has been discussed. The 1626 nm laser and the associated technologies reported in this manuscript will provide optical support for the investigation of superlattice physics on the strontium optical lattice clock platform. Full article