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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - Underwater Wireless Optical Communications at 100 Mb/s using Integrated Dual-Color Micro-LEDs
摘要： Integrated blue-violet and blue-green micro-LED arrays, fabricated via a transfer printing method, were employed to demonstrate wavelength division multiplexing underwater data transmission at 100 Mb/s over up to 9 attenuation lengths in a 1.5 m long water tank.
关键词： UWOC,VLC,micro-LED,WDM,transfer printing,turbid
更新于2025-09-11 14:15:04
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A Turn-off Delay Controlled Bleeder Circuit for Single-Stage TRIAC Dimmable LED Driver With Small-Scale Implementation and Low Output Current Ripple
摘要： A single-stage TRIAC (TRIode for Alternating Current switch) dimmable LED (Light Emitting Diode) driver using a buck converter fed through a capacitor input rectifier provides many advantages such as small-scale implementation, low output current ripple, and stable dimming operation. This circuit topology, however, has a serious issue: a large inrush current to the smoothing capacitor. To solve this issue, this paper focuses on a bleeder circuit in the TRIAC dimmable LED driver. This paper presents the mechanism of the large inrush current issue and its relationship to a conventional bleeder circuit. Moreover, this paper proposes a turn-off delay controlled bleeder circuit. The proposed bleeder circuit is analyzed by using its discrete-time state-space model in order to set proper circuit parameters for inrush current reduction. Experimental results demonstrate the inrush current reduction by the proposed method, which leads to a 37 % reduction of maximum input current, as well as proper dimming operation and low output current ripple. The proposed method achieves further small-scale implementation, which enhances the advantages of the intended main circuit topology.
关键词： single-stage topology with capacitor input rectifier,LED driver,bleeder circuit,discrete-time state-space model,TRIAC dimmable
更新于2025-09-11 14:15:04
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InGaN based tunable green light-emitting diodes using InAlN interlayer and strain compensated AlGaN interlayer for better device performance
摘要： The effect of employing an InyAl1?yN and AlyGa1?yN interlayer (IL) in the InxGa1?xN/GaN active region for the green light-emitting diodes (LEDs) has been studied. The high compressive strain in InxGa1?xN/GaN QW is compensated by the tensile strained AlyGa1?yN IL. The InyAl1?yN IL reduces the strain between InxGa1?xN and GaN layers. The AlyGa1?yN or the InyAl1?yN layer in between the QW and the GaN barriers increase the barrier height, which potentially suppresses the electron and hole leakage from the QW. These increase the square of the overlap of electron and hole wave functions (M )eh of the QW LEDs. By changing the well width and aluminum or indium content in the IL, we obtained better optical properties. It has found that 10 ? thick In0.2Al0.8N and 10 ? thick Al0.8Ga0.2N layers give the maximum Meh for the green LEDs, using InyAl1?yN and AlyGa1?yN ILs. Furthermore, we have compared the Meh, using AlyGa1?yN and InyAl1?yN IL with the current. The best result is obtained for the 10 ? Al0.8Ga0.2N IL, which increases the Meh up to 2 times, as compared to the QW LEDs, without any IL.
关键词： AlyGa1?yN interlayer,InxGa1?xN QW LED,InyAl1?yN interlayer,Transition energy
更新于2025-09-11 14:15:04
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Pyrolysis‐Synthesized g‐C <sub/>3</sub> N <sub/>4</sub> /Nb <sub/>2</sub> O <sub/>5</sub> Nanocomposite for Enhanced Photocatalytic Activity under White LED Light Irradiation
摘要： The design and fabrication of highly active visible-light-driven photocatalysts have been received considerable attention in recent years. However, individual component-based photocatalysts are limited in their use because of the high recombination of photoinduced carriers and poor chemical stability. Herein, the Z-scheme-originated photocatalytic activity of in-situ deposited Nb2O5 NPs on the plane surface of carbon nitride (g-C3N4) nanosheets (i. e. CN-NbO) heterostructures was studied using a simple thermal pyrolysis method. The as-synthesized photocatalysts distinctly manifested efficient white light-emitting diode (LED) irradiation toward organic malachite green (MG) dye degradation and photocatalytic hydrogen generation. The CN-NbO heterostructure showed a faster degradation rate of the MG dye and a higher photocatalytic hydrogen evolution rate. In addition, the plausible Z-scheme photocatalytic mechanism for photocatalytic hydrogen production under LED light irradiation was discussed. Photoelectrochemcial studies showed that the superior photoactivity of CN-NbO heterostructure is mainly a result of the suitable alignment of the band edge positions, which diminish carrier recombination and facilitate efficient interfacial charge transport at their interface. This study provides an ideal method for in-situ fabrication of novel two dimensional/one dimension-based photocatalysts with high activity and stable performance for photocatalytic hydrogen generation.
关键词： Dye degradation,Hydrogen evolution,Nanoparticles,Photocatalyst,LED irradiation,Layered materials
更新于2025-09-11 14:15:04
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Investigating the Effects of Different LED Wavelengths on Aggregation and Swimming Behavior of Chub Mackerel (Scomber japonicus)
摘要： Efficient fish aggregation systems are essential for catching chub mackerel (Scomber japonicus), which is a major target of purse seine fisheries in South Korea. To aid the development of such systems, this study used a Dual frequency IDentification SONar acoustic camera and a visual camera to investigate the effects of light emission diode (LED) aggregation systems of different light wavelengths on the frequency of occurrence and swimming behavior of chub mackerel. The experiment was performed using 50 individuals in a circular tank (diameter, 6.0 m × height, 1.5 m). The LED aggregation systems emitted blue light (454 nm), white light (545 nm + 560 nm), yellow light (596 nm), and red light (634 nm). At night, initial swimming speed increased in response to the four LED systems, and stabilized over time. Frequency of occurrence was highest under blue light, followed by yellow light, white light, and red light, in this order, and, according to wavelength at daytime and at nighttime, it was highest under blue light. The swimming speed of the mackerel school showed an increasing trend over time for all LED aggregation systems, and, for blue light, there was a large, rapid increase in swimming speed.
关键词： acoustic camera,LED aggregation,swimming behavior,chub mackerel,wavelengths
更新于2025-09-11 14:15:04
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Cathodoluminescence Enhancement of MoS <sub/>2</sub> by Femtosecond Laser Induced Periodic Surface Structures
摘要： Submicron-sized Er3+ doped Y7O6F9 phosphors were synthesized via the precipitation method and a subsequent annealing process. The influence of the Er3+ doping concentrations and the heating temperature on the luminescence of Y7O6F9:Er3+ was investigated under the excitation of the Er3+ 4G11/2 level at 378 nm. Upon raising the Er3+ doping concentration, both the intensity and lifetime of the Er3+ green emission at 547 nm originating from 4S3/2 - 4I15/2 decrease, which is proved to be caused by energy transfer via cross relaxation between two neighboring Er3+ ions. The thermal sensing properties of Y7O6F9:Er3+ were evaluated using the temperature dependent intensity ratio between the 2H11/2–4I15/2 and 4S3/2–4I15/2 transitions of Er3+ under 378 nm excitation. The experimental results show that the thermal sensitivity decreased with an increase in the Er3+ doping content, which is caused by the increased energy transfer probability among Er3+. The increased energy transfer of Er3+ reduces the thermalized population of Er3+ in the 2H11/2 levels, which in turn decreases the thermal sensitivity. The applicability of Er3+ doped Y7O6F9 as a thermal sensor was demonstrated by measuring the chip temperature of a 1 W InGaN type near-ultraviolet light emitting diode (n-UV LED).
关键词： luminescence,Y7O6F9:Er3+,LED,thermal sensing
更新于2025-09-11 14:15:04
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High Temperature and Power Dependent Photoluminescence Analysis on Commercial Lighting and Display LED Materials for Future Power Electronic Modules
摘要： commercial light emitting diode (LeD) materials - blue (i.e., inGan/Gan multiple quantum wells (MQWs) for display and lighting), green (i.e., inGan/Gan MQWs for display), and red (i.e., Al0.05Ga0.45in0.5p/Al0.4Ga0.1in0.5P for display) are evaluated in range of temperature (77–800) K for future applications in high density power electronic modules. the spontaneous emission quantum efficiency (QE) of blue, green, and red LED materials with different wavelengths was calculated using photoluminescence (pL) spectroscopy. the spontaneous emission Qe was obtained based on a known model so-called the ABc model. this model has been recently used extensively to calculate the internal quantum efficiency and its droop in the III-nitride LED. At 800 K, the spontaneous emission quantum efficiencies are around 40% for blue for lighting and blue for display LED materials, and it is about 44.5% for green for display LED materials. The spontaneous emission QE is approximately 30% for red for display LED material at 800 K. The advance reported in this paper evidences the possibility of improving high temperature optocouplers with an operating temperature of 500 K and above.
关键词： high temperature,LED materials,power electronics,quantum efficiency,photoluminescence
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE Energy Conversion Congress and Exposition (ECCE) - Baltimore, MD, USA (2019.9.29-2019.10.3)] 2019 IEEE Energy Conversion Congress and Exposition (ECCE) - An Energy Efficient Li-Fi Transmitter with Single Inductor Multiple Output LED Driver
摘要： High-Efficiency Light-Fidelity (Li-Fi) transmitter for simultaneous illumination and Visible Light Communications (VLC) using LED lighting is presented in this work. The proposed transmitter is based on Single Inductor Multiple Output (SIMO) buck converter with two independently controllable outputs or channels, namely lighting channel and communications channel for enabling flicker free illumination without affecting high-speed modulation of LEDs. By this approach, power converter switching frequency is decoupled from modulation frequency of LEDs, thereby optimizing SIMO converter switching frequency for efficiency and the VLC modulator frequency for high speed data transfers. GaN devices are used to realize VLC modulator for high speed modulation to further enhance the efficiency. Light output with high Color Rendering Index (CRI) is achieved by controlling white LEDs as primary illumination source at lighting channel and red color LEDs at communication channel. Simulations and experimental results to validate the proposed transmitter are presented.
关键词： Single Inductor Multiple Output Converters,Color Rendering Index(CRI),Light-Fidelity(Li-Fi),High Brightness Light Emitting Diodes(HB-LED),Visible Light Communications (VLC),IoT (Internet of Things)
更新于2025-09-11 14:15:04
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True colors restoring of reconstructed image in naked-eye 3D LED display based on eliminating optical dispersion
摘要： True colors restoring of reconstructed image in naked-eye 3D LED display based on eliminating optical dispersion. Naked-eye 3D LED display is getting more mature with the increase of LED screen density. And the true colors restoring of reconstructed image in integral imaging LED display is a new direction of the research. Herein, when using the micro lens array to perform the white light, 3D integral imaging LED display has serious optical dispersion. We proposed a kind of optical array model in order to eliminate optical dispersion and restore true colors of the reconstructed image. This model can effectively reduce the chromatic aberration and the crosstalk among the lights by decreasing the large divergence angle of LED’s single pixel point. Besides, the resolution of the reconstructed image can be improved simultaneously. Experimental results validated that compared with previous models, the current model can provide effective reduction of dispersion in LED integral imaging, and further analysis verified the feasibility of the proposed method.
关键词： 3D LED display,optical dispersion,true colors restoring,achromatic optical array model,integral imaging
更新于2025-09-11 14:15:04
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High-bandwidth InGaN self-powered detector arrays toward MIMO visible light communication based on micro-LED arrays
摘要： This work reports the use of the chip-based GaN-based micro-LED (μLED) arrays for multifunctional applications as micro-display, data transmitters, photodetectors and solar cells. The functions of display and transmitter have been reported, and particularly we experimentally demonstrated that μLED arrays could be used as self-powered, high-performance and wavelength-selective photodetectors (PDs) enabling high-speed multiple-input multiple-output (MIMO) visible light communications (VLC) under on-off keying (OOK) modulation scheme using 405 nm violet laser diodes (LDs) as transmitters. The optoelectronic and communication characteristics of the μLED-based PDs with diameters of 40 μm, 60 μm and 100 μm were systematically studied. The optoelectronic analysis shows superior performances of μLED-based PDs at 405 nm wavelength compared with other previously reported GaN-based PDs. Under a bias voltage of -5 V, the comparable peak responsivities of 0.27, 0.31 and 0.24 A/W, specific detectivities of 1.1 × 1011, 2.3 × 1012 and 2.1 × 1012 cm ? H1/2 ? W-1, and linear dynamic ranges (LDRs) of 152, 162 and 164 dB were achieved for 40-μm, 60-μm and 100-μm μLEDs, respectively. Even at zero-bias, i.e. self-powered mode, we have achieved high peak responsivities of 0.24, 0.29 and 0.21 A/W, high specific detectivities of 7.5 × 1012, 1.5 × 1013 and 1.3 × 1013 cm?H1/2?W-1 and high LDR up to 186, 196 and 197 dB for 40-μm, 60-μm and 100-μm μLEDs, respectively. The μLEDs could also be used to harvest the optical energy of the system, working as solar cells. The μLED-based PD arrays were tested as receivers in VLC system to implement high-speed parallel communication, which yields maximum data rates of 180 Mbps, 175 Mbps and 185 Mbps for a single 40-μm, 60-μm and 100-μm μLED-based PDs at a distance of 1 m with BERs of 3.5 × 10-3, 3.7 × 10-3 and 3.5 × 10-3, respectively. Furthermore, 2 × 2 MIMO parallel VLC system was achieved to increase the VLC data rate, which suggests the potential of using large μLED-based PD arrays for multiple Gbps and even Tbps VLC applications.
关键词： photodetector array,visible light communication,Micro-LED (μLED),multiple-input and multi-output (MIMO),self-powered
更新于2025-09-11 14:15:04