This PDF file contains the front matter associated with SPIE Proceedings Volume 10378, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

Low energy use and reduced maintenance have made the LED, a solid-state light (SSL) source, the preferred technology for many lighting applications. With the explosion of products in the marketplace and subsequent price erosion, manufacturers are looking for lower cost materials and manufacturing methods. 3-D printing, also known as additive manufacturing, could be a potential solution. Recently, manufacturers in the automotive, aerospace, and medical industries have embraced 3-D printing for manufacturing parts and systems. This could pave the way for the lighting industry to produce lower cost, custom lighting systems that are 3-D printed on-site to achieve on-time and on-demand manufacturing. One unique aspect of LED fixture manufacturing is that it requires thermo-mechanical, electrical, and optical components. The goal of our investigation was to understand if current 3-D printing technologies and materials can be used to manufacture functional thermo-mechanical, electrical, and optical components for SSL fixtures. We printed heat sink components and electrical traces using an FFF-type 3-D printer with different filaments. The results showed that the printed heat sinks achieved higher thermal conductivity values compared to components made with plastic materials. For electrical traces, graphene-infused PLA showed low resistivity but it is much higher than bulk copper resistivity. For optics, SLA-printed optical components showed that print resolution, print orientation, and postprocessing affect light transmission and light scatter properties. Overall, 3-D printing offers an opportunity for mass customization of SSL fixtures and changing architectural lighting practice, but several challenges in terms of process and materials still have to be overcome.

In the frame of EUCLID project, the Calibration Unit of the VIS (VISible Imager) instrument must provide an accurate and well characterized light source for in-flight instrument calibration without noise when it is switched off. The Calibration Unit consists of a set of LEDs emitting at various wavelengths in the visible towards an integrating sphere. The sphere’s output provides a uniform illumination over the entire focal plane. Nine references of LEDs from different manufacturers were selected, screened and qualified under cryogenic conditions. Testing this large quantity of samples led to the implementation of automated testing equipment with complete in-situ monitoring of optoelectronic parameters as well as temperature and vacuum values. All the electrical and optical parameters of the LED have been monitored and recorded at ambient and cryogenic temperatures. These results have been compiled in order to show the total deviation of the LED electrical and electro-optical properties in the whole mission and to select the best suitable LED references for the mission. This qualification has demonstrated the robustness of COTS LEDs to operate at low cryogenic temperatures and in the space environment. Then 6 wavelengths were selected and submitted to an EMC sensitivity test at room and cold temperature by counting the number of photons when LEDs drivers are OFF. Characterizations were conducted in the full frequency spectrum in order to implement solutions at system level to suppress the emission of photons when the LED drivers are OFF. LEDs impedance was also characterized at room temperature and cold temperature.

We have developed an innovative lighting system prototype for a patient room application that integrates a multi-channel luminaire platform into indoor general area luminaires. This system is energy efficient, spectrally tunable, and supports the visual and nonvisual needs of occupants. We evaluated the performance of two separate multichannel platforms in different luminaire types, using a unique color-processing algorithm. The LED modeling and simulations enabled optimization of spectral power distributions, color, light output, and efficacy. This paper discusses the complicated results of SPDs developed for the patient room application, especially how they are effective for positively supporting the human visual and non-visual (circadian) systems. Additionally, application measurements demonstrate the large impact of the application space on the resulting SPD of a luminaire, calling into question the feasibility of using traditional field measurements to validate luminaire performance.

High power LEDs (HP-LEDs) are key building blocks of solid-state lighting products, therefore, it is important for LED manufacturers, lamp/luminaire manufactures, and testing/calibration laboratories to measure their optical and electrical properties with high accuracy. Measuring HP-LEDs has been difficult because they are highly sensitive to their junction temperatures, which rise rapidly when they are turned on. Various methods have been proposed and used to measure HP-LEDs, but most of them are only useful for particular applications and unable to produce accurate and reproducible measurement results. To address the measurement need, the Illuminating Engineering Society (IES) recently approved three methods that can be used for the measurement of HP-LEDs, which are the DC method, single-pulse method, and continuous-pulse method [1]. All three measurement methods refer to the junction temperature of an HP-LED as the thermal condition and thus, the measured results are considered to be equivalent as long as the junction temperature is set to be the same. However, our recent study shows that the difference in the measurement results of the three different methods can be significant (e.g., 5 % in total luminous flux) due to significant heating of the junction and/or phosphor material of the HP-LED during the period of a measurement. In this paper, we will describe the measurement of HP-LEDs using the three different methods, compare the measurement results, and discuss the cause that results in the significant difference. [1] Illuminating Engineering Society, “IES LM-85-14: Approved Method: Electrical and Photometric Measurements of High-Power LEDs.” (2014)

Color fidelity has been used as one of indices to evaluate the performance of light sources. Since the Color Rendering Index (CRI) was proposed at CIE, many color fidelity metrics have been proposed to increase the accuracy of the metric. This paper focuses on a comparison of the color fidelity metrics in an aspect of accuracy with human visual assessments. To visually evaluate the color fidelity of light sources, we made a simulator that reproduces the color samples under lighting conditions. In this paper, eighteen color samples of the Macbeth color checker under test light sources and reference illuminant for each of them are simulated and displayed on a well-characterized monitor. With only a spectrum set of the test light source and reference illuminant, color samples under any lighting condition can be reproduced. In this paper, the spectrums of the two LED and two OLED light sources that have similar values of CRI are used for the visual assessment. In addition, the results of the visual assessment are compared with the two color fidelity metrics that include CRI and IES TM-30-15 (R_f), proposed by Illuminating Engineering Society (IES) in 2015. Experimental results indicate that R_f outperforms CRI in terms of the correlation with visual assessment.

Pyroelectric radiometers with spectrally constant response have been developed at NIST with the cooperation of a few detector manufacturers. The new devices have noise-equivalent-power (NEP) values less than 1 nW/Hz^1/2 sufficiently low for use at the output of regular monochromators. Their response flatness is an order of magnitude better than that of filtered Si detectors and can be used to realize simple and low-uncertainty responsivity scales for the UV and IR wavelength ranges. For the first time, the UV irradiance responsivity of a pyroelectric detector has been determined. Based on spectral reflectance measurements of the black coating of the pyroelectric detector, the relative spectral response was determined between 0.25 μm and 30 μm. The relative response was then converted into spectral power and irradiance responsivities using absolute tie points from a silicon-trap-detector in the VIS range. In addition to the UV irradiance responsivity scale realization, the flat response between 1.6 μm and 2.6 μm was utilized and a constant irradiance responsivity was realized and applied as a reference scale for the Spectral Irradiance and Radiance Responsivity Calibrations with Uniform Sources (SIRCUS) facility of NIST. The spectral power responsivity of the low-NEP pyroelectric detector is the internal standard of the NIST VIS-IR detector calibration facility for the 0.6 μm to 24 μm wavelength range. The pyroelectric standard is used to calibrate other types of detectors for spectral responsivity using detector substitution. The flat-response interval of the pyroelectric standard, calibrated for irradiance responsivity, was also used to measure the integrated irradiance from UV LED sources without using any source standard. The broadband radiometric measurements can be applied to IR LEDs emitting low fluxes between 750 nm and 4300 nm. All pyroelectric detector based calibrations were performed with expanded uncertainties of about 2 % (k=2).

GaN devices when operated at high powers are limited by excessive temperature rise in the device critical regions. Traditionally SiC, Si or sapphire substrates or homoepitaxy on GaN substrates are used for the growth of GaN device structures, however, the substrate thermal conductivity is rather limited. Diamond substrates with their ultra-high thermal conductivity offer new opportunities for achieving ultra-high power GaN electronic microwave / RF devices, and optoelectronic devices. This is presently being explored within the UK EPSRC research program GaN-DaME.

This contribution will present the structural and optoelectronic properties of GaN/AlGaN heterostructures grown by Metal Organic Chemical Vapor Deposition (MOCVD) on GaN/sapphire templates. The target parameters for the materials heterostructures have been modeled for utilization in Avalanche Photodiode Detector Structures (APD) operating in the near and deep UV region. Optical modeling has improved absorption within the heterojunction as well as maximized light trapping within the device. Electronic modeling has determined the optimal dopant concentrations for maximum impact ionization rate, as well as tolerance to defects and unintentional doping. This application will require advances in the defect densities, surface morphology, and interfaces. Surface morphological and structural properties of GaN/AlGaN heterostructures are analyzed by Atomic Force Microscopy, Raman spectroscopy, and X-ray diffraction. The optoelectronic properties (phonon structures, free carrier concentrations, and carrier mobility) as well as layer thickness information, are determined by Fourier Transform Infrared Reflectance spectroscopy. A correlation of interfacial defects (type and concentration) with microscopic structural properties, surface morphology, and optoelectronic properties (free carrier concentration and high-frequency dielectric function) is discussed.

We performed the simulation and experiment to investigate the influence of Zirconium dioxide (Zirconia, ZrO2) particles on the optical properties of phosphor converted white LED (pcW-LED). An efficient optical model was developed and applied to the incorporation diffuse particle of ZrO2 into a hemisphere package containing YAG phosphors. The optical properties (chromaticity, packaging efficiency) were estimated as a function of phosphor and ZrO2 particles, through the calculation of effective radius, refractive index, and absorption and conversion efficiency, in a range of correlated color temperature 4500 K to 6500 K. In the same way, the amount of phosphor and ZrO2 can be calculated accurately to obtain a targeted optical property in a hemisphere LED design. Especially, the angular distribution of CCT was also diminished, and even almost inexistent for low CCT design. In addition, the adding of ZrO2 particles allows clearly decreasing the amount of phosphor for an identical target CCT. It is really suitable in the context of decreasing the amount of phosphor or in some applications where the color uniformity is an important parameter, like indoor down-lighting.

Light-emitting diodes (LEDs) have been steadily consolidating their share in the lighting and display market. Phosphor-converted (pc) white LED becomes the preferred way to generate white light especially for general lighting, as it is much cheaper and simpler than RGB system. Phosphors are essential to high color quality and luminous efficacy. However, the number of commercially available phosphors is very limited. Therefore, developing new phosphors suitable for various white LED applications is very important. Recently, our group developed the single-particle-diagnosis approach [1-2] to discover new phosphors, with which a tiny luminescent microcrystalline particle down to 5-10 μm can be selected from powder mixtures. In this work, we report a new green emitting Sr-sialon:Eu phosphor discovered by this approach. The crystal structure was solved and refined from single crystal X-ray diffraction data. Sr-sialon:Eu crystallizes in the trigonal space group P3m1 (no. 156) with a = b = 12.1054 Å, c = 4.8805 Å and Z = 1, and consists of a network of corner sharing (Si,Al)(N,O)4 tetrahedra. Upon doping with Eu2+, the emission band can be tuned from 487 nm to 541 nm with fwhm = 96-124 nm. Ce3+ doped Sr-sialon phosphor shows strong blue emission around 435 nm with a fwhm ≈ 90 nm after 355 nm light excitation. The blue luminescence exhibits a small thermal quenching behavior at high temperature. These performances show that the new Eu2+ and Ce3+ doped Sr-sialon phosphors are promising for white LED applications. [1] N. Hirosaki, T. Takeda, S. Funahashi and R.-J. Xie, Chemistry of Materials, 2014, 26, 4280-4288. [2] T. Takeda, N. Hirosaki, S. Funahashi and R.-J. Xie , Materials Discovery, 2015, 1, 29-37.

Combining traditional phosphors with a broad emission spectrum and non-scattering quantum dots with a narrow emission spectrum can have multiple advantages for white LEDs. It allows to reduce the amount of scattering in the wavelength conversion element, increasing the efficiency of the complete system. Furthermore, the unique possibility to tune the emission spectrum of quantum dots allows to optimize the resulting LED spectrum in order to achieve optimal color rendering properties for the light source. However, finding the optimal quantum dot properties to achieve optimal efficacy and color rendering is a non-trivial task. Instead of simply summing up the emission spectra of the blue LED, phosphor and quantum dots, we propose a complete simulation tool that allows an accurate analysis of the final performance for a range of different quantum dot synthesis parameters. The recycling of the reflected light from the wavelength conversion element by the LED package is taken into account, as well as the re-absorption and the associated red-shift. This simulation tool is used to vary two synthesis parameters (core size and cadmium fraction) of InP/CdxZn_1-xSe quantum dots. We find general trends for the ideal quantum dot that should be combined with a specific YAG:Ce broad band phosphor to obtain optimal efficiency and color rendering for a white LED with a specific pumping LED and recycling cavity, with a desired CCT of 3500K.

Among solid-state lighting technology, phosphor-converted white light-emitting diodes (pc-WLEDs) are excellent candidates to replace incandescent lamps for their merit of high energy conservation, long lifetime, high luminous efficiency as well as polarized emissions. Semiconductor quantum dots (QDs) are emerging color tunable emissive light converters. They have shown significant promise as light emitters, as solar cells, and in biological imaging. It has been demonstrated that the pc-WLED devices integrated with red emissive ZnCdSe QDs show improved color rendering index of device. However, cadmium-based QDs have limited future owing to the well-known toxicity. Recently, non-cadmium luminescence materials, i.e. CuInS₂-based QDs, are investigated as desirable low toxic alternatives. Particularly, CuInS₂-based QDs exhibit very broad emissions spectra with full width at half maximum (FWHM) of 100-120 nm, large Stokes shifts of 200~300 meV and finely-tunable emissions. In order to adjust emission wavelengths and improved quantum yield (QY), CuInS2/ZnS (CIS/ZnS) core/shell structure was introduced. Therefore, CIS/ZnS QDs have been extensively investigated and be used as color converter in solid-state lighting. Synthesis and application of CuInS₂/ZnS core/shell QDs are conducted using a hot injection route. CIS/ZnS core/shell QDs with molar ratio of Cu:In equal to 1:4 are prepared. For WLED fabrication, the CIS/ZnS QD is dispersed in toluene first, and then it is blended with transparent acrylic-based UV resin. Subsequently, the commercial green-emitting Lu₃Al₅O₁₂: Ce³⁺ (LuAG) phosphors are mixed with QDs-resin mixture. After that, the QDs-phosphors-resin mixtures are put in the oven at 140 °C for 1 h to evaporate the toluene. Subsequently, the homogeneous QDs-phosphors-resin mixture is dropped on the top of a blue LED chip (InGaN). Then, the device is cured by 400 W UV light to form WLED. The emission wavelength of CIS/ZnS QD exhibits yellow region of 552 nm with QY of 76 %, and with relatively broad bandwidth of 86 nm. The structure of CIS/ZnS belongs to chalcopyrite phase and its average particle size is 3.2 nm. The luminous efficacy, color rendering index (CRI), correlated color temperature (CCT), and CIE chromaticity coordinate of WLED is 47 lm/W, 89, 5661 K, and (0.33, 0.29), respectively.

Recently, LED-based sources with high luminance (10⁹ cd/m² ) have been developed. These sources can be applied in projection systems, as well as in other applications requiring high luminance. The technology makes use of a transparent phosphor rod that is pumped by a multitude of blue LEDs. Most of the converted light is guided in the rod towards one of its small sides, where it is extracted using suitable extraction optics. The radiant conversion efficiency (blue flux to converted flux) is presently approaching 0.3. The causes for this limitation are discussed. The available phosphor materials emit light in various wavelength regions, ranging from green to yellow and red. These can be used in various light sources, e.g. for DLP and LCD projection.

Although the maximum brightness of LEDs has been increasing continuously during the past decade, their luminance is still far from what is required for multiple applications that still rely on the high brightness of discharge lamps. In particular for high brightness applications with limited étendue, e.g. front projection, only very modest luminance values in the beam can be achieved with LEDs compared to systems based on discharge lamps or lasers. With dedicated architectures, phosphor-converted green LEDs for projection may achieve luminance values up to 200-300 Mnit. In this paper we report on the progress made in the development of light engines based on an elongated luminescent concentrator pumped by blue LEDs. This concept has recently been introduced to the market as ColorSpark High Lumen Density LED technology. These sources outperform the maximum brightness of LEDs by multiple factors. In LED front projection, green LEDs are the main limiting factor. With our green modules, we now have achieved peak luminance values of 2 Gnit, enabling LED-based projection systems with over 4000 ANSI lm. Extension of this concept to yellow and red light sources is presented. The light source efficiency has been increased considerably, reaching 45-60 lm/W for green under practical application conditions. The module architecture, beam shaping, and performance characteristics are reviewed, as well as system aspects. The performance increase, spectral range extensions, beam-shaping flexibility, and cost reductions realized with the new module architecture enable a breakthrough in LED-based projection systems and in a wide variety of other high brightness applications.

Direct red light-emitting diodes based on InGaAlP comprise a strong temperature sensitivity regarding their output flux. In étendue-limited applications, like digital projectors, these LEDs are usually driven at current densities exceeding 3 A/mm² in pulsed mode. The losses inside the semiconductor lead to a large amount of heat, which has to be removed most efficiently by a heatsink to keep the junction temperature as low as possible and therefore to obtain the maximum output flux. One important performance parameter is the thermal resistance R_th of the LED, which has been improved during the last few years, e.g. by the development of new high-power chips and packages. In our present approach, we investigated the influence of the driving frequency – which is closely related to the thermal impedance Z_th – on the luminous and the radiant flux of red LEDs. A simulation model based on the electro-thermal analogies was implemented in SPICE and the optical and electrical characteristics of one LED type (OSRAM OSTAR Projection Power LE A P1W) were measured under application-related driving conditions while varying the parameters frequency, duty cycle, forward current, and heatsink temperature. The experimental results show clearly that the luminous and the radiant flux go up when the driving frequency is increased while the other parameters are maintained. Moreover, it can be noticed that the degree of this effect depends on the other parameters. The largest impact can be observed at the lowest tested duty cycle (30 %) and the highest tested current density (4 A/mm²) and heatsink temperature (80 °C). At this operating point, the luminous and the radiant flux increase by 20 % and 14 % respectively when raising the frequency from 240 Hz to 1920 Hz.

When designing white light systems, the use of laser diodes allows for an accurate control of the intensity pattern when combined with advanced optical components. This approach however also imposes severe challenges regarding the thermal packaging of the colour conversion element (CCE) that is used in combination with the blue laser diode(s). To correctly assess the performance of white light systems based on laser diodes, it is critical to account for the optical and thermal effects. We propose an opto-thermal design that produces white light with a very small spatial extent, approaching a point source. We optimize the system's performance with an opto-thermal simulation tool that models both the optical and thermal properties in a realistic and accurate manner. This tool allows estimating the maximum incident optical power that still results in thermally stable operation. We show that even when using high power laser diodes to excite a millimetre scale CCE, it is still possible to have a thermally stable white light system.

Scientific and technological progress of recent years in the production of the light emitting diodes (LEDs) has led to the expansion of areas of their application from the simplest systems to high precision lighting devices used in various fields of human activity. However, development and production (especially mass production) of LED lighting devices are impossible without a thorough analysis of its parameters and characteristics. There are many ways and devices for analysis the spatial, energy and colorimetric parameters of LEDs. The most methods are intended for definition only one parameter (for example, luminous flux) or one characteristic (for example, the angular distribution of energy or the spectral characteristics). Besides, devices used these methods are intended for measuring parameters in only one point or plane. This problem can be solved by using a dome diagnostics system of optical parameters and characteristics of LEDs, developed by specialists of the department OEDS chair of ITMO University in Russia. The paper presents the theoretical aspects of the analysis of LED’s spatial (angular), energy and color parameters by using mentioned of diagnostics system. The article also presents the results of spatial), energy and color parameters measurements of some LEDs brands.

Today LED headlamps, armbands and ankle-bands, shoe-lights etc. have become very popular. These find extensive use in search and rescue operations, mining, carving, etc. and are also used by individuals during hiking, trekking, running, etc. during dark hours. They serve two main purposes: they provide sufficient illumination in low light conditions and they are used to indicate the presence of a person after dark. These have the same basic requirements. They must produce sufficient light, have high durability, long battery life, must be light weight and energy efficient. This paper discusses possibilities of designing a universal LED fixture can be designed so that it meets the respective needs of everyone irrespective of their background and industry. It discusses the materials to be used for its different body parts, innovative clip design for attachment with support structures like head and armbands, helmets, shoes, etc.

This paper presents the modeling and simulation of a solar simulator that is comprised of many high-power LEDs of various wavelengths. A solar simulator is a light source which can provide optical power to measure the characteristics of solar panels indoors. For this application, the light source requires an optical spectrum and irradiance that is similar to solar rays. A high-power LED-based light source is considered to provide a light-weight design, higher luminous efficacy, and longer operating life. To match the solar spectrum, the light source in the form of an LED array needs various types of LEDs whose wavelengths and intensities are different from one another. The proposed solar simulator includes a highdensity LED fixture containing a 5 by 5 array of high-intensity LEDs. The square fixture measures 2.5 inches (63.5 mm) per side. The goal of this work is to find the radiometric power and optimum layout for an array of high-power LEDs in order to generate an optical spectrum similar to solar rays with uniform irradiance. The fixture has 18 high-power LEDs of 18 different types in the 5 by 5 array. Each LED in the fixture has a specific wavelength and intensity set by a 3D optical modeling tool. This work presents the parameters that affect spectral match and uniformity of irradiance. The parameters are the number of different LEDs used, their intensities, and arrangement. The number of LEDs and their intensities for a spectral match were computed by a developed algorithm. Modeling an LED array for spectral match, color quality, and irradiance were carried out by a 3D optical modeling tool. The results include the spectral and irradiance distributions of the proposed solar simulator.

Due to the advantages, such as high efficiency, power consumption reduction, no mercury, pure saturated color, high reliability and long lifetime, the solid-state lighting based on light-emitting diodes (LEDs) has become very popular at this stage. In the lighting applications such as spot lighting, downlighting, architectural and show lighting, the colortunable properties with collimating beam of LEDs are highly demanded. The color–tunable lighting is easily achieved using multi-colored LEDs instead of inefficient color filters. However, the applications of multi-colored LEDs usually appear the undesirable light patterns such as color separation or color fringes. At the meantime, the use of TIR (total internal reflection) lens for multi-colored LEDs to collimate the light from the LEDs with different color will introduce seriously undesirable artifacts. Thus, a periodic microstructure surface on the top surface of the TIR lens would be used to reshape the light from the different colored LED chips in the multi-colored LEDs, and then decrease the color separation and color nonuniformity. In this study, the TIR lens with periodic microstructure surface on the top surface would be used to collimate the light from multi-colored LEDs with low color separation or color fringes. The analysis of color enhancement and collimation features of the multi-colored LEDs with different periodic microstructure on the top surface of the TIR lens is presented.

Stereo depth is the most important factor for the 3D experience when viewing an autostereoscopic display. In this paper, we investigate the influence of viewing distance and viewing angle on stereo depth. First, we build the ideal stereo depth model based on the physiological limitation. Second, we establish a wave aberration model based on diffraction theory. The simulation and experimental results agree with the theoretical analyses. The model is of significant importance for giving a guidance on display system designing.

In this paper, a light box for investigation of characteristics of optoelectronic detectors is described. The light box consists of an illumination device, an optical power sensor and a mechanical enclosure. The illumination device is based on four types of high-power light emitting diodes (LED): white light, red, green and blue. The illumination level can be varied for each LED independently by the driver and is measured by optical power sensor. The mechanical enclosure provides stable mounting points for the illumination device, sensor and the examined detector and protects the system from external light, which would otherwise strongly influence the measurement results. Uniformity of illumination distribution provided by the light box for all colors is good, making the measurement results less dependent on the position of the examined detector. The response of optoelectronic detectors can be investigated using the developed light box for each LED separately or for any combination of up to four LED types. As the red, green and blue LEDs are rather narrow bandwidth sources, spectral response of different detectors can be examined for these wavelength ranges. The described light box can be used for different applications. Its primary use is in a student laboratory setup for investigation of characteristics of optoelectronic detectors. Moreover, it can also be used in various colorimetric or photographic applications. Finally, it will be used as a part of demonstrations from the fields of vision and color, performed during science fairs and outreach activities increasing awareness of optics and photonics.

Though many smart street lighting solutions is available for urban areas, comparatively fewer solutions exist for rural areas. In the recent times, village streets have been illuminated with artificial lights as a part of rural development drive undertaken by the governments of respective countries. But, vehicle and pedestrian traffic is quite low through village roads. Hence, if light remains on all night long on such roads, then there is a huge wastage of energy. This calls for solutions to reduce this energy loss in an efficient manner. There are a lot of factors which must be kept in mind while designing solutions. Many villages lack the proper infrastructure to support new technologies. Communication facilities are limited, lack of local technically skilled labor, lack of security, etc. After evaluating these opportunities and challenges, an attempt has been made to devise a smart street lighting solution tailored for remote rural areas in India. One part of the solution discusses how intensity of the LED street lights can be varied according to the ambient lighting conditions using sensors and LED switching in LED matrix. An artificial intelligence (AI) has also been modelled to identify traffic conditions using PIR sensors and object identification through image processing and independently control the lights. It also tracks the performance and status of each light. It would send this data and necessary notifications to a distant control center for human evaluation. This solution is also applicable for other rural areas throughout the world.

Using GaN-based light-emitting diodes (LEDs) as a radio source for visible light communication (VLC) is one of alternative choice in a high-speed data system. However, the spontaneous radiative recombination lifetime in the multiple quantum wells (MQWs) usually restrict the modulation bandwidth of LEDs. For LEDs accompanied photonic crystal (PhC) structure, the guided photonic modes can be extracted with a shorter radiative recombination lifetime; therefore, improve the performance of the devices for VLC. In this paper, we compare various PhC structures with corresponding dynamic behaviors in both small- and large-signal modulation. Faster transient responses and higher efficiency of the out-coupled modes were obtained in the room-temperature time-resolved photoluminescence (TRPL) and Raman scattering measurement. Here, sub-GHz modulation of GaN-based PhCLED is demonstrated, and the PhCLED exhibits a higher bandwidth than the conventional LED structure. Our study also indicates that we can not just keep scaling down the masa size of LEDs to increase the operation frequency owing to the light output power may become dull and reduce the performance of VLC system