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All sources NASA NTRS DOE OSTI

DOE OSTI2026

Mitigating Traffic Congestion Through Visual Cues: Advancing Transportation Safety and Efficiency

While humans have an innate ability to estimate speed and distance, this capability is inherently imprecise. This imprecision has significant implications for traffic systems, which are highly sensitive to fluctuations in movement. Even small variations in velocity and following distances between travelers can create congestion in high-traffic environments. The absence of an effective and widely adopted solution creates significant transportation inefficiency. However, emerging technologies offer promising ways to help mitigate this issue. This paper will analyze the effectiveness of visual cues in reducing traffic congestion. Specifically, this paper presents an experiment using addressable LEDs to evaluate their effectiveness in influencing pedestrian behavior. These programmable lights enable individual control over each LED in a strip, allowing for dynamic lighting effects that serve as useful visual cues. The goal of this paper is to demonstrate that visual cues, such as addressable LED guidance, can effectively influence traveler behavior and contribute to reducing traffic congestion.

33 ADVANCED PROPULSION SYSTEMS↗

DOE OSTI2023

Controlling the propagation asymmetry of hyperbolic shear polaritons in beta-gallium oxide

Structural anisotropy in crystals is crucial for controlling light propagation, particularly in the infrared spectral regime where optical frequencies overlap with crystalline lattice resonances, enabling light-matter coupled quasiparticles called phonon polaritons (PhPs). Exploring PhPs in anisotropic materials like hBN and MoO 3 has led to advancements in light confinement and manipulation. In a recent study, PhPs in the monoclinic crystal β-Ga 2 O 3 (bGO) were shown to exhibit strongly asymmetric propagation with a frequency dispersive optical axis. Here, using scanning near-field optical microscopy (s-SNOM), we directly image the symmetry-broken propagation of hyperbolic shear polaritons in bGO. Further, we demonstrate the control and enhancement of shear-induced propagation asymmetry by varying the incident laser orientation and polariton momentum using different sizes of nano-antennas. Finally, we observe significant rotation of the hyperbola axis by changing the frequency of incident light. Our findings lay the groundwork for the widespread utilization and implementation of polaritons in low-symmetry crystals.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Origin of reduced efficiency in GaN-based micro-LEDs studied by scanning near-field optical microscopy

The quantum efficiency of micro-light emitting diodes (micro-LEDs) is lower than that of large area LEDs. This efficiency reduction is typically attributed to the nonradiative Shockley–Read–Hall recombination at the surface defects and current leakage through the sidewall region without a clear distinction between these effects. In this work, we attempt to find out which of these phenomena is most critical for the reduced efficiency of micro-LEDs. This has been done by mapping electroluminescence (EL) and photoluminescence (PL) and measuring PL dynamics in blue GaN micro-LEDs fabricated by dry etching. It has been found that in the as-etched device, the EL intensity is much lower than in devices with KOH etching and atomic layer deposition of SiO 2 . This effect is especially pronounced close to the sidewalls. On the other hand, PL decay times are similar in as-etched and passivated devices, both in their center and at the sidewalls. This allows concluding that the main mechanism of the reduced efficiency of micro-LEDs fabricated by dry etching is the current leakage in the sidewall region and not the nonradiative recombination. The KOH etching has been found to be the most efficient means to eliminate the current leakage.

36 MATERIALS SCIENCE↗

NASA NTRS1976

Digital time slot display for Omega receiver

Methods of decoding a digital word to display alpha-numeric characters for driving a standard seven-segment LED display have been devised for Omega station identification. The circuit could replace the system now being used in Ohio University's Omega receivers, which lights one of eight LED's to signify the Omega time slot being received. The letters A through H, representing the Omega stations, can be read directly from the seven-segment display.

Smith, R. E.↗

DOE OSTI2025

Dual interfacial H-bonding-enhanced deep-blue hybrid copper–iodide LEDs

Solution-processed light-emitting diodes based on non-toxic copper–iodide hybrids are a compelling solution for efficient and stable deep-blue lighting, owing to their tunability, high photoluminescence efficiency and environmental sustainability. Here we present a hybrid copper–iodide that shows near-unity photoluminescence quantum yield (99.6%) with an emission wavelength of 449 nm and colour coordinates (0.147, 0.087), alongside its emission mechanism and charge transport characteristics. Here, we use the thin film of this hybrid as the sole active emissive layer to fabricate deep-blue light-emitting diodes and subsequently enhance the device performance through a dual interfacial hydrogen-bond passivation strategy. This synergetic surface modification approach, integrating a hydrogen-bond-acceptor self-assembled monolayer with an ultrathin polymethyl methacrylate capping layer, effectively passivates both heterojunctions of the copper–iodide hybrid emissive layer and optimizes charge injections. We achieve a maximum external quantum efficiency of 12.57%, a maximum luminance of 3,970.30 cd m −2 with colour coordinates (0.147, 0.091) and an excellent operational stability (half-lifetime) of 204 hours under ambient conditions. We further showcase a large-area device of 4 cm 2 that maintains high efficiency. Our findings reveal the potential of copper–iodide-based hybrid materials for applications in solid-state lighting and display technologies, offering a versatile strategy for enhancing device performances.

14 SOLAR ENERGY↗

NASA NTRS2014

UV-LED Project

UV-LED is part of a small satellite technologydemonstration mission that willdemonstrate non-contacting charge controlof an isolated or floating mass usingnew solid-state ultra-violet light emittingdiodes (UV-LEDs). Integrated tothe Saudisat-4 spacecraft and launchedonboard the Dnepr in June 19, 2014,the project is a collaboration betweenthe NASA Ames Research Center (ARC),Stanford University, and King AbdulazizCity for Science and Technology(KACST). This technology demonstrationwill validate a novel method of chargecontrol that will improve the performanceof drag-free spacecraft allowingfor concurrent science collection duringcharge management operations as wellas reduce the mass, power and volumerequired while increasing lifetime and reliabilityof a charge management subsystem.These improvements are crucial tothe success of ground breaking missionssuch as LISA and BBO, and demonstratethe ability of low cost small satellite missionsto provide technological advancesthat far exceed mission cost.

Soulage, Michael↗

DOE OSTI2021

Hybrid chip-on-board LED module with patterned encapsulation

Light modules and methods of forming light modules are disclosed. A light module includes a first plurality and a second plurality of light emitting elements configured to emit, respectively, a first light and a second light, and both arranged on a substrate. An encapsulation layer is disposed over the first and second plurality of the light emitting elements, and a wavelength converting element is dispersed in the encapsulation layer. A concentration of the wavelength converting element in the encapsulation layer varies, is larger over the first plurality of light emitting elements and is smaller over the second plurality of light emitting elements.

Soer, Wouter Anthon↗

DOE OSTI2020

Adoption of Light-Emitting Diodes in Common Lighting Applications

The 2020 edition of a report which models the current state of the U.S. general-lighting market and provides analysis on realized and potential energy- and money-saving benefits associated with LED lamps and luminaires.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

NASA NTRS2014

Microorganisms in the Stratosphere (MIST): In-flight Sterilization with UVC Leds

The stratosphere (10 km to 50 km above sea level) is a unique place on Earth for astrobiological studies of microbes in extreme environments due to the combination of harsh conditions (high ultraviolet radiation, low pressure, desiccation, and low temperatures). Microorganisms in the Stratosphere (MIST) will attempt to characterize the diversity of microbes at these altitudes using a balloon collection device on a meteorological weather balloon. A major challenge of such an aerobiology study is the potential for ground contamination that makes it difficult to distinguish between collected microbes and contaminants. One solution is to use germicidal ultraviolet light emitting diodes (UV LEDs) to sterilize the collection strip. To use this solution, an optimal spatial arrangement of the lights had to be determined to ensure the greatest chance of complete sterilization within the 30 to 60 minute time of balloon ascent. A novel, 3D-printed test stand was developed to experimentally determine viable Bacillus pumilus SAFR-032 spore reduction after exposure to ultraviolet radiation at various times, angles, and distances. Taken together, the experimental simulations suggested that the UV LEDs on the MIST flight hardware should be active for at least 15 minutes and mounted within 4 cm of the illuminated surface at any angle to achieve optimal sterilization. These findings will aid in the production of the balloon collection device to ensure pristine stratospheric microbial samples are collected. Flight hardware capable of in-flight self-sterilization will enable future life detection missions to minimize both forward contamination and false positives.

Exobiology↗

DOE OSTI2020

Probing light-driven quantum materials with ultrafast resonant inelastic X-ray scattering

Abstract Ultrafast optical pulses are an increasingly important tool for controlling quantum materials and triggering novel photo-induced phase transitions. Understanding these dynamic phenomena requires a probe sensitive to spin, charge, and orbital degrees of freedom. Time-resolved resonant inelastic X-ray scattering (trRIXS) is an emerging spectroscopic method, which responds to this need by providing unprecedented access to the finite-momentum fluctuation spectrum of photoexcited solids. In this Perspective, we briefly review state-of-the-art trRIXS experiments on condensed matter systems, as well as recent theoretical advances. We then describe future research opportunities in the context of light control of quantum matter.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

NASA NTRS1994

Light emitting diodes as a plant lighting source

Electroluminescence in solid materials is defined as the generation of light by the passage of an electric current through a body of solid material under an applied electric field. A specific type of electroluminescence, first noted in 1923, involves the generation of photons when electrons are passed through a p-n junction of certain solid materials (junction of a n-type semiconductor, an electron donor, and a p-type semiconductor, an electron acceptor). The development of this light emitting semiconductor technology dates back less than 30 years. During this period of time, the LED has evolved from a rare and expensive light generating device to one of the most widely used electronic components. A number of LED characteristics are of considerable importance in selecting a light source for plant lighting in a controlled environment facility. Of particular importance is the characteristic that light is generated by an LED at a rate far greater than the corresponding thermal radiation predicted by the bulk temperature of the device as defined by Plank's radiation law. This is in sharp contrast to other light sources, such as an incandescent or high intensity discharge lamp. A plant lighting system for controlled environments must provide plants with an adequate flux of photosynthetically active radiation, plus providing photons in the spectral regions that are involved in the photomorphogenic and phototropic responses that result in normal plant growth and development. Use of light sources that emit photons over a broad spectral range generally meet these two lighting requirements. Since the LED's emit over specific spectral regions, they must be carefully selected so that the levels of photsynthetically active and photomorphogenic and phototropic radiation meet these plant requirements.

Bula, R. J.↗

NASA NTRS2011

Growth of Three Lettuce Cultivars in NASA's HDU PEM During the 2010 DRATS Test

NASA's 2010 Desert Research and Technology Studies (DRATS) of the VEGGIE Food Production System in the Habitat Demonstration Unit (HDU) Pressurized Excursion Module (PEM) was the first operational evaluation of salad crop production technology in a NASA analog test. Rooting media and slow release fertilizers were evaluated for three lettuce cultivars that had shown promise as candidates for a surface based food production system. These tests involved comparing growth, color and quality of the lettuce cultivars grown under VEGGIE LED array (Orbitec, Madison, WI) or Biomass Production System for Education ((BSEe), Orbitec, Madison, WI) compact fluorescent lamps using a gravity feed water delivery system. Mission relevant conditions of CO2, temperature and RH were maintained using controlled environment chambers (EGC, Chagrin Falls, OH). Growth data was obtained for the two red leaf lettuce cultivars, Outredgeous and Firecracker, and the green Bibb lettuce cultivar, Flandria. Growth and quality was evaluated using different concentrations (7.5 g/L and 15 g/L) of commercial slow release fertilizer (Osmocote Plus 15-9-12, Scotts, Maryville, OH) and Nutricote 18-6-8 (Florikan, Sarasota, FL) in either a peat/vermiculite media (sunshine LP5 MiX, Sungro, Bellview, WA) or calcined montmorillonite clay [(arcillite,)Turface Proleague, Profile LLC, Buffalo Grove, IL]. The commercial peat/vermiculite mix generally resulted in larger plants than those grown in arcillite. Increasing the concentration of Osmocote from 7.5 to 15 g/L increased the height, dry mass, and leaf area of lettuce cultivars. In contrast, there was a decrease in growth parameters when concentration of Nutricote was increased from 7.5 to 15 g/L. The best growth was obtained with the 7.5 g/L Nutricote using a commercial peat/vermiculite mixture. This media was used for field testing VEGGIE plant system in the 2010 DRAT test. The VEGGIE nutrient delivery system worked well, was able to be maintained by multiple operators with a minimum of training, and supported excellent lettuce growth for the duration of the 14-day test. The operational DRAT field testing in the HDU identified light quality issues related to morphology and pigment development that will need to be addressed through additional testing. Feedback from the crew, ground support personnel, and human factors leads was uniformly positive on the psychological value of having the crop production system in the pressurized excursion module. Data are being used to design a plant atrium with LED lighting to evaluate salad crop growth during NASA's 2011 DRATS test.

Stutte, Gary W.↗

DOE OSTI2024

2020 U.S. Lighting Market Characterization

The Lighting Market Characterization report details how many lighting products (lamps and luminaires) were installed in the U.S. as of 2020, where they were installed, and how much energy they consumed. It also highlights key changes in U.S. lighting market characteristics between 2015 and 2020. This is the fourth edition of the LMC report; previous versions were released in 2002, 2012 and 2017. By publishing summary estimates of installed stock and energy use of various general illumination lighting products, these reports help DOE and others plan effective lighting research and development programs based on changing needs.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2024

2020 U.S. Lighting Market Characterization

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2022

Impact of Solid State Roadway Lighting on Melatonin in Humans

Introduction: In 2009, the World Health Organization identified vehicle crashes, both injury-related and fatal, as a public health hazard. Roadway lighting has long been used to reduce crashes and improve the safety of all road users. Ocular light exposure at night can suppress melatonin levels in humans. At sufficient light levels, all visible light wavelengths can elicit this response, but melatonin suppression is maximally sensitive to visible short wavelength light. With the conversion of roadway lighting to solid state sources that have a greater short wavelength spectrum than traditional sources, there is a potential negative health impact through suppressed melatonin levels to roadway users and those living close to the roadway. This paper presents data on the impact of outdoor roadway lighting on salivary melatonin in three cohorts of participants: drivers, pedestrians, and those experiencing light trespass in their homes. Methods: In an outdoor naturalistic roadway environment, healthy participants (N = 29) each being assigned to a cohort of either pedestrian, driver, or light trespass experiment, were exposed to five different solid state light sources with differing spectral emissions and one no lighting condition. Salivary melatonin measurements were made under an average roadway luminance of 1.0 cd/m2 (IES RP-18 Roadway Lighting Requirements for expressway roads) with a corneal melanopic Equivalent Daylight Illuminances (EDI) ranging from 0.22 to 0.86 lux. Results: The results indicate that compared to the no roadway lighting condition, the roadway light source spectral content did not significantly impact salivary melatonin levels in the participants in any of the cohorts. Conclusions: These data show that recommended levels of street lighting for expressway roads do not elicit an acute suppression of salivary melatonin and suggest that the health benefit of roadway lighting for traffic safety is not compromised by an acute effect on salivary melatonin.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2024

2020 U.S. Lighting Market Characterization

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

NASA NTRS2015

NASA Ames UV-LED Poster Overview

UV-LED is a small satellite technology demonstration payload being flown on the Saudisat-4 spacecraft that is demonstrating non-contacting charge control of an isolated or floating mass using new solid-state ultra-violet light emitting diodes (UV-LEDs). Integrated to the rest of the spacecraft and launched on a Dnepr in June 19, 2014, the project is a collaboration between the NASA Ames Research Center (ARC), Stanford University, and King Abdulaziz City for Science and Technology (KACST). Beginning with its commissioning in December, 2015, the data collected by UV-LED have validated a novel method of charge control that will improve the performance of drag-free spacecraft allowing for concurrent science collection during charge management operations as well as reduce the mass, power and volume required while increasing lifetime and reliability of a charge management subsystem. UV-LED continues to operate, exploring new concepts in non-contacting charge control and collecting data crucial to understanding the lifetime of ultra-violet light emitting diodes in space. These improvements are crucial to the success of ground breaking missions such as LISA and BBO, and demonstrates the ability of low cost small satellite missions to provide technological advances that far exceed mission costs.

KACST↗

DOE OSTI2022

Lighting: Development, Adoption, and Compliance Guide

The guide provides information for anyone dealing with a lighting energy code or standard. It provides background and development information to help readers understand the basis for requirements and their intent. The guide also provides detailed explanations of the major types of requirements such that users can more effectively design to meet compliance while applying the most flexibility possible.

Luminaires, IECC, code compliance, high-intensity ↗