Surface patterning of nonscattering phosphors for light extraction

Mao, An; Karlicek, R. F.

doi:10.1364/ol.38.002796

Cited by 27 publications

(15 citation statements)

References 12 publications

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“…For example, the architecture of “YAG:Ce film + sapphire substrate” yields a high light conversion efficiency of 256 lm W −1 , and can withstand a blue laser power density up to 11.2 W mm −2 . Moreover, the surface of the sapphire substrate can be coated with 1D photonic crystals (1DPCs) to improve the light extraction efficiency . With regard to quantum‐well LED, its application for laser lighting is still limited by the rather low quantum efficiency.…”

Section: Discussionmentioning

confidence: 99%

“…Different from white LEDs, strong scattering is a requisite to improve the light extraction efficiency and to solve the “yellow‐ring” problem in laser lighting in consideration of the highly directional and focused incident light source . Some methods, such as bulk scattering designing, surface roughening, and photonic crystal layer coating, should be investigated/developed to prevent the light escape through total internal refraction or trapping . On the other hand, some heating effects (e.g., more heat generation and weakened heat transfer) definitely occur in the high‐scattering color converters.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Color Conversion Materials for High‐Brightness Laser‐Driven Solid‐State Lighting

Wang

Hirosaki

et al. 2018

Laser & Photonics Reviews

273

191

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Solid‐state lighting is advancing toward higher power, higher brightness, and smaller size to cope with the market competitiveness, and laser‐driven solid‐state lighting technology is springing up owing to its super‐high brightness and compactness. These developments put forward new requirements for color conversion materials (i.e., phosphors). Here, the state‐of‐art achievements in laser phosphors are summarized, and the topics of luminescence saturation, light extraction efficiency, and light uniformity encountered in laser lighting technology are discussed. Several typical types of color converters, such as single crystal, phosphor ceramics, phosphor‐in‐glass, phosphor films, and quantum‐well light‐emitting diodes, are comparatively overviewed and discussed. The cutting‐edge applications of high‐brightness white laser light in lighting, displays, healthcare, and communications are summarized. The challenges and outlook in laser‐driven solid‐state lighting and some empirical rules for designing novel laser phosphors are highlighted.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Color Conversion Materials for High‐Brightness Laser‐Driven Solid‐State Lighting

Wang

Hirosaki

et al. 2018

Laser & Photonics Reviews

273

191

View full text Add to dashboard Cite

show abstract

“…However, the high refractive index of crystalline materials causes a quite small critical angel and thus strong total internal reflection (TIR), seriously deteriorating the light extraction efficiency. [38][39][40][41] To solve this problem, light scattering centers must be introduced. Recently, the YAG:Ce-Al 2 O 3 composite ceramic has been proposed for use in laser lighting because of its: i) high thermal conductivity and ii) high luminous efficacy caused by the scattering of secondary Al 2 O 3 grains.…”

Section: Doi: 101002/lpor201900147mentioning

confidence: 99%

Unique Design Strategy for Laser‐Driven Color Converters Enabling Superhigh‐Luminance and High‐Directionality White Light

Zheng

Wei

et al. 2019

Laser & Photonics Reviews

113

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Robust ceramic color converters withstanding strong laser irradiations have recently drawn great attention for laser‐driven white lighting. However, the local emission within the incident laser spot usually expands to the whole surface area of the ceramics, which definitely makes it hard to achieve white light with high luminance and high directionality. Herein, a new strategy is proposed to solve the problem by elaborately introducing uniform spherical pores (diameter of ≈2 µm) into the phosphor ceramics with controlled contents from 8 to 24.6 vol%. The well‐distributed pores, acting as light scattering centers, enable reduction of the luminescent spot size greatly but without any losses in conversion efficiency. By using the high‐scattering ceramic color converters with 15% porosity, the light spot diameter is decreased by 46% and the central illuminance is increased by 156%. Moreover, laser‐driven white light with an enhanced beam directionality and uniformity is also achieved. A superhigh luminous flux of 7199 lm is realized by using this promising color converter in a rotary mode. The designed high‐scattering ceramics with controllable microstructures show great potential for use in extra‐high luminance laser‐driven lighting and projection.

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“…Therefore, depositing a thin film of another material on the YAG:Ce 3+ surface, offers a good alternative. SiO 2 , TiO 2 , and Si 3 N 4 are popular photonic bandgap materials used in the formation of PCLs on phosphor plates [181][182][183][184][185][186] and they can be deposited on a large scale with relatively low-cost processes. In particular, the high transparency at visible wavelengths and the relatively large refractive index (~2.4) of TiO 2 makes it a favorable material for making PCLs on YAG:Ce 3+ ceramic converters.…”

Section: White Ledsmentioning

confidence: 99%

Optoelectronic device physics and technology of nitride semiconductors from the UV to the terahertz

2017

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This paper reviews the device physics and technology of optoelectronic devices based on semiconductors of the GaN family, operating in the spectral regions from deep UV to Terahertz. Such devices include LEDs, lasers, detectors, electroabsorption modulators and devices based on intersubband transitions in AlGaN quantum wells (QWs). After a brief history of the development of the field, we describe how the unique crystal structure, chemical bonding, and resulting spontaneous and piezoelectric polarizations in heterostructures affect the design, fabrication and performance of devices based on these materials. The heteroepitaxial growth and the formation and role of extended defects are addressed. The role of the chemical bonding in the formation of metallic contacts to this class of materials is also addressed. A detailed discussion is then presented on potential origins of the high performance of blue LEDs and poorer performance of green LEDs (green gap), as well as of the efficiency reduction of both blue and green LEDs at high injection current (efficiency droop). The relatively poor performance of deep-UV LEDs based on AlGaN alloys and methods to address the materials issues responsible are similarly addressed. Other devices whose state-of-the-art performance and materials-related issues are reviewed include violet-blue lasers, 'visible blind' and 'solar blind' detectors based on photoconductive and photovoltaic designs, and electroabsorption modulators based on bulk GaN or GaN/AlGaN QWs. Finally, we describe the basic physics of intersubband transitions in AlGaN QWs, and their applications to near-infrared and terahertz devices.

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Surface patterning of nonscattering phosphors for light extraction

Cited by 27 publications

References 12 publications

Color Conversion Materials for High‐Brightness Laser‐Driven Solid‐State Lighting

Color Conversion Materials for High‐Brightness Laser‐Driven Solid‐State Lighting

Unique Design Strategy for Laser‐Driven Color Converters Enabling Superhigh‐Luminance and High‐Directionality White Light

Optoelectronic device physics and technology of nitride semiconductors from the UV to the terahertz

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