Polarized light emission from photonic crystal light-emitting diodes

Lai, Chun‐Feng; Yong, Jim; Yen, Hsi Hsuan; Kuo, Hao‐Chung; Chao, Chia-Hsin; Hsueh, H. T.; Wang, Jih Fu Trevor; Huang, Cheng‐Liang; Yeh, Wen-Yung

doi:10.1063/1.2938885

Cited by 43 publications

(24 citation statements)

References 12 publications

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“…It is found that the PhC can behave as a polarizer to improve the P/S ratio of the extracted EL emission. The results of the P/S ratio for light propagating in different lattice orientation was found to be consistent with the results obtained using the PhC Bloch mode coupling theory [10,[27][28].…”

Section: Polarized Light Emission Properties Of Gan-based Photonic Crsupporting

confidence: 76%

Anisotropy of Light Extraction Emission with High Polarization Ratio from GaN-based Photonic Crystal Light-Emitting Diodes

Lai¹,

Chao²,

Kuo³

2010

Recent Optical and Photonic Technologies

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Section: Polarized Light Emission Properties Of Gan-based Photonic Crsupporting

confidence: 76%

Anisotropy of Light Extraction Emission with High Polarization Ratio from GaN-based Photonic Crystal Light-Emitting Diodes

Lai¹,

Chao²,

Kuo³

2010

Recent Optical and Photonic Technologies

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“…The original polarization of the direct light and guided modes is not disturbed, neither by the LED structure, nor by the PhCs, since their different interfaces are parallel to each other, as well as to the direction of the main electric fieldẼ Ejjã a, denoted by E a (see Supplementary Information). 28,29 Figure 4a shows the electric field profile of three of the guided modes supported in the thin waveguide diffracted by the PhCs. The diffracted in-plane wave vectors are conserved in different media, and different guided modes are diffracted by the PhCs at different well defined angles.…”

Section: Photonic-crystal Design Rulesmentioning

confidence: 99%

High-brightness polarized light-emitting diodes

et al. 2012

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Light-emitting diodes are becoming the alternative for future general lighting applications, with huge energy savings compared to conventional light sources owing to their high efficiency and reliability. Polarized light sources would largely enhance the efficiency in a number of applications, such as in liquid-crystal displays, and also greatly improve contrast in general illumination due to the reduction in indirect glare. Here, we demonstrate light-emitting diodes presenting high-brightness polarized light emission by combining the polarization-preserving and directional extraction properties of embedded photonic-crystals applied to non-polar gallium nitride. A directional enhancement of up to 1.8-fold was observed in the total polarized light emission together with a high polarization degree of 88.7% at 465 nm. We discuss the mechanisms of polarized light emission in non-polar gallium nitride and the photonic-crystal design rules to further increase the light-emitting diode brightness. This work could open the way to polarized white-light emitters through their association with polarization-preserving down-converting phosphors. INTRODUCTIONDue to a continuously improved performance, light-emitting diodes (LEDs) are not only the major contender for future general lighting sources, 1 but also play an important role in a growing number of other applications-from backlight for high-efficiency televisions and mobile phone displays, to car lights and headlights-replacing the classical white sources owing to their high efficiency, brightness, reliability and low operation cost. Polarized light sources would largely improve the efficiency of most of these applications: from general illumination, with an improved contrast due to reduced glare, 2 which also minimizes eye discomfort and ultimately eye strain, 3 to highefficiency displays which operate through the spatial modulation of polarized light 4 (for completeness, we also note that polarized light and other forms of artificial light could be harmful for the life of animals and other species relying on natural light cycles to live 5 ). However, common light sources are usually unpolarized, since the electric field of the light emitted has no preferred orientation. This is also the case for most of the nitride-based LEDs commercialized nowadays. A strongly linearly polarized source, however, is obtained in m-plane GaN LEDs where the asymmetric in-plane biaxial stress on the quantum wells (QWs) orients the light emitting dipoles preferentially along the in-plane a direction. Non-polar m-plane GaN LEDs were first developed and more intensively investigated due to the possible reduction of polarization-induced electric fields in the QWs, which for c-plane GaN LEDs degrade their radiative recombination rate as a result of quantum confined stark effects. 6,7 Today, the

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“…We investigated the square lattice because it is simple, retains the 2-D features, and is a model system for other slab structures. It is also the lattice structure that favors the polarized light emission [5]. The angular-resolved spectroscopic technique is a powerful method to investigate the quasiresonant modes that lie above the light lines to extract the waveguided lights.…”

Section: Resultsmentioning

confidence: 99%

“…Aperiodic PhC patterns have been reported for isotropic light extraction [6]. For controlling the collimation and polarization properties, periodic PhC with anisotropic light extraction has also been reported [4], [5], [8]. In this study, a detailed investigation was conducted to gain insights for the nearfield and the far-field distribution of the guided mode extraction from the GaN-based PhC LEDs under electrical injection.…”

Section: Introductionmentioning

confidence: 99%

Far-Field and Near-Field Distribution of GaN-Based Photonic Crystal LEDs With Guided Mode Extraction

Lai

Chi

Kuo

et al. 2009

IEEE J. Select. Topics Quantum Electron.

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Abstract-The near-field and far-field distribution of GaN LEDs with square photonic crystal (PhC) lattice are experimentally investigated. The optical images of the near-field pattern are obtained from the guided electroluminescent light generated at the center of a special annular structure. For increasing lattice constant, symmetric patterns with varying number of petals according to the symmetry of the PhC are observed. The far-field distribution is studied with GaN-based film-transferred PhC LEDs with the thickness about 1500 nm. Angular-resolved measurements under electrical injection revealed guided modes extraction behavior and polarization based on the Bragg's diffraction with the PhC lattice. Good agreement with the two-dimension free photon band structure is obtained.

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Polarized light emission from photonic crystal light-emitting diodes

Cited by 43 publications

References 12 publications

Anisotropy of Light Extraction Emission with High Polarization Ratio from GaN-based Photonic Crystal Light-Emitting Diodes

Anisotropy of Light Extraction Emission with High Polarization Ratio from GaN-based Photonic Crystal Light-Emitting Diodes

High-brightness polarized light-emitting diodes

Far-Field and Near-Field Distribution of GaN-Based Photonic Crystal LEDs With Guided Mode Extraction

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