scholarly journals Design and Performance of Nitride-based UV LEDs

2000 ◽  
Vol 622 ◽  
Author(s):  
M. H. Crawford ◽  
J. Han ◽  
R. J. Shul ◽  
M. A. Banas ◽  
J. J. Figiel ◽  
...  
Keyword(s):  
Quantum Well ◽  
High Efficiency ◽  
Active Regions ◽  
Temperature Dependent ◽  
Optical Efficiency ◽  
Uv Led ◽  
And Performance ◽  
Photoluminescence Studies ◽  
Uv Leds ◽  
Internal Absorption

ABSTRACTWe overview several of the challenges in achieving high efficiency nitride-based UV (< 400 nm) LEDs. The issue of optical efficiency is presented through temperature-dependent photoluminescence studies of various UV active regions. These studies demonstrate enhanced optical efficiencies for active regions with In-containing alloys ( InGaN, AlInGaN). We compare the performance of two distinct UV LED structures. GaN/AlGaN quantum well LEDs with λ < 360 nm emission have demonstrated output powers > 0.1 mW, but present designs suffer from internal absorption effects. InGaN/AlInGaN quantum well LEDs with 370 nm< λ < 390 nm emission and > 1 mW output power are also presented.

Optimization and performance of AlGaN-based multi-quantum-well deep-UV LEDs

2004 ◽  
Author(s):  
Mary H. Crawford ◽  
Andrew A. Allerman ◽  
Arthur J. Fischer ◽  
Katherine H. A. Bogart ◽  
Stephen R. Lee ◽  
...  
Keyword(s):  
Quantum Well ◽  
Deep Uv ◽  
And Performance ◽  
Uv Leds ◽  
Multi Quantum Well ◽  
Optimization And Performance

PROGRESS IN HIGH EFFICIENCY UV LED RESEARCH FOR REAGENTLESS BIOAGENT DETECTION AND WATER PURIFICATION

2008 ◽  
Vol 18 (01) ◽  
pp. 179-185 ◽  
Author(s):  
MEREDITH L. REED ◽  
GREGORY A. GARRETT ◽  
ANAND V. SAMPATH ◽  
PAUL H. SHEN ◽  
CHARLES J. COLLINS ◽  
...  
Keyword(s):  
Water Purification ◽  
High Efficiency ◽  
Time Resolved ◽  
Current Time ◽  
Light Emitting ◽  
Uv Led ◽  
Photoluminescence Studies ◽  
Ultraviolet Light Emitting Diodes ◽  
Time Resolved Photoluminescence

We present material and device characterization of 280 nm semiconductor ultraviolet light emitting diodes. These devices exhibit low series resistance, wavelength stability with increasing current, and have a half-life in excess of 570hrs, depending upon the injection current. Time-resolved photoluminescence studies of these materials prior to fabrication have been correlated with the device performance. We also discuss the potential for use in water purification.

scholarly journals Temperature-Dependent Luminescence of Red-Emitting Ba2Y5B5O17: Eu3+ Phosphors with Efficiencies Close to Unity for Near-UV LEDs

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 763 ◽  
Author(s):  
Egle Ezerskyte ◽  
Julija Grigorjevaite ◽  
Agne Minderyte ◽  
Sebastien Saitzek ◽  
Arturas Katelnikovas
Keyword(s):  
Optical Properties ◽  
Solid State ◽  
White Light ◽  
Light Sources ◽  
Phosphor Powder ◽  
Temperature Dependent ◽  
Blue Led ◽  
Uv Led ◽  
Uv Leds

Solid state white light sources based on a near-UV LED chip are gaining more and more attention. This is due to the increasing efficiency of near-UV-emitting LED chips and wider phosphors selection if compared to devices based on blue LED chips. Here, a brief overview is given of the concepts of generating white light employing near-UV LED and some optical properties of the available phosphors are discussed. Finally, the synthesis and optical properties of very efficient red-emitting Ba2Y5B5O17:Eu3+ phosphor powder and ceramics is reported and discussed in terms of possible application as a red component in near-UV LED-based white light sources.

Photoluminescence Studies of a Quantum Well Modulated by Faceting on Gaas (110) Surfaces

1993 ◽  
Vol 312 ◽  
Author(s):  
S. Tomiya ◽  
C. M. Reaves ◽  
M. Krishnamurthy ◽  
M. Wassermeier ◽  
D. Bimberg ◽  
...  
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Epitaxial Growth ◽  
Molecular Beam ◽  
Interface Roughness ◽  
Vicinal Surface ◽  
Temperature Dependent ◽  
Molecular Beam Epitaxial ◽  
Photoluminescence Studies ◽  
Molecular Beam Epitaxial Growth

AbstractStep bunching during epitaxial growth results in the transformation of a vicinal surface into a periodic array of micro-facets. Molecular beam epitaxial growth on the vicinal GaAs (110) surface exhibits this phenomenon which has primarily been characterized by electron microscopy. GaAs quantum wells with AlAs barriers were grown on GaAs(110) substrates vicinal 0.5-2· towards [010]. The faceting on the vicinal surface creates two distinct quantum well thicknesses. While most of the quantum well is 96Å thick, it broadens at the faceted regions. This thickness modulation produces two distinct luminescence peaks. By using temperature dependent photoluminescence, we have observed trends in exciton mobility. The exciton mobility decreases at low temperatures for the 1.0° and 2.0° samples, indicating a scattering mechanism. We will discuss interface roughness and other sources of scattering.

scholarly journals On Performance of Sparse Fast Fourier Transform Algorithms Using the Aliasing Filter

Electronics ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1117
Author(s):  
Bin Li ◽  
Zhikang Jiang ◽  
Jie Chen
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
High Efficiency ◽  
Theory And Practice ◽  
Long Time ◽  
And Performance ◽  
Binary Tree Search ◽  
The One ◽  
Sparse Fast Fourier Transform ◽  
L1 And L2

Computing the sparse fast Fourier transform (sFFT) has emerged as a critical topic for a long time because of its high efficiency and wide practicability. More than twenty different sFFT algorithms compute discrete Fourier transform (DFT) by their unique methods so far. In order to use them properly, the urgent topic of great concern is how to analyze and evaluate the performance of these algorithms in theory and practice. This paper mainly discusses the technology and performance of sFFT algorithms using the aliasing filter. In the first part, the paper introduces the three frameworks: the one-shot framework based on the compressed sensing (CS) solver, the peeling framework based on the bipartite graph and the iterative framework based on the binary tree search. Then, we obtain the conclusion of the performance of six corresponding algorithms: the sFFT-DT1.0, sFFT-DT2.0, sFFT-DT3.0, FFAST, R-FFAST, and DSFFT algorithms in theory. In the second part, we make two categories of experiments for computing the signals of different SNRs, different lengths, and different sparsities by a standard testing platform and record the run time, the percentage of the signal sampled, and the L0, L1, and L2 errors both in the exactly sparse case and the general sparse case. The results of these performance analyses are our guide to optimize these algorithms and use them selectively.

Advances in coupled axial turbine and nonaxisymmetric exhaust volute aerodynamics for turbomachinery

2020 ◽  
pp. 095441002096645
Author(s):  
Jie Gao ◽  
Chunde Tao ◽  
Dongchen Huo ◽  
Guojie Wang
Keyword(s):  
Performance Improvement ◽  
High Efficiency ◽  
Three Dimensional ◽  
Great Influence ◽  
Aerodynamic Characteristics ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Axial Turbine ◽  
Flow Interactions ◽  
And Performance

Marine, industrial, turboprop and turboshaft gas turbine engines use nonaxisymmetric exhaust volutes for flow diffusion and pressure recovery. These processes result in a three-dimensional complex turbulent flow in the exhaust volute. The flows in the axial turbine and nonaxisymmetric exhaust volute are closely coupled and inherently unsteady, and they have a great influence on the turbine and exhaust aerodynamic characteristics. Therefore, it is very necessary to carry out research on coupled axial turbine and nonaxisymmetric exhaust volute aerodynamics, so as to provide reference for the high-efficiency turbine-volute designs. This paper summarizes and analyzes the recent advances in the field of coupled axial turbine and nonaxisymmetric exhaust volute aerodynamics for turbomachinery. This review covers the following topics that are important for turbine and volute coupled designs: (1) flow and loss characteristics of nonaxisymmetric exhaust volutes, (2) flow interactions between axial turbine and nonaxisymmetric exhaust volute, (3) improvement of turbine and volute performance within spatial limitations and (4) research methods of coupled turbine and exhaust volute aerodynamics. The emphasis is placed on the turbine-volute interactions and performance improvement. We also present our own insights regarding the current research trends and the prospects for future developments.

scholarly journals Enhancing the Optical Efficiency of Near-Eye Displays with Liquid Crystal Optics

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 107
Author(s):  
Tao Zhan ◽  
En-Lin Hsiang ◽  
Kun Li ◽  
Shin-Tson Wu
Keyword(s):  
Virtual Reality ◽  
Liquid Crystal ◽  
High Efficiency ◽  
Berry Phase ◽  
Optical Element ◽  
Liquid Crystal Polymer ◽  
Proof Of Concept ◽  
Optical Efficiency ◽  
Crystal Polymer ◽  
Light Efficiency

We demonstrate a light efficient virtual reality (VR) near-eye display (NED) design based on a directional display panel and a diffractive deflection film (DDF). The DDF was essentially a high-efficiency Pancharatnam-Berry phase optical element made of liquid crystal polymer. The essence of this design is directing most of the display light into the eyebox. The proposed method is applicable for both catadioptric and dioptric VR lenses. A proof-of-concept experiment was conducted with off-the-shelf optical parts, where the light efficiency was enhanced by more than 2 times.

Sign in / Sign up

Export Citation Format

Share Document