Beveled sidewall formation and its effect on the light output of a GaInN multiquantum well light-emitting diode with sapphire substrate

2005 ◽  
Vol 44 (11) ◽  
pp. 111304 ◽  
Author(s):  
Jung-Tsung Hsu
Keyword(s):  
Sapphire Substrate ◽  
Light Emitting Diode ◽  
Light Output ◽  
Light Emitting ◽  
Multiquantum Well

scholarly journals A 3 W High-Voltage Single-Chip Green Light-Emitting Diode with Multiple-Cells Network

2015 ◽  
Vol 2015 ◽  
pp. 1-4 ◽  
Author(s):  
W. Wang ◽  
Y. Cai ◽  
Y. B. Zhang ◽  
H. J. Huang ◽  
W. Huang ◽  
...  
Keyword(s):  
High Voltage ◽  
Light Emitting Diode ◽  
Light Output ◽  
Green Light ◽  
Current Crowding ◽  
Single Chip ◽  
Light Output Power ◽  
Large Area ◽  
Light Emitting ◽  
Multiple Cells

A parallel and series network structure was introduced into the design of the high-voltage single-chip (HV-SC) light-emitting diode to inhibit the effect of current crowding and to improve the yield. Using such a design, a6.6×5 mm2large area LED chip of 24 parallel stages was demonstrated with 3 W light output power (LOP) at the current of 500 mA. The forward voltage was measured to be 83 V with the same current injection, corresponding to 3.5 V for a single stage. The LED chip’s average thermal resistance was identified to be 0.28 K/W by using infrared thermography analysis.

Enhanced Emission from a Light-Emitting Diode Modified by a Photonic Crystal

2000 ◽  
Vol 637 ◽  
Author(s):  
Alexei A. Erchak ◽  
Daniel J. Ripin ◽  
Shanhui Fan ◽  
John D. Joannopoulos ◽  
Erich P. Ippen ◽  
...  
Keyword(s):  
Photonic Crystal ◽  
Planar Waveguide ◽  
Optical Pumping ◽  
Extraction Efficiency ◽  
Light Emitting Diode ◽  
Active Material ◽  
Light Output ◽  
Vertical Direction ◽  
Light Emitting ◽  
Spectrally Resolved

AbstractEnhanced light output is observed from a light-emitting diode (LED) structure containing a two-dimensional (2D) photonic crystal. The capture of emitted light into planar waveguide modes reduces the extraction efficiency of LEDs. Here, 2D photonic crystals are utilized to: 1) enhance the extraction of light in the vertical direction from an LED and 2) enhance optical pumping by directly coupling light from a pump laser into the LED structure. Spatially and spectrally-resolved photoluminescence (PL) is used to characterize the enhancements. A 100-fold enhancement in extraction for a single wavelength into the vertical direction is obtained without the photonic crystal penetrating the active material.

scholarly journals Emission Characteristics and Effect of Battery Drain in “Budget” Curing Lights

2016 ◽  
Vol 41 (4) ◽  
pp. 397-408 ◽  
Author(s):  
MM AlShaafi ◽  
JE Harlow ◽  
HL Price ◽  
FA Rueggeberg ◽  
D Labrie ◽  
...  
Keyword(s):  
Light Emitting Diode ◽  
Medical Instrument ◽  
Light Output ◽  
The Internet ◽  
Spectral Emission ◽  
Light Emitting ◽  
Power Spectral ◽  
Radiant Power ◽  
And Performance ◽  
Emission Ratios

SUMMARY Recently, “budget” dental light-emitting diode (LED)–based light-curing units (LCUs) have become available over the Internet. These LCUs claim equal features and performance compared to LCUs from major manufacturers, but at a lower cost. This study examined radiant power, spectral emission, beam irradiance profiles, effective emission ratios, and the ability of LCUs to provide sustained output values during the lifetime of a single, fully charged battery. Three examples of each budget LCU were purchased over the Internet (KY-L029A and KY-L036A, Foshan Keyuan Medical Equipment Co, and the Woodpecker LED.B, Guilin Woodpecker Medical Instrument Co). Major dental manufacturers provided three models: Elipar S10 and Paradigm (3M ESPE) and the Bluephase G2 (Ivoclar Vivadent). Radiant power emissions were measured using a laboratory-grade thermopile system, and the spectral emission was captured using a spectroradiometer system. Irradiance profiles at the tip end were measured using a modified laser beam profiler, and the proportion of optical tip area that delivered in excess of 400 mW/cm2 (termed the effective emission ratio) was displayed using calibrated beam profile images. Emitted power was monitored over sequential exposures from each LCU starting at a fully charged battery state. The results indicated that there was less than a 100-mW/cm2 difference between manufacturer-stated average tip end irradiance and the measured output. All the budget lights had smaller optical tip areas, and two demonstrated lower effective emission ratios than did the units from the major manufacturers. The budget lights showed discontinuous values of irradiance over their tip ends. One unit delivered extremely high output levels near the center of the light tip. Two of the budget lights were unable to maintain sustained and stable light output as the battery charge decreased with use, whereas those lights from the major manufacturers all provided a sustained light output for at least 100 exposures as well as visual and audible indications that the units required recharging.

Modeling and Analysis of Organic Light Emitting Diode with Thin Film Anti-Reflective Coatings

2020 ◽  
Vol 15 (4) ◽  
pp. 425-431
Author(s):  
B. M. Chaya ◽  
Prasant Kumar Pattnaik ◽  
K. Narayan
Keyword(s):  
Power Efficiency ◽  
Light Emitting Diode ◽  
Fdtd Method ◽  
Light Output ◽  
Single Layer ◽  
Light Emitting ◽  
Organic Light Emitting Diode ◽  
Reflective Coating ◽  
Organic Light ◽  
Reflective Coatings

The effects of anti-reflective coatings (ARC) on organic light emitting diode (OLED) optical characteristics are reported in this paper. The light output produced from the OLED is not 100%. But the emitted light is trapped due to various Modes. The losses at the glass air substrate interfaces of an OLED are addressed in this work. The Anti-Reflective coatings increase the light output by reducing OLED reflections at the interface between glass and air. The Finite Difference Time Domain (FDTD) method and the Fresnel theory have been used to design the device and study the effects on OLED of the Single Layer Anti-Reflective Coating (SLAR) and Double Layer Anti-Reflective Coating (DLAR). The thicknesses and refractive indices of the layers of the anti-reflective coatings were optimized. We also compared the light out coupling power efficiency of the SLAR coated OLED with that of an OLED with a DLAR coating and also with Conventional OLED. The results show that the enhancement in light output efficiency of the DLAR coated OLED was slightly higher than that of the SLAR coated OLED.

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