Laser Diode Induced Lighting Modules

Abstract

Laser diodes have the potential of becoming the light engines of future lighting technology since they have negligible efficiency droop factor, unlike light emitting diodes. This study demonstrates the possibility of laser diodes coupled to phosphor targets being used as a solid state lighting system with high power applications. It was revealed that white light emitting modules with efficiency of up to 217 lumens per watt based on laser diodes can currently be made and upon further development of laser diode technology and relevant phosphor materials there is room for further improvements. The report also demonstrates the ability of this technology to produce a tailored emission spectrum for a given specific requirement. Two test lamp prototypes were made using laser diodes and phosphor targets and their emission characteristics were investigated. © The Author(s) 2016. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. [DOI: 10.1149/2.0101603jss] All rights reserved. Currently light emitting diodes (LEDs) coupled with phosphors are the most efficient source of solid state white light provided that they are operated at low input powers. The drop in the LED's efficiency at higher input powers is associated to a phenomenon called the efficiency droop. This phenomenon has been investigated for the past decade and is thought to be linked to the Auger effect.1-3 Despite extensive research in to the field no fundamental or definitive solution has been put forward to eliminate this effect. To achieve more lumens per power consumed, the LEDs are typically operated under higher input powers at the expense of efficiency.An alternative approach is to use Laser Diodes (LDs) in combination with the same phosphors applied in LED lighting but packaged differently to achieve high performance and efficient solid state lighting (SSL). The LDs are operated under stimulated emission and the mechanisms of efficiency droop are clamped at their lasing threshold. 4 This concludes that through application of LDs, higher efficiencies at higher input power densities can be achieved. The LDs are more efficient in this respect because they are operated by stimulated emission. At lasing threshold, all the recombination processes (The Auger, Shockley-Read-Hall mechanism & spontaneous) are clamped and additional carriers injected into the light quantum wells contribute only to stimulated emission, so it can be argued that unless a fix to the efficiency droop which is an intrinsic issue is found, the LDs will be competing with LEDs for the future of high brightness/high power SSL modules.5 Figure 1 demonstrates a comparison of the power conversion efficiency (PCE) of LDs and LEDs and what is expected in terms of performance improvement from them in future. Future LEDs will require modules which have a shift in PCE ...

Composition and luminescence properties of highly robust green-emitting LuAG:Ce/Al 2O 3 composite phosphor ceramics for high-power solid-state lighting

“…As we all know, the operating temperature of core devices in high-power white LEDs/LDs can reach up to 200 ℃, which places high demands on the thermal performance of color converter [7][8][9][10]. Currently, the main phosphor converters used in commercial white LEDs are manufactured by mixing YAG:Ce phosphor powders and silicone resins [11,12].…”

ZnCdS:Cu,Al,Cl: A Near Infra-Red Emissive Family of Phosphors for Marking, Coding, and Identification

“…Device fabrication and testing.-Recently we have carried out studies using blue laser diodes to assess the performance of phosphor screen and yttrium aluminum garnet crystals doped with cerium. [37][38][39] To test the possible application of the phosphors for marking at night a sample of Zn 0.4 Cd 0.6 S:Cu 0.03 ,Al 0.03 was made up by putting the powder between two glass microscope slides as seen in Figure 9a, the body color of the phosphor is orange-brown under white light illumination. In Figure 9b the sample from 9a is seen under 366 nm light excitation, its emission in the visible region is deep red.…”

Review of cost reduction methods in photoacoustic computed tomography

“…LED is a category of light sources that has been used in PACT system due to their extremely compact size, lightweight, long lifetime, and low-cost potentials. Although the fundamental process of light generation in LEDs is similar to LDs, LEDs do not generate stimulated emission [65]. Therefore, their optical spectrum is broad bandwidth, their spatial coherence is low, and they are not technically considered as laser sources.…”