Prospects for 4-laser white-light sources

Abstract

This paper describes a series of simulation experiments designed to demonstrate the feasibility of using solid-state lasers in white-light mixtures. The mixed-laser sources are evaluated in terms of the luminous efficacy of the radiation (LER) as well as different measures of colour performance. The latter include the CIE colour rendering index (R a) and the IES colour fidelity index (R f) as well as a selection of additional parameters in the two systems. Optimization of the mixtures is achieved by the use of purpose-designed differential evolution algorithms. The best results to date (with four real laser wavelengths) are R f of 84 with LER 364 lm/W, which indicate the feasibility of the mixed-laser approach to provide highly efficient, energy-saving light sources. These prospects will be further enhanced by potential future developments in semiconductor lasers, with the possibility of producing R f of 86 with LER of 380 lm/W.

High-efficiency, low-speckle contrast white laser lighting via multi-stage scattering and photon recycling

“…Table 4 summarizes the white light illumination performance of the experimentally implemented reflective cavity CM-LD and PC-LD white light sources in cool white (4000-5000 K) and daylight (5000-6000 K) color temperature ranges. In principle, LER of four lasers with yellow LD can be as high as 330 lm/W, 7,8 so the LEO could be as high as 200 lm/Wo with CRI >85 using our existing extended cavity prototype (with a light extraction efficiency of 𝜂 𝑒𝑥 ~60%). Using more perfect DBR reflectors in the interior, 𝜂 𝑒𝑥 ~80% could be achieved based on Table 3, and the LEO can potentially reach >260 lm/Wo.…”

“…4 Similar to LED lighting, the available architectures for LD-based light sources include phosphor conversion (PC) 5,6 and direct color-mixing (CM). 7,8 PC-LDs can achieve high color rendering index (CRI) and reduce the coherence-induced laser speckles by scattering the laser beam. 9,10 It has been applied to automobile lamplights, featuring 1000 times brightness with 30% energy saving compared to their LED counterparts.…”

“…CM-LD lighting can potentially surpass PC-LD and achieve a high luminous efficacy of radiation (LER) of 350 lm/W and high color performance (CRI ~ 85) by carefully choosing the constituent laser line spectra in Blue-Green-Yellow-Orange (BGYO) scheme. 7,8,12 Currently, the limited efficiency of green and yellow lasers are the bottleneck. On the other hand, the advances in high-efficiency lasers (particularly yellow/amber/orange LDs) and sophisticated design of optical, electronic and heat-sink systems may speed up the development of CM-LD white lighting.…”

Artificial Intelligence in Light-Source Design

“…Our investigations in this field [28,32] were inspired by the work of Neumann et al [33] who successfully demonstrated a white-light 4-laser mixture with acceptable colour properties expressed in terms of the CRI and CQS metrics. Our earlier paper [28] also used CRI and CQS as measures of colour rendition.…”

“…Our purpose in [32] was to optimise similar mixtures of solid-state lasers, and to utilize the more up-to-date method of the IES colour fidelity index R f [15,16].…”