Investigation of laser-induced luminescence saturation in a single-crystal YAG:Ce phosphor: Towards unique architecture, high saturation threshold, and high-brightness laser-driven white lighting

Abstract

A significant obstacle in the development of phosphor-converted white-laser diodes (pc-wLDs) is associated with the laser-induced luminescence saturation of phosphors. YAG:Ce is a canonical yellow-emitting phosphor. However, there has been no few systematic research of measurement and understanding of the luminescence saturation in YAG:Ce yet. Here, we analyze the luminescence saturation of a single-crystal YAG:Ce with a unique phosphor geometry. A novel characterization method, which enables the optical signals to be fully collected and analyzed, is introduced. The effects of both laser power and laser power density on the luminescence properties and colorimetric properties of the YAG:Ce are studied systematically. The results show that a single-crystal YAG:Ce has a high saturation threshold (over 360 W/mm 2 ) so that only a very slight saturation behavior can be observed at a high power density. Furthermore, a pc-wLDs light source based on the combination of a single laser diode and a YAG:Ce phosphor exhibits remarkable efficiency and stability. Under the excitation of a 3.38 W blue laser (~100 W/mm 2 ), the white light emission with the luminous flux of 465 lm, the luminous 2 / 23 efficacy (LE) of 145 lm/W, and the correlated color temperature (CCT) of 4980 K can be achieved.

YAG:Ce3+ Transparent Ceramic Phosphors Brighten the Next‐Generation Laser‐Driven Lighting

“…[25] The traditional encapsulated technique is dispersing YAG:Ce 3+ phosphors in organic binders that have a lower heat resistance and thermal conductivity (0.1-0.4 W m −1 K −1 ). [26] To overcome the thermal effect induced by the high-power density of blue LDs, remote encapsulations of single-crystal phosphors (SCPs), [27][28][29] phosphor in glasses (PiGs), [30][31][32][33] and transparent ceramic phosphors (TCPs) [11,22,[34][35][36][37][38] are proposed. The TCP is most promising type due to its lower cost and higher thermal conductivity than the SCP and PiG type.…”

Unique Design Strategy for Laser‐Driven Color Converters Enabling Superhigh‐Luminance and High‐Directionality White Light

“…Firstly, the phosphor materials must withstand long‐term high flux density laser irradiations and dissipate the generated heat within the small laser spot. Based on this guideline, a variety of robust phosphor ceramics and luminescent single crystals, especially Y 3 Al 5 O 12 (YAG)‐based materials, have been studied . However, the high refractive index of crystalline materials causes a quite small critical angel and thus strong total internal reflection (TIR), seriously deteriorating the light extraction efficiency .…”

Phosphor material dependent spot size limitations in laser lighting

“…This is the main reason that laser lighting is now being implemented in car headlights and projectors. Many studies have focused on investigating colorimetric properties and luminescence saturation in phosphors due to the high incident power density [3][4][5][6][7][8]. Only few studies have investigated the light distribution from the phosphor converted laser lighting and mainly with the focus of simulating the heat distribution in the phosphor materials [9][10][11][12].…”