Effect of laser speckle on light from laser diode-pumped phosphor-converted light sources

Design and operation of a hybrid LED/LD-pumped phosphor-converted white-light lamp

Illumination sources based on phosphors, pumped by laser diodes (LDs), have seen rapid developments over the past decade. Here, we present a new, to the best of our knowledge, design that features both spectral richness and the capability for high brightness. Complete design details and operational characterization have been described. This basic design can be extended in various ways to customize such lamps for different operational requirements. A hybrid arrangement of both LEDs and an LD is used to excite a mixture of two phosphors. The LEDs, in addition, provide a blue fill-in to enrich output radiation and to tune the chromaticity point inside the white region. The LD power, on the other hand, can be scaled up to generate very high brightness levels that are not achievable with pumping from LEDs alone. This capability is gained using a special transparent ceramic disk that carries the remote phosphor film. We also show that the radiation from our lamp is free from speckle-producing coherence.

Unique Color Converter Architecture Enabling Phosphor-in-Glass (PiG) Films Suitable for High-Power and High-Luminance Laser-Driven White Lighting

As a next-generation high-power lighting technology, laser lighting has attracted great attention in high-luminance applications. However, thermally robust and highly efficient color converters suitable for high-quality laser lighting are scarce. Despite its versatility, the phosphor-in-glass (PiG) has been seldom applied in laser lighting because of its low thermal conductivity. In this work, we develop a unique architecture in which a phosphor-in-glass (PiG) film was directly sintered on a high thermally conductive sapphire substrate coated by one-dimensional photonic crystals. The designed color converter with the composite architecture exhibits a high internal quantum efficiency close to that of the original phosphor powders and an excellent packaging efficiency up to 90%. Furthermore, the PiG film can even be survived under the 11.2 W mm^-2 blue laser excitation. Combining blue laser diodes with the YAG-PiG-on-sapphire plate, a uniform white light with a high luminance of 845 Mcd m^-2(luminous flux: 1839 lm), luminous efficacy of 210 lm W^-1, and correlated color temperature of 6504 K was obtained. A high color rendering index of 74 was attained by adding a robust orange or red phosphor layer to the architecture. These outstanding properties meet the standards of vehicle regulations, enabling the PiG films with the composite architecture to be applied in automotive lighting or other high-power and high-luminance laser lighting.