ABSTRACT
In recent years, solid-state lighting, based on light-emitting diodes (LEDs), has emerged as one of the most prominent developments in lighting technology. Their applications have proliferated over the course of the past decade and LED “bulbs” can now be found in most homes and offices. This transformation from traditional incandescent and fluorescent luminaires to LED-based lighting has been greatly celebrated. However, it has become evident that LED-based luminaires also have a serious weakness that limits their electricity-to-light conversion efficiency. This limitation arises from the “droop effect” in LEDs that reduces their conversion efficiency at high drive currents. This is a very serious shortcoming because it makes it impossible to construct compact, low-cost, high-brightness LED-based light sources. The way forward is then to replace LEDs with laser diodes (LDs) for pumping wavelength down-conversion phosphors, as LDs do not show the droop effect. This chapter discusses the advantages of this approach for solid-state lighting. The history of electric lighting and LEDs is briefly discussed, followed by a discussion on possible strategies for implementing solid-state lighting with LDs. Various components of LD-based luminaires such as pump LDs, optics, electronics, and phosphors are described. The design and simulation of typical LD-pumped phosphor-converted light sources are described, followed by a look at possible future developments.
