Abstract

Since the early 2000s, light-emitting diodes (LEDs) have simultaneously known a dramatic improvement of their performance and a drastic cost reduction making LEDs the most efficient and affordable light sources for lighting. However, their irradiance is limited to few hundreds of W/cm². To go beyond LED’s limited irradiance, the combination of LEDs with concentrators represents an elegant and simple solution [1]. Indeed, luminescent concentrators have the property to increase the irradiance by one order of magnitude with a process of absorption/emission in a high index medium where the light is confined by total internal reflection. Useful for direct applications in lighting [2,3], luminescent concentrators can cover many spectral bands in the visible and in the near infrared by an appropriate choice of the couple LED /crystal. As a matter of fact, Ce:doped concentrators pumped by blue LEDs are one of the brightest incoherent sources in the visible (between 550 nm and 650 nm). As rugged, simple and low cost sources, they give unique opportunity to pump transition metal gain media such as Ti:sapphire, Cr:LiSAF and Alexandrite (Cr³⁺:BeAl₂O₄) whose absorption bands are in the visible. This paper gives an overview of the performance obtained with those three gain media pumped by Ce:doped LED pumped luminescent concentrators. Much more than first laser demonstrations [4-6] this paper describes how LED pumped transition metal lasers are inserted in laser systems for a step further, towards applications.

© 2019 IEEE