Abstract

Alexandrite, or chromium-doped chrysoberyl (Cr³⁺: BeAl₂O₄), is known to be the first tunable laser crystal directly diode-pumped at room temperature (1979 Wallin et al [1]). Such lasers are used for medical application (especially dermatology), material processing and Lidar systems. Large absorption coefficients around 410 nm and 590 nm and long room temperature fluorescence lifetime (260 µs) enable traditional flashlamp pumping and red laser diode pumping [2]. Flashlamps being limited in efficiency and red laser diodes having limited performances in terms of output power, it is relevant to consider alternative pumping sources. Recent improvements in LED performance represent a new interesting opportunity for laser pumping. Indeed, LED are more robust, less expensive, extremely less sensitive to the external environment than laser diodes and they are in tremendous expansion with rapid performance improvement thanks to the lightning market. However, their brightness is still few orders of magnitude lower than laser diodes. We recently demonstrated that a luminescent concentrator (LC) can improve the LED intensity by one order of magnitude by overcoming the brightness conservation rule [3]. Here, we propose Alexandrite indirect LED-pumping via Ce-doped LCs.

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