A Cr3+ luminescence based ratiometric optical laser power meter

Abstract

Chromium doped luminescent phosphors display numerous spectral features that can be useful for designing modern multi-functional materials. Here we study GdAl₃(BO₃)₄ nanoparticles doped with Cr³⁺ ions, which enable combining efficient light-to-heat conversion and efficient luminescent properties in homogenously doped materials avoiding complicated syntheses of hetero-structural or hybrid-designed materials. In particular, while the intentionally increased content of Cr³⁺ ions leads to increased self-heating in a relatively broad photoexcitation spectrum, the concurrently occurring bright luminescence intensity ratio between the ⁴T_2(g) level and the ²E_(g) level responds to local temperature variation. Such behavior inspired us to evaluate the possibility of ratiometrically measuring the delivered laser pump power. The presented strategy enables the development of luminescent sensors operating in a wide range of power densities. It has been proposed and explained how the performance of the sensor, including sensitivity and usable excitation density range of optical density meter, can be modified by the knowledgeable optimization of the Cr³⁺ dopant ion concentration. We believe that this work may be the beginning of a new research direction that will allow the development of highly sensitive remote optical density meters.