Laser induced broad band white emission from transparent Cr4+:YAG ceramics: Origin of broadband emission

Abstract

Laser-induced white (light) emission was observed from transparent Cr4+:YAG ceramics irradiated with a focused continuous wave beam of light from an infrared laser diode. The laser-induced white emission is detected only on the surface of the sample and is not observed in volume. It is found that the intensity of the emission increases exponentially with the laser power density above the threshold. The impact of broadband emission on the power of the transmitted laser beam through the sample was measured. The disappearance of broadband emission due to displacement of the laser beam or an increase in ambient pressure leads to a decrease in the power of transmitted laser beam. Origins of the laser-induced white light emission along with its characteristic features are discussed in terms of multiphoton absorption, intervalence charge transfer and ionic space charge models.