Broadband laser induced white emission observed from Nd3+ doped Sr2CeO4 nanocrystals

Broadband anti-Stokes laser induced white emission (LIWE) of high intensity was observed from Sr2CeO4:Nd3+ nanocrystals with various dopant content illuminated by focused infrared excitation lines under reduced pressure conditions. The nanocrystals were synthesized using a sol-gel method. The phase purity of the samples was confirmed through X-ray diffraction measurements. Basing on those results, the average grain sizes of the Sr2CeO4:Nd3+ were determined to be 68 and 72 nm for dopant content equal to 1% and 20%, respectively. In order to investigate the LIWE mechanism, the power and pressure dependences for two independent excitation lines were recorded. It was found that the emission spectra upon 808 nm irradiation exhibit Stokes and anti-Stokes emission, varying in magnitude with excitation power density. Furthermore, a red shift of the emitted light spectrum was observed for the increased dopant concentration in the investigated nanocrystals. Photoconductance measurements showed a significant change of electrical resistance under infrared laser irradiation, with evident influence of dopant content on the photoresistance being observed. Finally, the mechanism of LIWE generation process was proposed.