Intrinsic heating in NdxY1.00-xAl3(BO3)4 particles excited at 808 nm leads to bright multi-band up conversion emission via ladder-thermal excitation

Abstract

We investigate ladder-thermal excitation of trivalent lanthanide ions by exploiting upconversion and downconversion emissions in NdxY1.00-xAl3(BO3)4 particles, resonantly excited at 808 nm (4I9/2 → 4F5/2 + 2H9/2). Thanks to the intrinsic heating in the nonradiative relaxation pathways with phonon emissions from the Nd3+, we observed light emission from 530 nm to 1100 nm associated with Nd3+ electronic transitions. The upconverting emitting states were populated via ladder-thermal excitations starting from the 4F3/2 state, excited through nonradiative relaxation with phonon emissions from the 4F5/2 + 2H9/2 states. Our findings demonstrate that the intrinsic heating act as an important quenching mechanism for the well-known laser emissions arising from the 4F3/2 state (900 nm, 1064 nm, and 1320 nm). However, instead of converting the stored energy into heat, the loss of population from the 4F3/2 state results in multi-wavelength emissions. Corroborating the ladder-thermal excitations, we decorated the surface of the dielectric particles with silver nanoparticles, demonstrating an enhancement of the upconverted emissions due to the excitation of vibrational modes of the metallic nanoparticles which works as an additional heat source. Our findings have potential applications in generating bright broad-band emissions from lanthanide ions.