  In the anti-Stokes excitation of trivalent rare-earth ions (RE3+), the
excitation photons energy is smaller than that of a given absorption
transition, and the energy mismatch can be compensated by phonons annihilation
from the host lattice. Since the phonon occupation number increases with
temperature, heating the system generally increases the efficiency of
anti-Stokes excitation. Here, we exploited the intrinsic heating associated
with light-to-heat conversion in the interaction of excitation laser light with
metallic nanoparticles (Ag or Au) on the surface of submicrometric particles of
NdxY1.00-xAl3(BO3)4 (x = 0.10, 0.20, and 1.00) in order to enhance the
efficiency of the anti-Stokes excitation at 1064 nm. Several upconversion
emissions are observed from 600 nm to 880 nm, the most intense being at 750 nm
due to the Nd3+ transition {4F7/2, 4S3/2} - 4I9/2. Giant enhancements are
demonstrated, when compared to undecorated NdxY1.00-xAl3(BO3)4 particles. The
present results can be expanded to other luminescent materials as well as
excitation wavelengths.
