  Light-assisted micro-nanoscale temperature control in complex nanoparticle
network attracts lots of research interests. Many efforts have been put on the
optical properties of the nanoparticle networks and only a few investigations
on its light-induced thermal behavior was reported. We consider two-dimensional
(2D) square-lattice nanoparticle ensemble made of typical metal Ag with a
radius of 5 nm. The effect of complex optical coupling and thermal accumulation
on the light-induced thermal behavior in plasmonic resonance frequency (around
383 nm) is analyzed by means of the Green\textquotesingle s function approach.
Regime borders of both optical coupling and thermal accumulation effects on the
photothermal behavior of 2D square-lattice nanoparticle ensemble are figured
out clearly and quantitatively. A dimensionless parameter $\varphi$ is defined
as the ratio of full temperature increase to that without considering the
optical coupling or thermal accumulation to quantify the optical coupling and
thermal accumulation effects on photothermal behavior. The more compact the
nanoparticle ensemble is, the stronger the optical coupling on thermal behavior
is. When the lattice spacing increases to tens of nanoparticle radius, the
optical coupling becomes insignificant. When $\varphi \approx 1$ (lattice
spacing increases to hundreds of nanoparticle radius), the thermal accumulation
effects are weak and can be neglected safely. The polarization-dependent
distribution of temperature increase of nanoparticles is observed only in the
compact nanoparticle ensemble, while for dilute ensemble, such
polarization-dependent temperature increase distribution can not be observed
anymore. This work may help for the understanding of the light-induced thermal
transport in the 2D particle ensemble.
