  Under infrared ultrashort pulse laser stimulation, we investigated
temperature-dependent second-harmonic generation (SHG) from nitrogen-vacancy
(NV)-introduced bulk diamond. The SHG intensity decreases in the temperature
range of 20-300 $^{\circ}C$, due to phase mismatching caused by refractive
index modification. We discovered that optical phonon scattering outperforms
acoustic phonon one in NV diamond by fitting the temperature dependence of SHG
intensity using a model based on the bandgap change via the deformation
potential interaction. This study presents an efficient and viable way for
creating diamond-based nonlinear optical temperature sensing.
