In this article, optical switching effect of a thermochromic thin film is reported. The transmittance of the film increased
from 0.64 at 120°C to 0.96 at 200°C indicating strong temperature dependence for its optical properties. The
temperature dependence of the optical properties was found to be reversible during the heating and cooling processes.
The possibility to reduce the size of the laser beam with the nonlinear optical switching effect of the thermochromic
film is discussed.