Nonlinear Optical Properties of Si Nanodot in ${\rm Al}_{2}{\rm O}_{3}$ Matrix

The linear and the third-order nonlinear optical properties associated with intersubband transitions are studied for spherical Si nanodot embedded in an amorphous
${\rm Al}_{2}{\rm O}_{3}$
matrix. The effect of radiation intensity and the change in the size of the dot are investigated on the nonlinear photoabsorption coefficient, refractive index change, and the third-order nonlinear optical susceptibility for transitions from ground state (1s-1p) and excited states (1p-1d, 2s-2p). The oscillator strength is also calculated for these transitions along with the photoelectric cross sections from the initial 1s and 2s states of the dot. It is noted that a decrease in the size of the dot leads to blue shift in peak positions of photoabsorption coefficient, refractive index change, and third-order nonlinear susceptibility involving transitions from the ground and excited states.