How to calculate the amplitude P(2*\omega)? How to estimate numerically the amplitude of the dipole?

A laser beam carrying 1 W of power is focused to a spot size of 30 \mu*m diameter in a crystal having a refractive index of n=2 and a second-order susceptibility of \xi^{(2)}=10^{-7}[Gauss system]. Calculate the amplitude P(2*\omega) of the component of the nonlinear polarization oscillating at frequency 2*\omega. Estimate numerically the amplitude of the dipole moment per atom \mu*(2*\omega) oscillating at frequency 2*\omega by assuming that the atom density is 10^{22} cm^{-3}.