2ND-HARMONIC GENERATION FROM THE QUADRUPOLE RESPONSE IN C-60 FILMS

By applying the numerically computed energy levels and wave functions of the pi electrons of the C60 molecule following the Su-Schrieffer-Heeger model, we calculated the second-order quadrupole nonlinear susceptibility x(zzzz)Q for the C60 medium and the calculated value is 1.7 X 10(-20) m2/V for the fundamental wave lambda = 1.064 mum. For the fundamental wave lambda = 1.064 mum, the second-order susceptibility chi(zzz)(2) caused by the second-order nonlinear quadrupole polarization has the magnitude 1.1 X 10(-13) m/V (i.e., 2.5 X 10(-9) esu). This result is in excellent agreement with the recent experimental measurements. In addition, we also calculated the quadrupole-induced reflection and transmission second-order harmonic generation by further considering the effect of finite film thickness.