Resonant Second-Harmonic Generation in the Exciton Region of CuCl and ZnO

Using a pulsed tunable dye laser pumped by a Q-switched ruby laser, the frequency dependence of second-harmonic generation has been measured in the region of the first and second $1s$ excitons of CuCl from about 3.18 to 3.34 eV and the region of the C exciton of ZnO from about 3.38 to 3.48 eV. From the data, the frequency dependence of the optical nonlinear susceptibility has been determined using linear optical constants calculated by a Kramers-Kr\"onig analysis of reflectivity. The results for the single nonzero term of the nonlinear susceptibility of CuCl and the two terms dzzz and dzxx of ZnO have been fit theoretically by an anharmonic-oscillator model employing two oscillators.