Abstract

We present the first report of quasi-phasematched third harmonic generation. Structures possessing the ability to generate quasi-phasematched third harmonic radiation have been fabricated, mathematically modelled and demonstrated experimentally. The effect has been observed in multilayer doped sol-gel derived nano-composite materials. Thin highly nonlinear dye-doped films have been deposited on 300µm thick substrates. These units are stacked together to form a periodic structure. The experimental configuration is shown in fig. 1. The structure is rotated in the path of a 20mJ pump beam. The third harmonic signal generated in each of the films adds up constructively at a few specific angles (as shown in fig.2). The third harmonic signal is a maximum when the separations between adjacent oscillators is equal to a multiple of the coherence length in the composite material.

© 1996 IEEE