Third-Order Nonlinear Optical Properties of Substituted Polyphenylacetylenes

Abstract

Third-order harmonic generation (THG) and electroabsorption (EA) in substituted polyphenylacetylenes (PPAs) which are examples of onedimensional π-conjugated polymeric systems have been studied. The values of x ⁽³⁾(-3ω;ω,ω,ω) obtained from THG measurement for substituted PPAs increase with increasing λmax of absorption. The dispersion of x ⁽³⁾ (-ω;ω,0,0) for PPA film derived from Kramers-Kronig transformation of optical absorption change under the electric field (EA spectra) has been observed, and it shows the similar shape of the second derivative of the optical absorption spectra. The typical value of x ⁽³⁾(-ω;ω,0,0) for o-substituted PPA was determined to be ca. 10⁻¹¹ esu.