COMPARISON OF LINEARLY AND CIRCULARLY-POLARIZED PROBES OF 2ND-ORDER OPTICAL-ACTIVITY OF CHIRAL SURFACES

We compare two nonlinear-optical techniques for measuring chirality of isotropic surfaces. One technique measures the difference in the effi ciency of surface second-harmonic generation between the cases of left -hand and right-hand circularly polarized fundamental light and the ot her measures the difference in the efficiency between the cases of fun damental light linearly polarized -45 degrees and +45 degrees with res pect to the p-polarized direction. A nonzero difference in either case indicates chirality, where no difference should be measured for an is otropic achiral surface. We examine the complementariness of these two techniques theoretically and experimentally. In experiments utilizing thin films of a chit-al poly(isocyanide), we measure the second-harmo nic response as a function of the state of polarization of the fundame ntal light when manipulated by both quarter and half waveplates. We ex tract the circular and Linear differences from these more complete mea surements and find the largest circular and linear differences to be 2 3% and 118%, respectively. (C) 1996 American Institute of Physics.