Synchronized double L-scan technique for the simultaneous measurement of polarization-dependent two-photon absorption in chiral molecules.

We report on a double L-scan technique for the simultaneous measurements of polarization-dependent nonlinear absorption. The high sensitivity of this method resides on the synchronized measurements of "twin" laser pulses to compensate for energy and mode fluctuations in the sample. This technique was successfully applied to the accurate determination of two-photon absorption (2PA) circular dichroism and 2PA circular-linear dichroism in a chiral solution. To our knowledge, this is the first time these nonlinear optical effects have been accurately measured. Our technique is expected to lead efforts in the study of biological systems and in the design of metamaterials with a negative refractive index.