Optically active second-harmonic generation from a uniaxial fluid medium

We have shown that optically active second-harmonic generation is allowed in a uniaxial fluid medium. A homeotropically aligned chiral smectic-A liquid crystal was used as an example. Phase matching of chiral SHG in the medium was achievable by angle tuning and the chiral nonlinear susceptibility was deduced from the results. The SHG output vanished when the LC moved into the isotropic phase as expected. This work provides a method for us to measure chiral nonlinearity of chiral LC molecules, or more generally, chiral molecules that can be uniaxially aligned in a fluid medium.