Nonlinear optical effects in absorbing fluids: some undergraduate experiments

While nonlinear optics has become increasingly important in theory and applications few undergraduate laboratories include nonlinear optics experiments in their program. The purpose of the paper is to describe a few simple experiments and their theoretical interpretations at the senior undergraduate level. Liquids containing traces of absorbing dyes were used as the nonlinear media. Nonlinear effects such as self-diffraction and phase conjugation were observed with laser power as low as 100 mW.