Spatial self-phase modulation: a second instructive and low-cost demonstration of a nonlinear optical effect

Abstract The traditional teaching of general physics at undergraduate level usually restricts to linear optics, neglecting the nonlinear optics which plays an increasingly important role in several areas of technological development. This paper discusses the proposal of a simple and low cost experiment for the demonstration of the nonlinear optical effect called spatial self-phase modulation. This experiment completes the proposal of low cost experiments in the demonstration of nonlinear optical effects that began with the demonstration of the so-called thermal lens in a previous paper. Spatial self-phase modulation is based on the introduction of an additional term in the phase of a Gaussian wave incident on a medium as a consequence of its heating by the beam. As a nonlinear medium it is proposed to use a simple and low cost fluid such as soy sauce (shoyu sauce), whole grape juice or cola soft drink.