Low-Cost Nonlinear Optics Experiment For Undergraduate Instructional Laboratory And Lecture Demonstration: A Second Experiment

This communication presents a second simple and affordable experiment on nonlinear optics which is suitable for an undergraduate educational laboratory and is useful as a tabletop demonstration in a lecture on nonlinear optics. The experiment is based on the spatial self-phase modulation of a laser beam that generates in the far-field a typical pattern of interference rings. Such a nonlinear optical effect is due to thermally induced changes on the phase of a Gaussian laser beam that impinges on an optically absorbing medium. As the absorber, we propose to use a commercial soy sauce or grape juice, both of which are sold in supermarkets and exhibit strong optical absorption. The activities proposed for the experiment allow us to obtain the nonlinear refractive index of the sample.