Nonlinear optical undergraduate experiments with porphyrin solutions and low power lasers

We present various nonlinear phenomena that can be visualized directly as variations of the beam cross section with laser beam powers beginning from a few mi1iwatts. Self-action effects Iike self-defocusing, and the measurement of the nonlinear refractive index can be performed using low power cw lasers and organic solutions of porphyrins. These experimenss are suitable for undergraduaee standard laboratories where nonlinear optical phenomena are to be demonstrated in a practical and simple fashion. Porphyrins solutions exhibit a sensitive photorefraction and are characterized by a large nonlinear coefficient.