A Historic Experiment to Demonstrate the Gouy-Phase

The find of a 100 years old calcite lens, cut in the optical axis by Dr.Steeg&Reuter in Bad Homburg, inspired us to use it as a polarizing interferometer for a demonstration of the Gouy-phase - with striking results. Enquiries showed that Pieter Zeeman (Zeeman effect, 1896) had already performed this Gouy-phase experiment with a lens from the same company (Versl.K.Ak. van Wet.Amsterdam.Afd. Natuurk. 6 11-13 (1887/88)) and ours was probably bought to repeat it. We show our version of Zeeman’s experiment and extend it to the caustics caused by the astigmatism of the tilted calcite lens. The quantitative analysis with a compensator is not really accurate, but the experiment allows a descriptive demonstration of the Gouy-phase. We discuss the momentum conservation at the confinement of waves in caustics as the physical origin of this peculiar phase and compare it with results from the paraxial approximation. It seems that the “flattened hamster” shown by the isophotes in the meridional plane of a lens focus (Born Wolf Fig.8.41) is a wonderful indication of a basic physical background, and gives deep reaching insights into wave and particle physics by means of the optical Gouy-phase.