Measurement of the focal length of a lens using a fiber optic Mach-Zehnder interferometer

Abstract

We present results of measurements of the focal length of thin lenses (convex and concave) using the fiber optic Mach-Zehnder interferometer developed in our laboratory (Optoelectronics, Physics Department, USC). The focal length of the test lens is determined by counting fringes in the unmagnified (pattern without the test lens) and magnified (pattern after passing through the test lens) interference patterns. The accuracy obtained is one order of magnitude higher than that of the techniques commonly used in the undergraduate laboratory courses (techniques based on the thin lens equation and image magnification). The method is simple and the setup is easy to handle.