Relationship of the relative shift of the interference fringes and the absorption of light by a semitransparent metallic layer in a two-beam interferometer

Abstract

The relative phase shifts of equal-slope interference fringes have been measured on the two output images in a two-beam interferometer. Observations were made in the visible region for twelve semitransparent layers composed of various metals. It is shown that the difference of the relative shifts can be satisfactorily explained if it is assumed that, depending on the phase of the interference, the absorption of a semitransparent metallic layer varies from zero to twice its value. Based on this assumption, a formula is obtained that connects the absorption of a semitransparent metallic layer without interference and the relative shift of the interference fringes. A comparison is made of the measured absorption of the semitransparent layers with the values computed from this formula and the observed relative shifts. Comparison of the measured shifts with the optical constants of the metals showed that the shift of the fringes decreases as the refractive index of the metal from which the semitransparent layer is fabricated increases. The practical application of these results is discussed.