Phase shift and penetration depth of metal mirrors in a microcavity structure

Optical properties of metal films, such as phase shift on reflection or penetration depth of electromagnetic waves into mirrors, play an important role in determining the resonance wavelength of a microcavity. We created a series of lambda/2 cavities with a symmetrical structure of glass/Ag/lithium fluoride/Ag by changing the thickness of the Ag film. The penetration depth at different thicknesses of Ag film was obtained from the transmittance peaks of the cavities. Phase shift on reflection at the lithium fluoride-Ag interface was calculated based on the measured optical constants. The formulation between phase shift and penetration depth was proved by experimental results, which are in good agreement with the theoretical calculations.