Abstract
In this study, the general treatment to obtain negative/positive giant Goos-Hänchen shifts for a slab cavity is provided. We find that there are two main types of giant shifts: The first type (type I) is associated with near-zero reflection coefficient, and the second type (type II) is associated with extra-large reflection and transmission coefficients. An infinite number of modes for each type are found. The general equations for both types with the model's parameters are presented to exactly locate the modes. Type I appears with near-zero absorption/gaining, while Type II appears with a finite gaining with values depend on the modes. The real values of the modes' susceptibility are found to be almost the same. Both types can generate negative or positive lateral shifts when the susceptibility is slightly modified. We finally present a discussion about their physical explanation and potential applications.