It is shown that the matrix describing a general (transparent or absorbing)
multilayer is an element of the group SL(2, C), which is locally isomorphi
c to the (3 + 1)-dimensional restricted Lorentz group SO(3, 1). In conseque
nce, a natural identification of the multilayer reflection and transmission
coefficients with the parameters of a Lorentz transformation is performed.
The correspondence between electric field and space-time variables is disc
ussed as well. (C) 1999 Optical Society of America [S0740-3232(99)00608-0].