TABLE OF CONTENTS Until now the treatment has been restricted to isotropic surfaces and bulk phases. In this chapter an extension will be given to surfaces between gyrotropic media. In such media the left-handedness or right-handedness of their structure manifests itself by phenomena like optical rotation and circular dichroism. The description of the optical properties of such gyrotropic media is well established [81, 20]. There are two prevailing methods. In the first method, due to Condon [82], both the polarization and the magnetization contain a contribution due to the chiral structure of the medium. This description has the symmetry for the interchange of the electric with the magnetic fields, which was used throughout this book. See for instance sections 8 and 9 in chapter 3 for the relevance of this symmetry in the general context. In the second method one uses an alternative description in which the magnetization is adsorbed in the polarization [81, 20, 83]. Both methods are fully equivalent and as such the second method, which only needs a dielectric tensor, is usually preferred.
As one needs boundary conditions to interpret measurements on such systems, a proper formulation of these conditions is needed. It is found that if one uses the standard boundary conditions, which are appropriate in the absence of singular contributions to the polarization and magnetization at the surface, cf. eq. (3.30) with P ? s = M s = 0, the above two methods lead to different reflection coefficients [84, 85, 86, 87, 88,...
