Optical properties of a deformed short pitch helical structure

We analyse via a homogeneous description the optical properties of a deform ed short pitch helical structure, which consists of an uniaxial mesoscopic medium in which the helical axis does not coincide with the direction of pe riodicity. We find that the effective medium is generally anisotropic, biax ial and gyrotropic. Its dielectric tensor is isotropic only in the limiting case of a proper chiral smectic C at its critical tilt angle.