Crystal birefringence is derived from the anisotropy of crystalline molecules and its unit cell.Actually,the anisotropic microstructures of thin films also induce optical anisotropy,which are the so-called sculptured thin films (STFs).[1] Since the emergence of the obliquely deposited thin film technique,the applications of sculptured thin films are greatly anticipated and considerable attentions have been received in the effects of different treatment processes on the optical properties of sculptured thin films.[2,3] With the development of substrate sweep technology[4] and the serial bideposition (SBD) technique,[5] the stable and controlled nanostructures of glancing angle deposition (GLAD) thin films,e.g.oblique column,[6] helix,zigzag,[7,s] polygonal spirals,[9] and superhelices,[10]can be easily obtained.Furthermore,a series of optical devices,such as polarizers,[11] circular-polarization filters,[12] and phase retardation plates,[13] have been investigated,among which the phase retardation plate is one of the most interesting components.