Thin-film helicoidal bianisotropic medium (TFHBM) layers with large local linear birefringence are fabricated using the serial bideposition technique. The viability of axially excited TFHBM layers as circular polarization filters is experimentally demonstrated. The presence of index-matched cover and substrate media is shown to enhance the filter performance of a TFHBM layer. A thinner TFHBM layer is required for adequate performance when the local linear birefringence is higher. © 2000 Society of Photo-Optical Instrumentation Engineers.