A novel TM-pass polariser using the form birefringence of a stratified periodic medium is proposed. The mode-filter properties of a planar waveguiding structure with form birefringent buffer layer on a lossy substrate are investigated numerically. A structure with TM0-mode attenuation of less than 3 dB/cm at λ0 = 633 nm and TE-mode losses exceeding 300 dB/cm has been demonstrated experimentally. © 1991, The Institution of Electrical Engineers. All rights reserved.