The planewave re ection/transmission characteristics of a chiral sculptured thin film (CSTF) were investigated numerically. The helical nanowires of the CSTF were taken to be made from a dissipative material while the void regions between the nanowires were filled with an active material. Theory showed that the CSTF can simultaneously amplify left-circularly-polarized incident light and attenuate right-circularly-polarized incident light, or vice versa depending upon the handedness of the CSTF. The presence of both dissipative and active materials allows the high reflectance to exceed unity for incident light of one circular polarization state across a substantial portion of the circular Bragg spectral regime but not for incident light of the other circular polarization state. That is, the chosen CSTF is a circular Bragg supermirror for one, and only one, circular polarization state.