A dual-band dichroic polarizer is provided for converting linearly polarized electromagnetic energy within distinct frequency bands into oppositely polarized circularly polarized electromagnetic energy. The polarizer includes an array of unit cells distributed across a sheet, wherein the unit cells each include a stack of one or more resonant structures, the stack configured to introduce a phase differential of approximately +90° to linearly polarized electromagnetic energy within a first distinct frequency band that is incident upon and passes through the sheet, and configured to introduce a phase differential of approximately −90° to linearly polarized electromagnetic energy within a second distinct frequency band, separate from the first distinct frequency band, that is incident upon and passes through the sheet, a linear polarization of the electromagnetic energy in the first distinct frequency band and a linear polarization of the electromagnetic energy in the second distinct frequency band being the same.