Air-spaced zero-order waveplate consists of two multi-order quartz waveplates separated by a spacer to form an air gap. It has a high damage threshold and can generate a corresponding incident/2 or incident/4 optical path difference. By aligning the fast axis of one waveplate with the slow axis of the other, a composite retardation plate is formed. The net retardation is the difference between the retardations of the two waveplates. Air-gap zero-order waveplates are less affected by temperature and wavelength than multi-order waveplates.