Dielectric laser mirror with phase anisotropy

A description is given of a phase-anisotropic dielectric mirror for normal incidence of light, intended for a two-frequency gas laser emifflng linear orthogonally polarised modes. The phase of light reflected by this mirror depends on its polarisation, but its amplitude is independent of the polarisation. The mirror is a combination of a dielectric multilayer with an anisotropic component. The anisotropic component consists of one or several dielectric layers with a surface (relief) grating and a period shorter than the wavelength. The difference between the phases of the reflected light with two orthogonal linear polarisations increases with increase in the depth of the relief, but the amplitudes of the reflected light remain the same. The results of numerical calculations and of experimental tests of mirrors are reported.