We investigated the properties of magnetoactive cholesteric liquid crystals (CLCs) being in external static magnetic field directed along the helix axis in the case of light oblique incidence. We showed that at oblique light incidence complex band structure is observed in the first-order reflection band. In this case there appear two new photonic band gaps (PBGs). The frequencies of these new regions and their frequency widths in significant intervals can be tuned by changing the external magnetic field and the angle of incidence. The polarization of reflected light in these regions can be tuned, too: we can obtain light with right circular polarization instead of left circular polarization light or vice versa by reversing the direction of the external magnetic field. This system is nonreciprocal and the nonreciprocity changes over a wide range. This system can operate as a tunable optical diode for both orthogonal circular and orthogonal linear polarizations. We investigated the features of the wave vectors of Bloch waves excited in magnetoactive CLCs in an external magnetic field with the direction of light propagation oblique with respect to the helix axis. We showed that new Dirac points appear on both sides of the main PBG. And it is at these Dirac points that new PBGs appear. We investigated the light localization peculiarities in this structure too.

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• Magneto-optical spectra
• Polarization
• Band structure methods
• Bloch wave theory
• First-principles calculations