Fig. 1. Diagram of proposed structure with (a) sandwich structure composed of two layers of WSM separated by a dielectric layer and (b) wavelength dispersions of permittivity and effective permittivity.

Fig. 2. Contours of the transmittance of the proposed structure as a function of twist angle and wavelength. (a) and (b) represent the transmittance of light from TM to TE polarization in the forward and backward incidence, respectively. (c) and (d) represent the transmittance of light from TM to TM polarization in the forward and backward incidence, respectively.

Fig. 3. Contours of the ellipticity as a function of twist angle and wavelength. (a) is for the forward incidence, and (b) is for the backward incidence. (c) The relationship between the twist angle and ellipticity for forward (blue line) and backward (red line) incidences at the wavelength of 5.36 µm.

Fig. 4. Contours of the transmittance and reflectance as a function of incident angle and wavelength. In (a) and (b), the transmittance and reflectance of an incident TE-polarized light on the nonrotating single-layer WSM are represented, respectively. Similarly, in (c) and (d), the transmittance and reflectance of an incident TM-polarized light are represented.

Fig. 5. Explanations of unidirectional conversion between (a) orthogonal linear polarizations and (b) nonreciprocal conversion of light from linear to elliptical polarization.

Fig. 6. Contours of the transmittance of the proposed structure as a function of incident angle and wavelength, in which twist angle φ = 120°. (a) and (b) represent the transmittance of TM-to-TE polarization light in the forward and backward cases, respectively.

Fig. 7. Contours of the polarization conversion rate as a function of incident angle and wavelength, in which twist angle φ = 120°. (a) is for the forward incidence and (b) is for the backward incidence. (c) Isolation loss and insertion loss as a function of wavelength.