In this work, we have investigated the transmission and Faraday rotation spectra of light from symmetric and asymmetric structures, which both contain a plasma layer. An external magnetic field is applied to the structures. For theoretical and numerical calculations, the 4 by 4 transfer matrix method has been utilized. The results showed that in symmetric and asymmetric structures, two and three defect modes appear in the photonic bandgap with different amplitudes, respectively. It is observed that enhanced Faraday rotation angles have been produced at the same frequency of the defect modes in the two structures. The tunability of the frequency of the defect modes, their transmission intensity, and corresponding Faraday rotation angles are studied by changing the layers’ number, the external magnetic field strength, and the electron density of the plasma layer. The Faraday rotation angle values of both structures show the noticeable changes by varying the layers’ number. For asymmetric and symmetric structures, the absolute maximum Faraday rotation angles are changed from 6° to 65°, and 5° to 70° respectively, by changing the layers number from 2 to 5. The obtained results may have potential applications in tunable filters of the millimetres-wavelength region.
