A comparative study of 1D metallic (Au, Ag, Cu, Al) thermal tunable photonic crystal filter with exponentially graded thickness

he transmission through a thermal tunable metallic ternary photonic crystal filter is investigated. The filter is assumed to possess symmetric thickness exponential gradation and mirror symmetry. The structure of the filter is (metal/SiO2/Si)N(Si/SiO2/metal)N, where the metal can be gold (Au), silver (Ag), copper (Cu) or aluminum (Al). The refractive index of the metal is assumed as a function of wavelength and temperature. The transmission peaks of the defect modes are studied in detail with both the angle of incidence and temperature. The performance of each metal is explored and compared with the non-graded filter. Many interesting features are found. The transmission peaks corresponding to TE modes are much sharper than those corresponding to TM modes. As the temperature increases, the transmission peaks shift toward larger wavelengths for all incidence angles.