The characteristics of photonic forbidden bands,transmission gain and absorption of one-dimensional (1D) dual-periodical photonic crystals (PC) with a complex dielectric layer were studied by using the optical transfer matrix (TM) method.The results show that the photonic band gap (PBG) of this structure is enlarged and many transmission resonance peaks appear in PBG.Large transmission gain for transmission peaks is obtained if the imaginary part of dielectric constant is negative.With the increase of the absolute value of the imaginary part,the transmission gain increases firstly and the transmittance gain gets to an apex.The imaginary parts of dielectric constant corresponding to transmission gain apex are different according to wavelength.However,the transmission ratio of resonance peaks is less than 1 if the imaginary part of dielectric constant is positive.The properties might be used to design multi-narrow-channel band filters and optical amplification devices synchronously.
