Hybrid plasmonic waveguide Bragg gratings (HPWBGs) are promising and essential components in ultracompact integrated circuits. In this paper, the transmission spectra of HPWBGs composed of two types of HPWs with different low-index dielectric layers are calculated through the transfer matrix method. Admittance match theory is used to analyze and improve transmission properties. Two admittance-matching conditions (the complete matching and the conjugate matching) are illustrated to optimize the transmission spectra effectively in specific passband, and the properties of bandgaps are also influenced. The results demonstrate the feasibility of the admittance match theory in modulating the transmission spectra of HPWBGs and this work provide a design approach for HPWBGs with a small footprint.
