Understanding a spectral response in a metal–dielectric–metal cavity structure: The role of constituent metals

Understanding optical interference in multilayer structures is of critical importance for designing a variety of optical coatings that have been widely used as an essential element in diverse applications. We demonstrate that the transition of reflective properties from a valley to a peak occurs by a metal on the incident side in a cavity structure comprising a transparent dielectric medium surrounded by two metals. The reflected light destructively interferes giving rise to a reflection dip when there is a large difference between the refractive index and the extinction coefficient of the metal, whereas a constructive interference occurs with the refractive index that is comparable to the extinction coefficient yielding a reflection peak. In addition, an admittance and an electric field distribution of the cavity structure are investigated with different constituent metals. Our results described in this paper provides a better understanding of the fundamental principles of the optical cavity, thereby potentially extending the range of possible future applications.