Localized electromagnetic distortion in 2D metal hole array and its application to imaging of permittivity distribution

We performed two-dimensional imaging of conductive and dielectric samples above a metal plate with a two-dimensional array of subwavelength holes (metal hole array) with electromagnetic distortion formed by inserting a needle-like conductive probe into holes in it. A metal hole array has a special electromagnetic response such as localization of electromagnetic waves at a specific frequency near it. Generally, the phenomenon described above is called “spoof surface plasmon resonance.” And such special media can be regarded as “metamaterial” from a point of view that it realizes a macroscopically uniform medium by the subwavelength-size holes in the metal plate. We conducted numerical analyses of electric field profiles in order to clarify how electric field distributions near the metamaterial change by the electromagnetic distortion, and confirmed the phenomenon that these uniform electric fields around the “metamaterial” are distorted locally by using the needle-like conductive probe. Electromagnetic waves response to the permittivity at the space, so that it is considered that the change of the permittivity at the space is reflected as that of the electromagnetic distribution at the space. Based on the above, the formation of the electromagnetic distortion can be a detecting method of samples which have dielectric responses. Therefore, we consider that this two-dimensional imaging system is applicable to detecting something which has abnormal permittivity inside bulk material, such as a cancer in biomaterial tissues.