Resonant Transmission of Electromagnetic Wave Through Small Apertures

Authors: Young Ki Cho

Source: FERMAT, Volume 30, Communication 5, Nov.-Dec., 2018

Abstract: Two types of transmission resonant structures which can provide both high spatial resolution and high transmission are discussed. One is a transmission-resonant aperture(TRA) type and the other is a transmission-resonant cavity(TRC) type, which are useful in designing so called subwavelength(or nano) aperture for the NSOM(Near field scanning optical microscope) probe. There are two types of TRC structures. One is a conventional TRC structure, a coupling-aperture-type(CA type) TRC which has been used as a band pass filter(BPF) in microwave band. The other is a perforated-aperture-type(PA type) TRC such as narrow rectangular slot and ridged slot structures perforated on the thick conducting screen. The PA type TRC are investigated for the two kinds of transmission resonances, Fabry-Perot(longitudinal resonance) type and transverse resonance type. The desired nano-aperture in the NSOM probe design as a TRA can be found by letting the conductor slab thickness be zero for the transverse resonance condition observed in the PA type TRC on the thick conducting screen.

Index Terms: Bethe’s small hole theory, transmission efficiency, transmission efficiency through the aperture, Transmission resonant aperture(TRA), Transmission resonant cavity(TRC) Fabry-Perot(longitudinal resonance), ENZ(transverse resonance)

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Resonant Transmission of Electromagnetic Wave Through Small Apertures