Zaihe Yu, Zhuoyuan Wang, Zhen Gao, and Zhengyong Song
Abstract: We theoretically demonstrate a
subwavelength surface-plasmon-polariton (SPP) microcavity on a planar metallic
surface working at terahertz regime with both high quality factor and
ultra-small mode volume. The microcavity is based on plasmonic and metamaterial
notions, and it consists of an easy-to-manufacture circular aperture and a
bell-shaped metallic core. It is shown that such a structure can sustain SPP
eigenmodes whose fields are tightly trapped within the microcavity. Using the
proposed structure, total Q factor of 1000 (including losses from metals at low
temperatures) and subwavelength mode volume of 0.00018(λ/2n)3 can be achieved
in the THz range for fundamental surface-plasmonic eigenmodes at room
temperature. Moreover, the key figures of merit such as resonance frequency can
be flexibly tuned by modifying the geometry of the microcavity, making it
attractive for broad applications in filters, light sources, energy storages
and on-chip optical communications.
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