  Inspired by the capability of structured illumination microscopy in
subwavelength imaging, many researchers devoted themselves to investigating
this methodology. However, due to the free propagating feature of the
traditional structured illumination fields, the resolution can be only improved
up to double times compared with the diffractied limited microscopy. Besides,
most of the previous studies, relying on incoherent illumination sources, are
restricted to fluorescent samples. In this work, a subwavelength nonfluorescent
imaging method is proposed based on the terahertz traveling wave and plasmonics
illumination. Excited along with a metal grating, the spoof surface plasmons
are employed as the plasmonics illumination. When the scattering waves with the
SSPs illumination are captured, the high order spatial frequency components of
the sample are already encoded into the obtainable low order ones. Then, an
algorithm is summarized to shift the modulated SF components to their actual
positions in the Fourier domain. In this manner, high order SF components
carrying the fine information are introduced to reconstruct the desired
imaging, leading to an improvement of the resolution up to 0.12 lambda.
Encouragingly, the resolution can be further enhanced by tuning the working
frequency of the SSPs. This method holds promise for some important
applications in terahertz nonfluorescent microscopy and sample detection with
weak scattering.
