Dielectric-loaded surface plasmon polariton waveguides on a finite-width metal strip

We investigate the guiding properties of a dielectric-loaded surface plasmon polariton waveguide on a finite-width metal strip. The guided mode is characterized by leakage radiation microscopy for different metal strip widths. We show a strong mode attenuation for metal strip widths below 1.75 mu m at telecom wavelength lambda=1.55 mu m. We estimate the minimal width using numerical methods and propose an original interpretation. Good agreement with the measured data is achieved. The determination of this critical width is a prerequisite for designing miniaturized plasmonics devices.