Propagation loss measurement for surface plasmon-polariton modes at metal waveguides on semiconductor substrates

Propagation losses were measured for surface plasmon-polariton (SPP) modes at metal waveguides on semiconductor substrates. The waveguides are simple strips of Au or Al deposited on InP substrates or 300-nm-thick SiO2 film covering the InP substrates. We used a direct method that can clearly discriminate SPP modes in vidicon-camera images, thereby allowing quantitative measurements. The loss coefficients measured at a wavelength of 1.55 μm were, as predicted by theory, in the range of 8.5–17 dB/mm, which shows the waveguides are feasible for practical applications.