Channel Plasmon-Polariton Guiding by Subwavelength Metal Grooves

We report on realization of channel plasmon-polariton (CPP) propagation along a subwavelength metal groove. Using imaging with a near-field microscope and end-fire coupling with a tapered fiber connected to a tunable laser at telecommunication wavelengths (1425–1620 nm), we demonstrate low-loss (propagation length $\sim 100\mu \mathrm{m}$) and well-confined (mode width $\cong 1.1\mu \mathrm{m}$) CPP guiding along a triangular $0.6\mu \mathrm{m}$-wide and $1\mu \mathrm{m}$-deep groove in gold. We develop a simple model based on the effective-index method that accounts for the main features of CPP guiding and provides a clear physical picture of this phenomenon.