Nanofocusing with channel plasmon polaritons.

We investigate radiation nanofocusing with channel plasmon polaritons (CPPs) propagating along subwavelength metal grooves that are tapered synchronously in depth and in width. Efficient CPP nanofocusing at telecom wavelengths with the estimated field intensity enhancement of up to approximately 90 is directly demonstrated using near-field microscopy. Experimental observations are concurred with electromagnetic simulations, predicting the possibility of reaching the intensity enhancements of approximately 1200 and opening thereby exciting perspectives for practical applications of CPP nanofocusing.