Tip-enhanced Raman spectroscopy based on plasmonic lens excitation and experimental detection.

A tip-enhanced Raman spectroscopy (TERS) based on plasmonic lens (PL) excitation is proposed in this work. A PL expected to realize a strong longitudinal electric field focus is designed. The focusing performance of the PL is calculated via finite-difference time-domain (FDTD) simulation and experimentally detected by a scattering-type scanning near-field optical microscope. The PL is introduced to a TERS system as a focusing device. Experimental results with carbon nanotube samples indicate that the Raman scatting signal is significantly enhanced. It proves experimentally that the combination of a PL focused excitation field with a metallic tip in a TERS system is a promising method.