Tunable wide-band graphene plasmonic nano-color-sorter: application in scanning near-field optical microscopy

Tunability of the Fermi level of graphene is exploited to implement a plasmonic nano-color-sorter for scanning near-field optical microscope (SNOM) applications capable of handling large tip sample couplings. Nano-color-sorting has been used in SNOM through creating multiple spatially separated hot spots for different incident wavelengths. We show that in the presence of high-refractive-index samples an unwanted redshift in the spectral response of the dual-color probe occurs. This limitation can be compensated for using graphene and adjusting its chemical potential to obtain a blueshift in probe spectral response. The Method of Moments analysis technique is employed to engineer the probe numerically. This probe is tuned to work at standard Nd:YAG laser lines (1054 and 1319 nm) and achieve sub-wavelength resolution as small as 0.002 lambda(2). (C) 2019 Optical Society of America