Figure 4

Magnetic in (a) and electric in (b) relative shifts of the resonance wavelength of the CL7 fundamental mode as a function of the BNA-to-CL7 distance d. Three different BNA-on-tip apex radius are considered (R = 180 nm in black, R = 250 nm in red and R = 500 nm in blue). The magnetic shift induced by an apertureless SNOM tip with radius R = 250 nm is also presented in green line in (a).