Figure 2: A far-field nanoscope.
(a) An elliptical reflector (x-, y- and z-radii of 20, 20 and 8 μm, respectively) is placed surrounding a pair of ellipsoidal metal dimers (x-, y- and z-radii of 1.25, 1.25 and 0.25 μm, respectively), forming an imaging system. The ellipsoid dimer was chosen for fewer requirements on computation resources than spherical dimer. The frequency of the light corresponds to 500 nm in vacuum. The centre of the dimer is coincident with one focus of the elliptical reflector. An image plate is placed at the other focus of the elliptical reflector. A point source is placed at the centre of the gap. Its image is shown in b. As we move the source horizontally by 8 and 24 nm from the centre, the corresponding images show resolvable movement (c,d). The corresponding cross-section plots are shown in e through g. The magnification is plotted in h as DX versus dx curve. This calibration is fairly linear within ∼12 nm (red dashed curve). A second order curve (black curve) shows a better fit. (i) The resolution depends on the size of the gap. We fix a point source at 8 nm, sweep the gap, and plot the displacement of the image in i. A 1/x curve describes the DX versus gap relation well, black dash line in i.
