Fig. 1
Schematic diagram of the semicircular slit plasmonic lens (a) and the spin-independent SPP lens consisted of two semicircular slits (c). With the illumination of LCP and RCP light, the excited SPPs will experience spin-dependent spiral phases (b). Adding another semicircular slit can introduce an extra spiral phase, and the two spiral phases can cancel out each other when r1 − r2 = λsp/2 (d)