(a), (b) Phase singularity locations at five different transverse planes and isolated Hopf link and Trefoil knot configured from the phase distributions measured by the scanning method. Insets: Top views of the topological configurations. The measured diameters of these configurations are about 660 μm, the longitudinal lengths are about 10 cm. (c), (d) Isolated Hopf link and Trefoil knot configured from numerical calculation.