Fig. 1. Schematic diagram of concept of novel zone plate, showing (a) classic FZP, (b) linear FZP, and (c) its simulation results, (d) ring focal zone plate, (e) one-dimensional structure, and (f) its simulation results.

Fig. 2. Structures of ring focal zone plates with different values of d.

Fig. 3. Energy distributions and intensity profiles of ring focus with different values of d.

Fig. 4. (a) Energy distribution and (b) intensity profiles of ring focus for three different wavelengths.

Fig. 5. Wavelength-dependent normalized intensity of micro-focus.