Figure 4. The intensity distribution along x direction in the focal plane (a) and along the optical z-axis (b), where the etch depth of 400 nm is kept invariable. The solid and dot curves respond to the cases of light incident from the FZP’s substrate and structure sides, respectively, and all intensity normalized to the intensity of the incident light

From

The Focusing Characteristics on the Binary Phase Sub-wavelength Fresnel Zone Plate

Taikei Suyama

International Journal of Physics. 2019, 7(3), 86-90 doi:10.12691/ijp-7-3-3