Philip H. Jones, Onofrio M. Maragò & Giovanni Volpe
Fig. 11.3 — Gratings and Fresnel lenses
A single focal spot can be generated in the front focal plane of a lens by a phase modulation corresponding to a grating and/or a Fresnel lens: (a) grating along x; (b) grating along y; (c) combination of gratings along x and y; (d) positive Fresnel lens; (e) negative Fresnel lens; (f ) combination of the grating in (c) and Fresnel lens in (d). Both the phase modulation (top) and the focal spot intensity (bottom) are shown.