Fig. 1.

Principle of a UV metasurface for sculpturing optical focus. (a) and (f) Schematic diagrams of focusing photoacoustic illumination without and with a UV metasurface, respectively. (b) A clear back aperture of an objective by positioning a glass substrate that produces an optical diffraction-limited light field (c). (d) Light intensity distribution along the optical axis of the focus spot. (e) Measured height profile of the glass substrate that is positioned before the objective when performing the traditional PAM imaging. (g) Phase pattern of the UV metasurface in which the phase is π and 0 in the black and white regions, respectively. (h) An extended DOF by assigning the UV metasurface onto the objective’s back aperture. (i) Light intensity distribution along the optical axis. (j) Measured height profiles of the UV metasurface producing the predesigned phase distribution in (g). UVM: UV metasurface.