Fig. 1. (a) Schematic diagram of PIC-driven metasurface device with LNOI; the red arrow is the direction of optical axis. (b) The zoomed-in scheme of the integrated metasurface is depicted with the fictitious wavefront of the waveguide modes. (c) The simulated static electric field when 1 V is applied between the electrodes, superimposed with the simulated optical field profile of the ${\mathrm{TE}}_0$ mode in the LN ridge waveguide. The black dashed lines indicate the electrodes. They have a height of 300 nm and are spaced apart by $6.5\mu \mathrm{m}$. The top width of the LN ridge waveguide is $1\mu \mathrm{m}$, and the etch depth is 210 nm.

Fig. 2. (a) The microscope image of the fabricated device. The length of the two sets of electrodes is 0.5 mm. (b) SEM image of the fabricated metasurface on the waveguide. (c) The measured intensity profile at the $x-z$ plane. (d) The measured polarization states on the Poincaré sphere of the focal spot. The blue dots on the Poincaré sphere represent the polarization states of the focal spot obtained from experimental testing. (e) Stokes parameters of one of the generated polarization state (45 deg linear polarization as shown in the inset) as a function of time. (f) Stokes parameters by switching between two generated polarization states.

Fig. 3. (a) The schematic of the switchable metasurface design. (b) SEM image of the fabricated metasurface structure. (c)–(e) Calculated results of foci under different local polarization states ψ depicted in the figures. (f)–(h) The corresponding experimental results. The polarization states are realized by applying different voltages shown in the figures to the electrodes, respectively. (i) The intensity of the right focus in (f) as a function of applied voltage. (j) Peak electro-optic amplitude for modulation frequencies up to 2 GHz (Video 1, MP4, 120 KB [URL: https://doi.org/10.1117/1.AP.6.1.016005.s1]).

Fig. 4. (a)–(c) Calculated results of switchable focal length under different local polarization states depicted in the figures. (d)–(f) The corresponding experimental results were realized by applying different voltages to the electrodes as shown in the figures, respectively. (g)–(i) Calculated results of switchable OAM beams with switchable topological charges under different local polarization states depicted in the figures. (j)–(l) The corresponding experimental results were realized by applying different voltages to the electrodes as shown in the figures, respectively.

Fig. 5. (a) The simulated intensity and (b) phase of the scattered light when the rectangular nanostructure’s length and width vary from 100 to 500 nm. (c) SEM image of the fabricated metasurface for Bessel beams. (d)–(f) Calculated results of switchable Bessel beams under different local polarization states depicted in the figures. (g)–(i) The corresponding experimental results by adjusting voltages applied to the electrodes, respectively. (j)–(l) The corresponding cross-sectional images along the white dashed lines in (g)–(i), respectively.