Fig. 4. Simulated full-width at half maximum (FWHM) for the designed tunable metalens with varying applied voltages. FWHM for the incident wavelength of (a) 488 nm with an applied voltage of −8.9 V (b) 532 nm with an applied voltage of −16.6 V. (c) 633 nm with an applied voltage of −33.7 V. (d) FWHM for each incident wavelength of 488 nm, 532 nm, and 633 nm under each applied voltages of −8.9, −16.6, and 33.7, respectively.