An optical apparatus may comprise: an electrically reconfigurable optical layer comprising at least one phase-change material, wherein an optical property of the phase-change material is reconfigurable by an electric field; an optically transparent top electrode and a bottom electrode, the top and bottom electrodes configured to apply the electric field to the electrically reconfigurable optical layer, wherein the electrically reconfigurable optical layer is disposed between the optically transparent top electrode and the bottom electrode; and a colossal-K dielectric layer disposed between the electrically reconfigurable optical layer and the bottom electrode. The phase-change material of the electrically reconfigurable optical layer may comprise phase-change nickelate or tungsten oxide. The phase-change material of the electrically reconfigurable optical layer may have a perovskite structure. The phase-change nickelate or tungsten oxide may enable to actuate large refractive index changes of more than 1 in infrared wavelength spectrums at high speeds of phase reconfiguration of more than 1 kHz by applying the electric field to the phase-change material.
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