We propose a design and numerical study of an optically tunable metamaterial based on an electric-field-coupled inductor-capacitor resonator variant in the terahertz regime. In contrast to earlier proposed structures, we demonstrate that a blueshift of the resonance frequency under illumination can be accomplished with realistic material parameters and a broadband tuning range on the order of 40% has been demonstrated, which is found to be based on a photoconductivity-induced mode-switching effect. We also present a variant of this structure, which simultaneously possesses two resonance frequencies and can be used as an optically switchable dual-band resonator. Our all-optical modulators and switches may offer a step forward in filling the ``THz gap.''