An optical modulating device, a beam steering device, and a system employing the same are provided. The optical modulating device includes an active layer, a driver configured to electrically control a refraction index of the active layer, and a nano-antenna disposed on the active layer, and having a dual nano-antenna structure including a first nano-antenna and a second nano-antenna, the first nano-antenna having a length different from a length of the second nano-antenna, and the first nano-antenna being spaced apart from the second nano-antenna. The driver includes a first driver electrically connected to the first nano-antenna, and a second driver electrically connected to the second nano-antenna.