Provided are optical modulators and devices including the optical modulators. The optical modulator may include an optical modulation layer that includes a phase change material. A first electrode may be provided on a first surface of the optical modulation layer. A second electrode may be provided on a second surface of the optical modulation layer. A first phase controlling layer may be provided, the first electrode being disposed between the first phase controlling layer and the optical modulation layer. A second phase controlling layer may be provided, the second electrode being disposed between the second phase controlling layer and the optical modulation layer. Each of the first and the second phase controlling layers may have an optical thickness corresponding to an odd multiple of λ/4, where λ is a wavelength of incident light to be modulated by the optical modulator. The optical modulator may further include at least one reflective layer. The optical modulation layer may have a thickness of about 10 nm or less. An operating voltage of the optical modulator may be about 10 V or less.