It provides an optical body that can be optionally and quickly control the incoming light of the optical characteristics.
Thereby the side-by-side the first reflection layer 3 and the second reflection layer (5) a refractive index-variable layer 8 and the magneto-optical material formed of a garnet, such as layer (9) made of PLZT or the like between. When this linearly polarized light is incident toward the first reflective layer 3, the incident light to interfere with the magneto-optical material layer (9) is converted to right-handed circularly polarized light and left circularly polarized light. Amount of light, the slight phase difference, but the phase difference and the amplification between the pair of the reflective layer (3, 5) when the multiple reflection is also controlled according to the refractive index of the refractive index control variable layer 8.
To do this by the phase difference is back to interfere with the controlled amplifying the left and right-handed circularly-polarized light to the magneto-optical material layer (9) and return it to the linearly polarized light, the polarization plane is rotated according to the phase difference.