An optical unidirectional device tunable by a magnetic field

A tunable optical unidirectional device or optical isolator composed of a metal subwavelength grating covered with magneto-optical rotation medium is proposed. The results of a simulation show that the difference of transmissivity in opposite directions varies from 0 to 83% with an external magnetic field at room temperature. The largest field needed to control transmissivity is only 1.1 T, so the working conditions can be easily achieved. A theoretical method to calculate transmissivity is presented and the unique transmission characteristics of this new device are explained satisfactorily.