An optically controlled isolator using ferrite edge mode

This paper introduces a new type of microwave isolator. The nonreciprocity of the isolator can be optically controlled. The operation is based on the two phenomena: the ferrite edge-mode and the photo-generated plasma on silicon substrate. Conventional ferrite edge-mode isolator has been made of the ferrite and the resistive material. The later is used to absorb the reverse-propagating wave of the isolator. An inadequate choice of the resistive body leads to the imperfect absorption; the isolation ratio decreases. In this paper, a novel isolator is introduced by using this change of isolation. The optical control is realized by changing the intensity of illumination to produce the variation of the plasma density on the silicon substrate. On the isolator, the frequency response is investigated both experimentally and numerically. The numerical analysis is performed by the FDTD method. Both numerical and experimental results have shown that the isolation ratio can be controlled for 39 dB at 11GHz by the laser-illumination on the silicon substrate.