Magnetic pulse generation for high-speed magneto-optic switching

In this article, the magnetic pulse characteristics needed to achieve high-speed magneto-optic (MO) switching are investigated. A fiber-based, MO, low-voltage optical switch capable of 200 ns switching is presented, along with the special circuit characteristics for magnetic field generation for high-speed switching. The switch consists of the optical system, the MO material (bismuth substituted iron garnet [(Bi1.1Tb1.9)(Fe4.25Ga0.75)O-12]), and a high-speed magnetic field driving circuit. A Faraday rotator is placed within the interferometric loop of a fiber-optic Sagnac interferometer, and interference at the output ports is controlled by the applied field. The fast switching speed is accomplished via the special design of the magnetic pulse generation circuitry. The applied magnetic field overshoots the field necessary to achieve the desired Faraday rotation and then settles to a steady state field. If the duration of the overshoot is less than the time it takes the material to saturate, a fast optical switching time can be achieved without saturating the material. The effects of the overshoot amplitude and duration and steady-state amplitude on optical rise time (determined by domain wall velocity) are studied and experimental results are presented. (C) 2011 American Institute of Physics. [doi:10.1063/1.3549632]