Fundamental study of optical probe current sensor using Kerr effect of single magnetic domain film

An optical probe current sensor using a Kerr effect of an Fe-Si/Mn-Ir exchange-coupled film has been investigated. The optical sensing technique has the advantage of no induced noise from the external electromagnetic interference. In addition, since the proposed method using the Kerr effect of single domain exchange-coupled magnetic thin film utilizes only magnetization rotation, the Barkhausen noise due to a domain wall pinning can be excluded. A fabricated optical probe current sensor consisting of He-Ne laser, Fe-Si/Mn-Ir exchange-coupled film, beam splitter, pin-PD and differential amplifier, exhibited a current sensing bandwidth of 10 kHz and a sensitivity of 2.26 V/A. By using the fabricated optical probe current sensor, the current sensing for PWM inverter motor has been demonstrated.