Dynamic Responses of Garnet-Type Optical AC Sensor Based on Faraday Effect

Linearity and error of garnet-type optical current sensor based on the Faraday effect are important parameters. In this article, an alternating current (ac) measuring method is proposed and experimentally demonstrated. The garnet and polarimeter are used as magnetically sensitive materials and detectors. The linearity and error are realized by Stokes parameters S-1 and S-2 of the P- and S-laser beams. The initial Stokes parameters S-1 of the P- and S-laser beams are adjusted to about 0.5. The experimental results show that the linearity of the (S-1) over bar and (S-2) over bar of the P-laser beam is 4.19% and 5.05%, respectively, while the linearity of the (S-1) over bar and (S-2) over bar of the S-laser beams is 48.39% and 37.84%, respectively. The measurement errors of the S-1 and S-2 of the P-laser beam are +/- 0.1% and +/- 0.035%, respectively. The measurement errors of the S-1 and S-2 of the S-laser beam are about +/- 0.32% and +/- 0.1%, respectively. The dynamic responses of the Stokes parameters of the P- and S-laser beams are consistent with ac trends and present sine variation trends. The Stokes parameter S-2 of the P-laser beam is appropriate to characterize the dynamic responses of the ac sensors. The Stokes parameter selectivity of the laser beams implies advances in designing and analyzing optical ac sensors.