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建立了磁光晶体磁致偏振特性测试系统。该系统采用中心波长为1538nm的WGY型半导体激光器,在0～1500mT的大范围可调磁场下,对光隔离器用磁光晶体GdYBiIG样品的退偏效应进行了测试。测试结果表明,达到磁饱和或接近磁饱和时,GdYBiIG晶体的偏振性能最优;达到磁饱和后,随着磁场的增强,出现了磁致退偏效应。分析了磁致退偏效应的产生机理,给出磁致圆二向色性及磁致线双折射是产生退偏的原因。实验测试与理论分析表明,根据磁光晶体GdYBiIG这种退偏效应的规律性,在利用该类晶体制作磁光器件时,外加磁场强度稍大于它的磁饱和强度即可。
A magneto-optical crystal polarization testing system was established. The system uses a WGY-type semiconductor laser with a center wavelength of 1538nm and tests the depolarization effect of a magneto-optical GdYBiIG sample for an optical isolator under a wide range of adjustable magnetic field from 0 to 1500mT. The results show that the GdYBiIG crystal possesses the best polarization performance when the magnetic saturation is reached or close to the magnetic saturation. After magnetic saturation, the magnetic depolarization effect appears as the magnetic field increases. The mechanism of the demagnetization effect was analyzed. The reasons for demagnetization were given by the magnetochronic circular dichroism and magnetochronic birefringence. Experimental tests and theoretical analysis show that according to the regularity of the depolarization effect of the GdYBiIG magneto-optical crystal, when the magneto-optical device is manufactured by using such a crystal, the applied magnetic field strength is slightly larger than the magnetic saturation intensity thereof.