基于偏硼酸钡晶体的电光补偿型光学磁场传感器

An optical magnetic field sensor based on electro-optic compensation and beta-barium borate (β-BaB₂O₄,BBO) crystal is proposed and experimentally demonstrated.The proposed optical magnetic field sensing unit is mainly composed of single BBO crystal and two polarizers.By means of light intensity modulation,the sensing light intensity variation caused by the measurand magnetic field and Faraday effect can be timely compensated by the applied voltage and electro-optic modulation.Under the condition that the sensing light intensity is compensated and kept to be constant,the measurement of magnetic field can be conducted by measuring the electrooptic compensation voltage.The 50 Hz ac magnetic flux density has been measured in the range of 167 Gs by use of a block of BBO crystal with dimensions of 4 mm×4 mm×20 mm.The compensation voltage can be decreased by choosing a proper deviation angle between the probing light beam and the principal optical axis of the BBO crystal,e.g.,0.76°.In this case,a typical electrooptic compensating voltage is about ~0.018 3 V•Gs^-1,which is approximately 30 times lower than the experimental result previously reported.Main advantages of the proposed magnetic field sensor include better insulating ability,lower disturbance to the measurand magnetic field,broader dynamic measurement range,and potential closed-loop measurement of magnetic field.