An Optical Magnetic Field Sensor With Improved Sensitivity Based on Multiloop Antenna Loaded With LiNbO₃ Crystal

Based on the Pockels effect of lithium niobate (LiNbO3) crystal, a resonant magnetic field sensor with multiloop antenna and segmented modulation electrode loaded with LiNbO3 has been designed, fabricated, and experimentally demonstrated. The resonant multiloop antenna and the segmented modulation electrode structure are used to enhance the magnetic field induced voltage, thereby enhancing the electrooptic (EO) modulation and improving the sensitivity of the sensor. By twisting the 1/2 beat length polarization-maintaining fiber (PMF) at the front end of the input PMF collimator 90° to ensure that the sensor has a static operating point of
$\pi $
/2, so that it can operate in the near linear region. The experimental results indicate that when the input magnetic field frequency is 500 MHz, there is a linear relationship between the input and output of the sensor, And the minimum and maximum detectable magnetic fields are 36.72 and 181.12 dB
$\mu \text{A}$
/m respectively, resulting in a linear dynamic range (LDR) of approximately 144 dB. The sensitivity of the sensor is 0.974 dBm/(dB
$\mu \text{A}$
/m), and the linear correlation coefficient is 0.99825. All these results indicate that the developed sensor has the advantages of higher sensitivity and LDR, which is suitable for electromagnetic compatibility (EMC) measurement.