Research On Integrated Optical Electromagnetic Field Sensor

Electromagnetic field (EMF) measurement has a critical part in various scientific and technical areas. Process control, electric field monitoring in medical apparatuses, ballistic control, electromagnetic compatibility measurements, microwave-integrated circuit testing, antenna near field measurements, lightining transient electric field measurements and nuclear blast pulse electric field measurements, are some of application fields of EMF sensors. The EMF sensors based on integrated optics exhibit great advantages with respect to the electronic ones:high sensitivity, very wide bandwidth and immunity to EMF noise. In this dissertation, the characteristics of integrated optics EMF sensors are studied. The main work is provided as follows:Ⅰ. Principle and model of electric field sensor and sensing systemThe theoretical basis, fundamental parameters and structures of the electromagnetic sensor is introduced, and the sensing system is analyzed with the signal and noise componet. The antenna and optical modulator which can be used in the electromagnetic sensor is studied. Some measurement methods of the electromagnetic sensor performance are introduced according to our measurement experience, and the parameters, which will affect the minimum detetcable electric field and the linear dynamic range, are indicated.Ⅱ. Integrated optical electric field sensor with telescopic dipoleAn integrated optical elecrtric field sensor based on Mach-Zehnder interferometer with a telescopic dipole is designed and fabricated, and its electrodes are segmented and connected with a telescopic dipole. The sensor is modeled utilizing an equivalent circuit. The calculations show that the voltage gain is maximum if segmented number is seven. The fabricated device shows that the frequency response is from 10 MHz to 6 GHz, the minimum detectable electric field of 30 mV/m can be obtained, and the linear dyanamic range can reach 90 dB at 200 MHz.Ⅲ. Integrated opcial electric field sensor with tapered antennaAn integrated opcial electric field sensor with array tapered antenna is proposed, the resistance in the antenna increases from the bottom of the pattern to the tip, where a traveling wave dipole is formed. Using this pattern, the reflection current at the tip can be reduced or eliminated and the formation of standing waves can be avoided. The fabricated device shows that the minimum detectable electric field is 20 mV/m, the frequency response is from 10 kHz to 10 GHz, and the linear dynamic range with 100 dB can be obtained at 1 GHz.Ⅳ. Integrated optical magnetic field sensor with a doubly-loaded loop antennaA new type of integrated optical magnetic field sensor is proposed. The sensor consists of a LiNbO3 optical waveguide modulator and a doubly-loaded loop antenna element. Compared with the traditional magnetic field probes, it has lower disturbance to measured field, and can suppress the electrical influence effectively. The fabricated device shows that the minimum detectable magnetic field is 51.8μA/m, the frequency response is from 2 GHz to 6 GHz within±5dB, and the dynamic range can reach 98 dB at 1 GHz.Ⅴ. Integrated optical intensive electric feild sensorAn integrated optical waveguide electric field sensor with segmented electrodes is designed and fabricated. And experimental investigations of the sensor are implemented. The calibration of the sensor is taken using an impulse high voltage generator and parallel square electrodes. The maximal detectable electric field range (-75 kV/m to 245 kV/m) is obtained by analyzing the results. Finally, the measured results of a model lightning impulse electric field are given, which shows that the integrated optical electric field sensor is suitable for the investigation of lightning electric field.