Study On Miniature Electric Field Sensor Based On Electro-optic Materials

With the development of miniaturized and highly integrated 5G chip technology,the physical size of the internal components of the chip is getting smaller and smaller,and the internal integration as well as the operating frequency is increasing,leading to the increasingly prominent electromagnetic interference（EMI）phenomenon among the chip components.The use of high-resolution,high-fidelity electric field sensors provides an important means for EMI and electromagnetic compatibility（EMC）testing of chips.A good local electromagnetic shielding material is one of the effective solutions to EMI.What hinders the use of this method is the current lack of high-resolution and high-fidelity electric field sensors for measurement and evaluation of good shielding materials.Therefore,the need for developing new miniature electric field sensors for chip failure localization and analysis is extremely urgent.For chip failure location and analysis,the traditional solution is to use a metal probe with resonant antenna structure to scan the electromagnetic radiation,however,the electric field sensor with metal material will couple with the original field to be measured and interfere with the distribution of the original field measurement,resulting in low fidelity of the measurement.Moreover,electric field sensors containing metallic elements often have narrow-band measurement characteristics.Therefore,to address the above problems,this thesis investigates the miniature optical electric field sensor with full dielectric based on the linear electro-optic effect of electro-optic materials.The main work of this thesis is divided into two parts:simulation and experiment.The first part is to simulate and design microstructured electric field sensors with optical localization capability using different electro-optic materials,and analyze the performance parameters of the sensors through numerical simulations,which involve electro-optic materials such as lithium niobate（Li Nb O₃）,barium titanate（Ba Ti O₃）,PMN-PT(（1-x）Pb(Mg_1/3Nb_2/3)O₃-x Pb Ti O₃,（1-x）PMN-x PT).On the one hand,an optical resonance cavity with optical localization capability is designed using microstructures to improve the effective electro-optic coefficient,thus increasing the sensitivity of the sensor.On the other hand,the electro-optic material-based electric field sensor has the advantage of high fidelity and broadband measurement because it is designed as a fully dielectric type.The microstructure simulation method uses the finite time domain difference（FDTD）method to investigate parameters such as the optical transmission spectrum,the enhanced optical localization capability enhancement factor f_opt,the sensitivity of the resonance-based electric field sensor S and the minimum detectable electric field E_min.The simulation calculation results show that the PMN-PT designed miniature electric field sensor has the best performance with the quality factor Q close to 1×10⁴,the sensitivity can reach 4.774 pm/（V/m）,and the minimum measurable electric field field strength can be as low as 20 m V/m.The second part is the electric field sensing experiment using electro-optic materials.Due to the limitation of laboratory processing equipment and time,the corresponding block or thin film crystals combined with optical polarization state modulation are used in the experimental part of this paper for electric field measurement.The principle of electric field sensing measurements is mainly based on the modulation of the polarization state of light passing through the electro-optic crystal in the presence of an electric field.By demodulation detection of the optical polarization state,the weak polarization state change information can be converted into a detectable light intensity signal.A transverse electromagnetic wave box is used to generate a uniform electric field in the experiment,and the demodulation of the optical signal is detected by a lock-in amplifier.The electric field sensing measurements were performed by using a total of four samples:block Li Nb O₃,thin film Li Nb O₃,PMN-PT block crystals and Ba Ti O₃ nanoparticles spin-coated on slides.The experiments show that the minimum detectable electric field reaches 30.23 V/m for the samples made by using barium titanate nanoparticles spin-coated on slides;12.78 V/m for the lithium niobate blocks with 0.5 mm thickness,and 47.91 V/m for the samples with 200 nm lithium niobate films on quartz crystal substrates;Using 1mm thickness of 0.67PMN-0.33PT sample,the minimum detectable electric field reaches 150m V/m.Summarizing the above different pieces,PMN-PT has the smallest detectable electric field;barium titanate nanoparticles have the advantage of simple preparation and processing;and lithium niobate thin film samples on quartz crystal substrate have the smallest longitudinal resolution of 200 nm.The innovation points of this paper are mainly:Propose a new electro-optical material-based all-dielectric electric field sensor,combined with Fano resonance so that the light localization in the microcavity to enhance the effective electro-optic coefficient,sensitivity and spatial resolution to produce a corresponding increase in the minimum detectable electric field to m V/m level.