Research On Total Ionizing Dose Effect On The Performance Of LiNbO₃ Intensity Modulator

With the increasing demand for data capacity and transmission speed,traditional microwave communication has been unable to meet human needs.Based on the unique advantages of optical signals,free space optical communication achieves the advantages of high modulation rate,wide bandwidth,and less spectrum resources.It is recognized as the next generation communication technology to replace the microwave communication.Electro-optic modulator is one of the most widely used optoelectronic devices in free space optical communication system.Its excellent performance directly determines the working state of the entire optical communication system.LiNbO₃ intensity modulator,as the most widely used electro-optic modulator at present,is subject to the harsh space environment.However its service life and working stability often restrict the electro-optic modulator.Therefore,in recent years,some researchers have studied and predicted the radiation effect of LiNbO₃ intensity modulator through ground radiation simulation experiments.In the experiments,the total dose in space environment is usually simulated by high dose rate to accelerate the radiation test.The radiation effects in the space environment are discussed and compared with the radiation simulation experiments on the ground.The radiation dose rate which is closest to the space radiation is selected,and the effect of total ionizing dose on lithium niobate electro-optic intensity modulator is studied by time accumulation.The influence mechanism of total dose radiation effect on lithium niobate intensity modulator is analyzed theoretically.The influence of total dose effect on the half-wave voltage of lithium niobate intensity modulator is further predicted theoretically through the influence of radiation on the refractive index of lithium niobate crystal.From the ionization effect of radiation effect on lithium niobate crystal,the mechanism of total dose effect on insertion loss and extinction ratio of lithium niobate intensity modulator are deduced.The ground simulated space radiation experiment of lithium niobate intensity modulator was carried out.With the radiation dose rate at10 mrad/s,the experiment lasts for 40 days.The half-wave voltage,insertion loss and extinction ratio of lithium niobate intensity modulator under different total radiation doses were measured during the experiment.The mechanism of the effect of total radiation dose on LiNbO₃ intensity modulator is discussed through the combination of experiment and theory.In this paper,the influence mechanism of radiation effect on electro-optic crystals such as lithium niobate is proposed.And the results are analyzed in combination with the engineering parameters of the devices and the radiation dose.The experimental results verify the conclusions,which provide a certain reference value for the future research on the radiation of electro-optic crystals.