Study On Controllable Frequency Doubling Modulation And Deflection Properties Of Lithium Niobate Crystal

With the rapid development of the information age,especially the rapid popularization of the Internet,the traditional electronic communication system has been gradually difficult to meet the needs of people.To solve this problem,the optical communication technology has been developed unprecedentedly.Optical modulation and deflection technology are the core technologies in optical communication.The means and materials to realize optical modulation and deflection are constantly innovated and researched.Electro-optic materials stand out because of their high response rate and stability.Modulators and deflection devices based on electro-optic materials have developed rapidly.Various electro-optical materials have been studied,such as potassium tantalum niobate crystal potassium dihydrogen phosphate crystal and lithium niobate crystal.LiNbO₃ crystal is a kind of ABO₃ perovskite material with various optical properties,such as ferroelectric,piezoelectric,acousto-optic,photorefractive,electro-optic,nonlinearity.It is an artificial crystal with the most comprehensive optical properties and the best indexes found so far,and its growth process is relatively mature.This kind of crystal with excellent performance and low growth cost should exert its excellent performance in the field of beam modulation and deflection.In this paper,lithium niobate is used to realize frequency doubling,then high response rate and low cost modulation and deflection of frequency doubling light are performed.For this purpose,this paper conducts the following research:Firstly,the frequency doubling performance of lithium niobate crystal is tested,by measuring its Maker fringes,which is the relationship between the incident angle of pump beam and the intensity of the second harmonic wave.The Maker fringes of crystals with different light length and different rotation axes were measured,and the most suitable crystal for the modulation and deflection operation was selected for the next experiment.Then,the influence of the electric field intensity on the crystal frequency doubling intensity is theoretically analyzed,and the corresponding electro-optic modulator is designed.According to the theoretical results,the precise and stable electrically controlled frequency doubling light intensity modulation with high extinction ratio is realized,which can be used to make a new type of optical switch.Moreover,according to the performance results of the modulator,a method of measuring electro-optic coefficient is proposed.And a temperature control device is set up to realize the frequency-doubling light intensity modulation of temperature control with the same principle.The temperature control modulation can realize the modulation in a large range with only a small temperature difference,thus realizing a kind of optical modulation with very low energy consumption.Finally,based on the previous results of optical modulation,by designing the incident angle and divergence angle of the light,the frequency doubling spot deflection can be controlled by uniform electric field or temperature field,and the beam deflection angle is in good agreement with the theoretical analysis results.The deflection driven by electric field has the advantages of faster response speed and higher stability and accuracy,while the deflection driven by temperature field can achieve considerable beam angle deflection with only low energy,and each of them has its own advantages.And,both electric field and temperature field,comparing with the beam deflection field commonly used theory of space charge injection and compositional gradient theory,does not need to build complex gradient field,has low processing cost,and easier to use.By using lithium niobate crystal,this paper implements a stable and controllable deflection beam modulation method.This method by changing the frequency doubling light intensity and exit angle to obtain the corresponding light signal which is modulated,can provide new technology in optical communication field.And it has a certain significance for promoting the development of optical modulation and deflection field.