Digital Holographic Interferometric Measurement Of Refractive Index Gradient Distribution And Temperature Evolution Of Ktn Crystals

The potassium niobate single crystal(KTa1-x Nbx O3,abbreviated as KTN)is a solid solution of potassium niobate crystal(KNb O3)and potassium niobate(KTa O3).It has a lot of excellent performance such as the larger secondary electro-optic coefficient near the Curie temperature,and the greater light deflection effect at a lower voltage.Since the ratio of Ta/Nb ions can be controlled to change the Curie temperature into the vicinity of room temperature,it is widely used in electro-optic switches,electronically controlled scanners and other fields.Digital holographic interferometry uses charge-coupled devices to convert optical interference fringes into two-dimensional digital signals.Through digital processing,quantitative information on the microtopography of recorded images can be quantitatively obtained.It is widely used in biological scanning,military remote sensing,and environmental monitoring.etc.This thesis introduces the principle of digital holographic recording and reproduction,based on the principle of digital holographic interference,and presents the digital holographic interferometry measurement scheme and optical path of the electro-induced refractive index change of potassium niobate crystal.Subsequently,the response distribution of refractive index changes at each internal position under the condition of an applied electric field was studied in the method of digital holographic processing algorithm,and two-dimensional digital imaging was performed;The recording conditions and the factors that affect the imaging quality were analyzed by using the principle of image processing algorithm;the response of the refractive index change of the light with different polarization directions to the electric field at a fixed temperature was studied,combined with the relationship between the relative dielectric permittivity;the difference in electro-optical refractive index at each position of the crystal with doping concentration was visually demonstrated in the fixed temperature and polarization.Combined with the dielectric theory and the theory of secondary electro-optic effects,the doping concentration coefficient of each position of the crystal is inversely introduced.The influence of the doping concentration on the refractive index change performa nce of the crystal is analyzed,the crystal is studied above the crystal Curie temperature.The change of the refractive index distribution with the change of the applied electric field was esplained.The regulation of the temperature field on the electronically controlled light deflection was demonstrated intuitively;The change of the refractive index of the crystal under the Curie temperature was analyzed and discussed.