Nondestructive Testing Technique for Defect Detection in LiNbO3 Using Infrared Thermal Imaging Camera

The existence of defects in lithium niobate (LiNbO 3 ) degrades the specific properties required of LiNbO 3 as substrate material, which is a major problem inhibiting device constructions. For the purpose of providing a convenient and quick tool for use in a nondestructive testing technique for defect detection, the feasibility of using an infrared thermal imaging camera (IR camera) is examined by comparing the results of IR camera use with those of two methods, scanning laser microscopy (SLM) and light scattering tomography (LST). We have succeeded in the detection of defects in the LiNbO 3 substrate by observing the thermal properties of defects in a relatively wide field of view ($8\times 6$ mm 2 ) compared with the case of using conventional microscopes. The maximum temperature difference of the defects in the LiNbO 3 substrate was 0.47 K.