Analysis of the damage mechanism of gray point induced by 800 nm femtosecond laser pulse on IT-CCD camera

As located in the focal plane of the imaging system, the image sensor will be easily influenced by the huge optical gain, which is brought in the image sensor by the external optical system and microlens on the surface of the device. Laser has a great influence on the image sensor, which is a sensitive link of the anti-laser reinforcement of the imaging system. Improving the performance in extreme light conditions in order to study the vulnerability of image has an important significance of reinforcement. As a typical visible light image sensor, which has advantages of sensitivity, high dynamic, small, light and so on, IT-CCD has been widely used in the fields of reconnaissance, detection and military. An 800nm femtosecond pulse laser was used to carry out experimental research on the laser irradiation effect of IT-CCD. The results shown that the local pixel of IT-CCD was in a state between undamaged and the white point damaged after irradiating by the laser, which was named by gray point. It was shown that the influenced pixels of IT CCD were changed by the laser, but no obvious deformation occurred. Through microscopic detection and analysis, the damage mechanism was expounded, further analysis was done. With focus ion beam (FIB) technique, it was found that there was photosensitive potential well, micro-structure of SiNx filling layer under microlens of the IT-CCD. When the gray point damage occurred, neither the photosensitive potential well at the bottom of the device was damaged, nor was the microlens structure on the surface. It turned out that the SiNx filling layer was influenced by the laser. Through elucidating the mechanism of this damage of the gray point, it lays a foundation for damage mechanism research.