The Research On Photodetector Performance Influenced By Femtosecond Laser Pulses

Filament can be generated when femtosecond laser pulses transmit in air. Following the appearance of filament, the phenomenon of supercontinuum spectrum broadening will generate along the direction of laser propagation. This unique atmospheric propagation property has aroused widespread concern in the field of optoelectronics.In this thesis, the research status of filament supercontinuum formation in air using femtosecond laser pulse and CCD irradiation by laser at home and abroad is introduced at first. The theoretical mechanism of spectrum broadening in self-focusing and defocusing, self-phase modulation, four-wave mixing, and plasma radiation during the process of filament formation is elaborate theoretically. Then, the basic structure and the principle of CCD imaging and the determination method of saturation threshold for laser irradiation CCD are introduced. Finally, the real-time interference research on the visible area array CCD imaging system using femtosecond laser pulse and the generated filament is presented. The main contents include as follows:1. Irradiate the visible-light array CCD using femtosecond laser at the repetition rate of10Hz and1kHz, finding that the interference effect using1kHz femtosecond laser was better through the comparison of the experimental results. It was because high repetition rate laser could irradiate each frame of video images which is scanned out by CCD.2. Research on the real-time interference with the visible area array CCD in real-time using1kHz femtosecond laser, the filament supercontinuum radiation, and the supercontinuum filtered fundamental frequency laser, respectively. Linear state, single point saturation, discontinuous point crosstalk, vertical bright line and some other interference phenomena are observed, and the saturation thresholds using three different spectral components of the light source are obtained. The reasons for different saturation thresholds are analyzed contrastively and the mechanism of the interference phenomenon is explained.3. Study on the spatial resolution of the interference for saturation thresholds of CCD using the plasma supercontinuum radiation generated by femtosecond laser. The results show that the interference effect is good within the area of visible area array CCD covered by the supercontinuum spot.