Study On Wideband Chirp Modulation Techniques Of Synthetic Aperture Ladar

Wideband chirp modulation techniques of laser are studied in this thesis. Firstly, different techniques of frequency modulation are introduced, and their advantages and disadvantages are pointed out. The principle of linear frequency modulation(LFM) based on electro-optical crystal is introduced in detail, and the reasons for the failure of achieving a wide-band chirp pulse are analyzed.A feasible experimental scheme is designed in which a microchip laser with an in-cavity electro-optical crystal is used. Numerical and experimental results show that a good linear frequency modulated laser signal can be generated by changing the modulation voltage on the crystal. Theoretical bandwidths of different kinds of electro-optic crystals are given. The analysis shows the bandwidth of the chirp pulse can be as high as 30 GHz.The measured properties of a LiNbO₃ electro-optical modulator are compared with the theoretical results, and the error between experimental data and the theoretical results has also been analyzed.