Study On The Dispersion In OPCPA System

The optical parametric chirped pulse amplification (abbreviate to OPCPA) possesses the advantages of the optical parametric amplification (abbreviate to OPA) and the chirped pulse amplification (abbreviate to CPA) together, which includes the characters such as very high gain coefficient, broadband gain bandwidth, weakly thermal effect and high energy conversion coefficient. It contains three stages: stretch, amplification and compression. At present, the pulse stretch and compress switch technology is one of the successful key of the technology. Studies of dispersion usually focus on the results of only stretcher or compressor effect on pulse. In the background, making a theoretical deep research on the dispersion of OPCPA system has important meaning.In this paper, we analyze the dispersion of stretcher, compressor and materials. Include that, we concretely analyze the total process of stretch, amplification and compression. On the base of theory, we discuss the effects of misalignment of grating pair on the pulse width and temporal profile. The main achievement in the dissertation as follows:1. The influences of the original chirp and stretcher parameter on pulse width are studied. Because that the GDD of stretcher is positive, the pulse is broaden when C>0, however, the pulse firstly becomes narrow when C<0. When the groove distance of stretcher and the distance between grating and lens becomes small, the stretch multiple become large. The multiple vary with the incidence angle and wavelength of input pulse. The incidence angle always is Littrow angle.2. The influences of the dispersion originated from the mismatch of the grating pairs in the compressed stage on pulse width and temporal profile of the femto-second pulse are studied numerically. The analyses of the conditions that the planes and grooves of the grating pairs unparallel on the femto-second pulse are compared. The more severity happened in the grooves non-parallel is given by compared with the former condition. When the grating plane is misalignment, the varying of pulse width when grating G₂ revolving clockwise is more severe than that when G₂ revolving anti-clockwise. Under the condition that the grating pairs are parallel absolutely, the minimum width can be achieved by choosing the propriety power of the signal and pump light.3. The influences of misalignment of grating on the original chirp femto-second pulse are discussed. When the grating planes are unparallel, the revolving of grating and original chirp result in the pulse width varying. In the whole, the varying of pulse width when grating G₂ revolving clockwise is more severe than that when G₂ revolving anti-clockwise. The original chirp makes the pre-pulse and post-pulse weak, and changes the symmetry of pulse. When the grating grooves are unparallel, the original chirp leads to the pulse width smaller only considering GDD. However, the pulse width becomes broad considering TOD or FOD. The varying of pulse width when grating G₂ revolving clockwise is the same to that when G₂ revolving anti-clockwise. Similarly, the original chirp makes the pre-pulse and post-pulse weak, and changes the symmetry of pulse.