Annular Pump-Based OPCPA for Vortex Pulses Amplification

We proposed and numerically studied an optical parametric chirped amplification (OPCPA) scheme for amplification of ultrashort vortex pulses using annular pump beams. Compared to the scheme using super-Gaussian pump beams, the annular pump beam can provide better spatial overlap with the vortex beam, enhancing energy conversion efficiency while preserving the annular intensity distribution of the vortex beam. Numerical simulation results demonstrate advantages of the annular pump scheme over the super-Gaussian pump scheme. Firstly, the annular pump scheme significantly reduces the shift of the helical phase singularity while better maintaining the intensity symmetry of the signal beam along the walk-off direction. Secondly, it achieves higher energy conversion efficiency. Finally, under the condition that the total pump energy input is equal, the annular scheme produces a broader output signal spectral bandwidth compared to the super-Gaussian scheme. Furthermore, the impact of noncollinear angle on vortex purity, as well as the effects of intensity distribution distortion and wavefront phase distortion of both the signal and pump beams on the performance of the annular pump scheme, were analyzed in detail. We hope these results can provide novel insights and references for the design of ultrashort vortex pulse optical parametric amplification systems.