Beam Quality of Annular Pulsed Laser Beams Propagating Through the Nonlinear and Dispersive Atmosphere

Abstract

The Kerr self-focusing and group-velocity dispersion (GVD) effects play important roles when a high-power pulsed laser beam propagates from the ground through the nonlinear and dispersive atmosphere to space orbits. For an annular pulsed laser beam, the Kerr self-focusing and GVD effects on the beam quality on the target is studied in this paper. Due to self-focusing, the maximum intensity Imax on the target arrives when the beam power P = Popt (Popt is called the optimal beam power), and the intensity on the target will decrease as the beam power P increases further when P > Popt. The Popt of nanosecond and picosecond pulsed beams is lower than that of femtosecond pulsed beams, while the maximum intensity Imax on the target of nanosecond and picosecond pulsed beams is higher than that of femtosecond pulsed beams. The Popt and Imax of annular pulsed beams are higher than those of Gaussian pulsed beams. In addition, the B integral and the Strehl ratio are also adopted to describe the beam quality on the target. On the other hand, because of the interplay of Kerr self-focusing and GVD effects, the temporal pulse splitting and self-healing may take place on propagation, and the temporal pulse splitting may take place more than once. The results obtained in this paper are useful for laser ablation propulsion's applications in space.

Keywords

• Laser beam propagation
• atmosphere
• Kerr self-focusing
• group-velocity dispersion (GVD)
• beam quality