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 I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> on the target arrives when the beam power P = P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">opt</sub> (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">opt</sub> is called the optimal beam power), and the intensity on the target will decrease as the beam power P increases further when P > P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">opt</sub> . The P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">opt</sub> of nanosecond and picosecond pulsed beams is lower than that of femtosecond pulsed beams, while the maximum intensity I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> on the target of nanosecond and picosecond pulsed beams is higher than that of femtosecond pulsed beams. The P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">opt</sub> and I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> 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.
Highlights
The beam quality of high-power pulsed laser beams propagating from the ground through the nonlinear and dispersive atmosphere to space orbits is important for laser ablation propulsion’s applications in space, such as space-debris removal, launching small probes into Low Earth Orbit, etc. [1]–[4]
Our group demonstrated that the uniform irradiation may be generated by self-focusing in the inhomogeneous atmosphere [15], derived the analytical formula of the modified focal length of the lens to move the actual focus of partially coherent beams (PCBs) to the debris target [16], and derived the analytical propagation formulae of PCBs propagating in the turbulent atmosphere by using the thin window” (TW) model and the quadratic approximation of nonlinear phase shift [17]
We showed that the temporal pulse splitting may appear on the space debris because of group-velocity dispersion (GVD) and Kerr self-focusing effects, and derived the formula of M2-factor [21]
Summary
The beam quality of high-power pulsed laser beams propagating from the ground through the nonlinear and dispersive atmosphere to space orbits is important for laser ablation propulsion’s applications in space, such as space-debris removal, launching small probes into Low Earth Orbit, etc. [1]–[4]. Our group demonstrated that the uniform irradiation may be generated by self-focusing in the inhomogeneous atmosphere [15], derived the analytical formula of the modified focal length of the lens to move the actual focus of partially coherent beams (PCBs) to the debris target [16], and derived the analytical propagation formulae of PCBs propagating in the turbulent atmosphere by using the TW model and the quadratic approximation of nonlinear phase shift [17] These studies are restricted to continuous wave (CW) laser beams [5], [12]–[17]. The principal features of Kerr self-focusing, GVD and diffraction are considered, and the beam quality of high-power annular pulsed laser beams propagating from the ground through the nonlinear and dispersive atmosphere to space orbits are studied, including the spatiotemporal coupling, the optimal beam power, the B integral and the Strehl ratio. The main results obtained in this paper are explained in physics
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