Asymptotic stability of laser-driven lightsails: Orders of magnitude enhancement by optical dispersion engineering in gratings

TL;DR

This paper demonstrates that optical dispersion engineering in gratings can significantly enhance the asymptotic stability of laser-driven lightsails, enabling better control through relativistic optical forces.

Contribution

It introduces a method to achieve full asymptotic stability of nanophotonic sails using optimized dispersion properties, surpassing traditional mirror designs.

Findings

Damping of unstable degrees of freedom can be enhanced by orders of magnitude.

Relativistic optical forces can provide comprehensive control over lightsail motion.

Full asymptotic stability is achievable through dispersion-engineered gratings.

Abstract

Lightsails are promising spacecraft that can traverse interstellar distances within decades via radiation-pressure propulsion from high-power lasers. The envisioned missions crucially rely on the sail being confined within the propelling laser beam, requiring restoring and damping mechanisms for both translational and rotational degrees of freedom. Here, we use a two-dimensional rigid model to show that full asymptotic stability of planar nanophotonic sails can be achieved through purely optical, relativistic forces and torques, which damp all unstable degrees of freedom. By judiciously optimizing the angular and frequency dispersion of diffraction gratings, we find that damping can be enhanced by orders of magnitude compared to plane-mirror sails. Therefore, relativistic effects can, in principle, provide comprehensive and realistic control over lightsail motion.