Laser cooling assisted thermal management of lightsails

TL;DR

This paper investigates laser cooling as a thermal management strategy for lightsails, demonstrating its potential to handle high laser intensities and improve acceleration efficiency within certain velocity limits.

Contribution

It introduces the application of solid-state laser cooling to lightsails, showing it can surpass blackbody emission and enable higher laser intensities during acceleration.

Findings

Laser cooling rate can exceed blackbody emission in doped layers.

Laser cooling is effective for target velocities up to ~5%.

Enhanced thermal management allows for shorter acceleration distances.

Abstract

A lightsail can be accelerated to ultra-high speed by the radiation pressure of a laser having an intensity of the order of GW/m$^2$, which though presents a critical challenge in the thermal management of lightsails. In this letter, we explore the applicable regimes of solid-state laser cooling in dissipating heat in additional to the previously explored radiative cooling approach. We begin by examining the cooling capacity of laser cooling, and show that the cooling rate from a micron-thick layer doped with ytterbium ions can exceed that of blackbody thermal emission. This allows more intense laser illumination upon material damage, and consequently shortened acceleration distance. Next, we explore the impact of the limited operating bandwidth of laser cooling to account for the Doppler shift of the pumping laser, and conclude that laser cooling is helpful for target velocities $\lesssim5\%$ for room-temperature operations.