Laser Cooling Assisted Thermal Management of Lightsails
Weiliang Jin, Wei Li, Chinmay Khandekar, Meir Orenstein, Shanhui Fan
Abstract
A lightsail can be accelerated to relativistic speed by the radiation pressure of a laser having an intensity of the order of GW/m2. Such an extreme light intensity presents a critical challenge in the thermal management of lightsails. In this Article, we propose to use solid-state laser cooling for dissipating heat from such a lightsail. Our approach uses the same laser that is accelerating the sail and can be used in addition to the previously explored radiative cooling. With our approach, we show that the cooling rate of a sail composed of a micron-thick layer doped with ytterbium ions can exceed that of blackbody thermal emission. This allows illumination by higher intensity lasers and, consequently, shortens the acceleration distance to reach relativistic speed. Due to the Doppler shift, the performance of our approach is impacted by the limited bandwidth of the laser cooling dopant. When a constant-frequency pumping laser is used, laser cooling is particularly helpful for target velocities ≲0.05c for room-temperature operations.