Caltech is spearheading efforts to develop lightsail technology, which aims to enable spacecraft to travel faster than any previous missions, potentially opening new frontiers in interstellar exploration. Harry Atwater, the Otis Booth Leadership Chair of Caltech's Division of Engineering and Applied Science, emphasizes that this technology could facilitate direct spacecraft exploration of distant cosmic regions, previously accessible only through remote observation.
Atwater and his team have created a testing platform to analyze ultrathin membranes that could serve as lightsails. This platform measures the force exerted by lasers on these sails, marking a pivotal step from theoretical designs to practical applications in space travel. The researchers face challenges in developing a membrane that can endure heat, retain its shape under pressure, and maintain stability along a laser beam's axis.
The team constructed a miniature lightsail tethered within a larger membrane to study the propulsive forces in a controlled environment. Utilizing advanced techniques, they patterned a silicon nitride membrane just 50 nanometers thick, resembling a microscopic trampoline. By applying argon laser light, they measured the radiation pressure experienced by the mini lightsail, observing its movements.
Co-lead author Lior Michaeli notes the complexities introduced by tethering the sail, which behaves as a mechanical resonator. The researchers turned the challenge of heat-induced vibrations into an advantage, enabling them to develop a method for measuring the light's force accurately.
A common-path interferometer was integrated into their experimental setup, allowing for precise detection of the sail's motion. This innovation ensures that environmental noise does not interfere with the measurements, leading to the ability to measure movements as small as picometers.
Future research aims to leverage nanoscience and metamaterials to control the motion and rotation of lightsails in space, with aspirations to create sails that can autonomously return to their intended path when displaced.
This research, detailed in the paper “Direct radiation pressure measurements for lightsail membranes,” published in Nature Photonics, represents a significant advancement in the quest for interstellar travel.