Scientists at the California Institute of Technology (Caltech) have made significant progress in developing lightsails, a technology that could one day enable tiny spacecraft to journey to distant star systems. The breakthrough involves a new method to measure the force of laser light on ultrathin membranes, crucial for the success of the Breakthrough Starshot Initiative.
Launched in 2016 by the late Stephen Hawking and tech investor Yuri Milner, Breakthrough Starshot aims to send miniature probes to Alpha Centauri, the nearest star system to Earth. The plan relies on powerful lasers on Earth propelling delicate sail-driven probes through space, achieving unprecedented speeds without chemical propellants.
Caltech's Harry Atwater, the Otis Booth Leadership Chair of the Division of Engineering and Applied Science, explains that the lightsail will travel faster than any previous spacecraft, potentially opening interstellar distances to direct spacecraft exploration. His team developed a test platform to measure the force of lasers on a microscopic silicon nitride membrane, just 50 nanometers thick. This miniature sail, a 40-micron square sheet, vibrates when struck by a laser, allowing researchers to calculate the laser beam's force and power by detecting these tiny movements.
The study's lead authors, postdoctoral scholar Lior Michaeli and graduate student Ramon Gao, built a specialized setup called a common-path interferometer. This setup enables precise measurement of the membrane's motion by canceling out background noise, allowing for accurate force calculations. The platform can also measure side-to-side motion and rotations, paving the way for future lightsail designs capable of self-correction.
The team aims to integrate advanced nanomaterials and metamaterials to stabilize lightsails during their journey. This research represents a significant step towards observing optical forces and torques designed to allow a freely accelerating lightsail to ride the laser beam, paving the way for interstellar exploration.