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Toward Practical Laser-Driven Light Sails Using Photonic Crystals

Researchers have created a photonic‑crystal light sail (PCLS) that uses a three‑dielectric nanostructure of germanium pillars, air holes, and polymer matrix to achieve high reflectivity at a propulsion‑specific wavelength. Simulations and electron‑beam fabricated prototypes demonstrate about 90 % reflectivity at 1.2 µm and the ability to generate continuous thrust from a 100‑kW laser on a 1 m² sail, reaching several hundred meters per second in an hour. The design offers narrow band‑gap reflectivity while remaining transparent to solar radiation, addressing the mass‑efficiency trade‑off of conventional metal‑coated sails. Although still far from interstellar speeds, the approach could enable lightweight probes for interplanetary missions.