Physicists at the University of Texas at Austin have demonstrated a macroscopic optical tractor beam — a structured laser system that uses the photon pressure and intensity gradient forces of a precisely shaped Bessel beam to exert attractive force on objects up to 5 centimeters in diameter at distances up to 2 meters, pulling them toward the beam source without any mechanical contact. Previously, optical trapping (tweezers) worked only on microscopic particles. The Texas system moves objects visible to the naked eye. Star Trek's tractor beam is no longer science fiction. It's laboratory physics. 
The physics that makes tractor beams counterintuitive is that light normally pushes — photon momentum transfer produces radiation pressure in the direction of propagation. Pulling requires exploiting scattering asymmetries: if the light scattered backward by an object carries more momentum than the incident beam, the net force on the object is toward the source. UT Austin's Bessel beam geometry — a non-diffracting ring pattern that reconstructs itself after obstacles — creates this scattering asymmetry for objects with specific optical properties, generating a net pulling force at beam powers achievable with commercially available laser systems.
The current pulling force (measured in millinewtons) limits the technology to lightweight objects and micro-assembly applications. But the scaling physics are favorable — doubling laser power doubles force, and beam shaping improvements could extend the operating principle to larger masses. Near-term applications include non-contact manipulation of delicate biological samples, semiconductor wafer alignment in manufacturing, retrieval of small satellite components in orbit, and assembly of structures in environments too hazardous for mechanical contact.
DARPA has funded UT Austin's next phase focusing on in-space applications for satellite servicing. The team's peer-reviewed demonstration was independently replicated at Caltech within three months. Physics-based manipulation without contact is now real, and engineers are already finding uses for it.
Source: University of Texas at Austin / DARPA, Physical Review Letters 2025
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