Photonic laser thruster may shorten trip to Mars down to 1 week from 6 months

Still just proof of concept.

"For decades, rocket scientists have tried to overcome the inefficiency of photon thrusters by amplification based on optical cavities separated from laser sources, but failed," the institute said. "In contrast, Bae’s PLT (patent pending) places the laser medium within a resonant optical cavity between two platforms to produce a very stable and reliable thrust that is unaffected by mirror movement and vibration -- ideal for spacecraft control or propulsion."