Integrated optical isolators for broadband multi-laser operation

Abstract Photonic integrated circuits commonly feature visible or near-infrared lasers that are vulnerable to destabilizing back-reflections and must be protected by isolators—non-reciprocal optical components enforcing one-way light propagation. Despite recent progress, high-performance isolators remain bulky off-chip components, while on-chip implementations suffer from challenging fabrication, high optical absorption or narrow optical bandwidth. Here we propose and experimentally demonstrate a magnet-free, intrinsically broadband travelling-wave isolator built from foundry-compatible components. Using radio-frequency electro-optic modulation to create synthetic motion across four parallel waveguides, we realize dynamic rotating destructive interference that continuously cancels backward-propagating light while leaving forward-propagating light unaffected. We reach ~30 dB peak isolation, maintain >24 dB isolation across a 30-nm-wavelength span with thermo-optic adjustment and show >20 dB isolation for two lasers simultaneously within 10 nm without any adjustment. The demonstration’s 770–800-nm-wavelength span covers key alkali atomic transitions, enabling on-chip laser isolation for atomic spectroscopy, laser cooling and locking applications. Our isolator approach, applicable from the visible to telecom wavelength spectrum, offers a compelling practical solution, opening the way for fully integrated atomic clocks, quantum sensors, advanced telecommunications and tunable laser systems on a single chip.