Artificial gauge fields enable arbitrary-ratio optical splitting on chip

Researchers at ShanghaiTech University have developed a waveguide coupling method that uses artificial gauge fields to cut crosstalk, flatten wavelength dispersion and control power splitting on integrated photonic chips. The work could improve dense optical interconnects, beam steering and other broadband on-chip photonic systems.

Why it matters: - Integrated photonic chips need tight waveguide spacing for more functions in less space, but closer spacing usually increases crosstalk. - Conventional evanescent coupling also varies with wavelength, which limits bandwidth in dense chips and beam-steering devices. - The new method targets both problems at once, which could help enable smaller, higher-performance photonic chips for communications, sensing and optical computing.

What happened: - Prof. Yi Zou's group at ShanghaiTech University proposed an on-chip coupling control method based on artificial gauge fields. - The results were published in Opto-Electronic Advances under the title “Dispersionless coupling control enabled by artificial gauge fields for dense waveguide arrays and arbitrary-ratio power splitters.” - The team designed and fabricated ultra-dense silicon-on-insulator waveguide arrays with a center-to-center pitch of 750 nm.

The details: - The 750 nm pitch is about half the optical wavelength in the telecom band and much smaller than the spacing typically used to limit crosstalk. - Experiments showed crosstalk below –20 dB across a 100 nm band from 1500–1600 nm. - The arrays added almost no extra propagation loss. - The design offers a path to high-density on-chip optical interconnects, compact delay lines and wide-field-of-view optical phased arrays. - The researchers also used artificial gauge fields to engineer on-chip coupling, not just suppress it. - By tuning waveguide trajectory modulation amplitude and coupling length, the team built near-dispersionless directional couplers. - The couplers held stable power-splitting ratios over a broad wavelength range. - Splitters with arbitrary ratios including 60:40 and 70:30 were demonstrated. - The wavelength independence of those splitters was verified over 1500–1600 nm. - The results show artificial gauge fields can both suppress unwanted coupling and compensate for coupler dispersion. - The team then applied the approach in a two-dimensional optical phased array. - A 32-channel array produced a broadband Gaussian-weighted intensity distribution that reduced far-field sidelobes. - The phased array achieved a 120° × 14.5° field of view and sidelobes below –17 dB near the main beam direction. - The paper says this confirms the potential of artificial-gauge-field coupling control for wide-field-of-view, low-sidelobe beam steering.

Between the lines: - The work shifts artificial gauge fields from a physics concept into a practical chip-design tool. - The key advance is not only lower crosstalk, but also active control over coupling behavior across wavelength. - That combination matters for systems that need dense integration and consistent optical performance at the same time.

What's next: - The approach could be used to design denser optical interconnects, broadband splitters and phased arrays with less crosstalk. - The underlying method may support future chip architectures that require both compact layouts and precise power distribution. - The ShanghaiTech group says its broader research focuses on high-performance, low-power and highly integrated optoelectronic information systems.

The bottom line: - Artificial gauge fields now look like a practical route to make integrated photonic chips denser, broader-band and more controllable at the same time. - More information