Caltech Develops Fiber-Optic Level Performance on Silicon Chips

Researchers at Caltech have developed a method to achieve ultralow signal loss on silicon chips, comparable to that of optical fibers. This breakthrough could pave the way for advanced photonic integrated circuits (PICs) with applications in optical clocks, gyroscopes, AI data centers, and quantum computing.

The team, led by Kerry Vahala, utilized germano-silicate glass, the same material used in optical fibers, to create waveguides on silicon wafers. These waveguides are arranged in spirals, allowing light to travel longer distances within a compact space, similar to winding optical fiber around a spool. This design significantly reduces energy loss, enhancing the efficiency of optical devices.

At visible wavelengths, the new platform outperforms traditional silicon nitride devices by a factor of 20. This is achieved by reflowing the waveguides' surfaces to atomic smoothness, minimizing scattering losses. The improvement in coherence for lasers using this platform exceeds previous designs by over 100 times, making it suitable for chip-scale atomic sensors and ion-trap systems.

The research highlights the importance of achieving low loss over long distances, even on small chips. Devices like ring resonators benefit from extended light circulation, which enhances performance. The ability to maintain low loss over effective distances of meters or kilometers is crucial for high-performance optical devices.

The findings, published in Nature, demonstrate the versatility of the new platform, which can be applied across various technologies. The study was conducted by postdoctoral scholar Hao-Jing Chen and graduate student Kellan Colburn in Vahala's lab, with contributions from Henry Blauvelt of Emcore.