Scientists at Caltech have successfully adapted fiber-optic technology to silicon wafers by creating waveguides made from germano-silicate, the same material used in traditional optical fiber. The research team, led by Kerry Vahala with postdoctoral scholar Hao-Jing Chen and graduate student Kellan Colburn, published their findings in Nature. This advancement enables the fabrication of photonic integrated circuits (PICs) with ultralow loss characteristics suitable for computer chip manufacturing using standard 8- and 12-inch wafers.
The researchers arrange the optical pathways in spiral patterns, allowing light to travel extended distances within a compact chip footprint. This design mimics winding optical fiber around a spool but uses nanofabrication techniques to reduce the physical size. The germano-silicate approach offers significant advantages over existing silicon nitride platforms, particularly in the visible wavelength range. At visible wavelengths, the new platform outperforms silicon nitride’s previous performance record by a factor of 20, with researchers indicating room for further improvement.
The key to achieving such low loss at visible wavelengths lies in the material’s properties. Because germano-silicate has a comparatively low melting temperature, researchers can heat-treat the waveguides to achieve atomic-level surface smoothness, which substantially reduces scattering losses that typically limit visible-range photonic devices. Lasers produced using this platform demonstrate more than 100-fold improvements in coherence length compared to previous designs.
Applications for this technology span multiple fields. Ring resonators, which allow light to circulate repeatedly to enhance performance at specific frequencies, benefit dramatically from ultralow-loss waveguides even though the physical devices measure only millimeters. The circulating light effectively travels much longer distances, and minimal energy loss per cycle significantly extends device performance. Potential uses include optical clocks, atomic sensors, ion-trap quantum computing systems, and data center communications infrastructure.
Vahala characterized the platform’s utility as having a “Swiss Army-knife quality” due to its applicability across diverse technological domains. The research team describes their current results as representing significant progress rather than a final achievement, with expectations for continued advancement in this field.
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