Optical fiber underpins modern communication because its glass is extremely pure and its surface is ultra-smooth, so light propagates with ultralow loss. A Caltech team has now brought this fiber-like performance directly onto silicon wafers, opening the door to far more efficient integrated photonics.
Fiber glass directly on chip
In Kerry Vahala’s lab, researchers developed a way to fabricate on-chip waveguides from germano-silicate glass – the same glass used in telecom fiber. Instead of pulling glass into long fibers on a spool, they lithographically pattern it onto standard 8- and 12-inch semiconductor wafers.
The waveguides are laid out as tight spirals rather than straight lines. This gives light a very long optical path length while occupying only a tiny chip area, analogous to winding fiber on a spool but shrunk to the nanoscale.
Because the material is glass, these germano-silicate waveguides exhibit extremely low propagation loss and can be efficiently coupled to both optical fibers and semiconductor lasers – a key requirement for reducing the energy cost of large-scale server and data-center infrastructure.
Beating silicon nitride, especially in the visible
At near-infrared wavelengths, devices made on the new Caltech platform already match the performance of state-of-the-art silicon nitride photonic circuits, which are widely used today for low-loss on-chip optics.
In the visible spectrum, the advantage becomes dramatic: the germano-silicate platform surpasses silicon nitride by roughly a 20× reduction in loss. Combining such low loss with wafer-scale fabrication could enable new generations of silicon photonics, from energy-efficient data links to advanced optical and quantum information processing systems.
Source: ScienceDaily
