Photonic integrated circuits are essential to many technologies, including fiber-optic communications, mapping systems, and biosensors.
These circuits—which use photons instead of electrons—employ optical isolators that allow photons to travel in only one direction, which prevents light from re-entering the system and destabilizing it. But guiding light in one direction often requires large magnets, making these circuits challenging to create on a small scale.
Researchers at the University of Chicago’s Pritzker School of Molecular Engineering (PME) have developed a new way to guide light in one direction on a tiny scale. By coupling light confined in a nanophotonic waveguide with an atomically thin, two-dimensional semiconductor, the researchers exploited the properties of both the light and the material to guide photons in one direction.
The result—a small, tunable on-chip photonic interface—could lead to smaller photonic integrated circuits that could be more easily integrated into modern technologies, including computing systems and self-driving cars.
“We see this research as paving the way towards a whole new class of integrated photonic circuits,” said Asst. Prof. Alex High, who led the research with graduate students Amy Butcher and Robert Shreiner, and postdoctoral fellow Kai Hao. The results were published in Nature Photonics.
Coupling light with a 2D material
In electronic circuits, electrons move through wires to transfer energy. Photonic integrated circuits work similarly, but instead of electrons in wires, light is channeled along waveguides.
To create a new element for photonic circuits, High and his team interfaced a two-dimensional material—tungsten diselenide—with a photonic waveguide. The unique properties of the material’s band structure enable it to interact with light differently based on the helicity of the light’s polarization. In nanophotonic structures, where light is confined below its wavelength, circular polarization arises naturally, and the helicity is locked to the light’s propagation direction.