An anisotropic metamaterial waveguide cladding keeps light travel on track throughout a computer chip, preventing leaked and jumbled bits of information. (Credit: Purdue University image/Saman Jahani)

Replacing traditional computer chip components with light-based counterparts will eventually make electronic devices faster due to the wide bandwidth of light. Because processing information with light can be more efficient than with electrons, there is good reason to use it. But light and the bits of information it carries tend to leak and scatter out of the tiny components that must fit on a chip.

A Purdue University-led effort has built a novel cladding along the highways for light travel, called waveguides, to prevent information leaks — particularly around sharp bends where light bounces off-track and scatters. Information then gets lost or jumbled rather than communicated throughout a device. Preventing this could facilitate the integration of photonic with electric circuitry, increasing communication speed and reducing power consumption.

What makes the waveguide cladding so unique is anisotropy, meaning that the cladding design enables light to travel at different velocities in different directions. By controlling the anisotropy of the cladding, the researchers prevented light from leaking off-track into other waveguides, which would create "crosstalk," or mixing, of information. Instead, bits of information carried by light bounce off by total internal reflection and stay strongly confined within the waveguide. Since the waveguide is an extreme skin-depth structure, any leakage that does happen will be really small. This approach can therefore pave the way for dense photonic integration on a computer chip.