Most high-speed networking is done using optical fibers. The hardware on each end of these fibers has to convert the optical signals to electronic ones in order to figure out a packet’s destination and will often return it to optical form before sending it on toward its destination.
Researchers at the Japanese telecom NTT find all that converting a bit wasteful and are working on ways to avoid it. They’ve recently published a paper that includes a description of a working 115-bit optical Random Access Memory device, made of a carefully structured series of photonic crystals, each of which can store light of a different wavelength.
Photonic crystals are made of layered semiconductors, with the precise structure (the thickness and spacing of the layers) determining how they interact with light—it’s possible to make photonic crystals that selectively block or transmit a narrow frequency range.