When you think of light traveling down some kind of narrow channel, which I know you do all the time,
you probably think of high-speed internet connections, telephone lines, or even those
pre-lit Christmas trees. But did you know that optical connections are actually taking the
place of traditional metal traces in actual computer chips? This field is called silicon
photonics, and it's not some kind of gimmicky speculative technology. Products that use silicon
photonics are already being deployed in data centers by the millions to help keep up with
how much pressure we're increasingly putting on cloud systems these days, especially considering
how rapidly AI is expanding. The basic idea is to use photons instead of electrons to move data
around. The best part is that chip makers are manufacturing the means to do so directly onto
silicon wafers, meaning that you don't need costly exotic materials in order to pull this off.
Silicon photonics uses waveguides that the light can move through, as well as freaking laser beams,
as a light source. These hybrid silicon lasers are made from both silicon and other semiconductors,
such as indium and gallium compounds, so they can be built directly onto the chip,
obviating the need for extra laser equipment outside the chip, which can be costly.
This technology has already been in use for a few years in transceivers that convert electrical
signals to and from optical ones. You plug them into a server and use fiber optic cable to connect
to another server elsewhere in a data center, up to several kilometers away. A piece of tech
that's also proven useful for supporting current 5G networks. But there's been a more recent
development that might make those external transceivers obsolete. Instead of relying on a
separate transceiver to handle the actual photonics part of the chain, recent work has looked more at
integrating silicon photonics directly onto a chip package. In 2022, Intel showed off a laser
setup that used tiny micro rings to save enough space to fit the actual photonics next to the die,
with each ring producing different light wavelengths, allowing more data to be transferred
than if you just used a single wavelength. Intel also revealed a chip they had been working on for
DARPA in 2023 that used optical chiplets. These chiplets sit on the same package as the actual
compute die and are responsible for doing the conversions between electrical and optical.
So you'd be connecting fiber optics directly to these chiplets,
again eliminating the need for external transceivers when this tech hits the marketplace.
But beyond the cost advantages of moving photonics as close to the compute die as possible,
we might need silicon photonics more and more as the years go by. As our bandwidth needs just
continue to grow, there's a good chance we'll start hitting the limits of what's possible
with standard metal traces in terms of power or data integrity. The thinking is that it could be
cheaper to use silicon photonics instead of trying to find ways to shove more and more
data down a metal trace, and that photonics could offer a superior error rate to traditional
electronics. But silicon photonics isn't just about ensuring the cloud can continue to deliver
fine YouTube videos like this one to your screen. Because the general idea is put optical technology
into silicon, it has other applications such as LiDAR for self-driving cars, healthcare
diagnostics that involve shooting light into tissues, and even better sensors for AR and VR
headsets. It's unclear if silicon photonics will have a big role to play in home PCs at some point,
but if you really want optical tech in your personal rig in the meantime,
you could always just put in a Blu-ray drive. They're not dead yet.
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