Can All-Optical Chips Achieve Light Speed Computation?
By Emily Newton
Optical computing could be the next big thing in semiconductor production. Light has already become a go-to choice for transmitting data, but most systems still must translate photons into electrical signals to process information. All-optical chips could change that.
All-optical signal processing (AOSP) has been something of a holy grail for the electronics industry. The benefits of computing at the speed of light are obvious, but making that dream a reality has proved challenging. Some recent innovations in optical computing may offer a way forward.
Recent Advances In All-Optical Chips
Many older photonic processing systems rely on optical-electrical-optical (OEO) conversions. While it’s faster than all-electric computation, the repeated translation introduces bottlenecks and the potential for signal loss. Silicon-based AOSP is a more promising alternative, but often leads to lots of crosstalk and limited nonlinear interactions.
One recent study found a way around these barriers by combining multiple photonic chips serving different purposes and employing silicon waveguides and resonators to limit interference. The system achieved logic operations at an eye-watering 100 gigabits per second with losses as low as 0.17 decibels per centimeter.
As the nanomanufacturing processes the study used become more common, this could make AOSP chips practical enough for real-world applications. Electronics could process signals as fast as they receive them without worrying about losses and transmission errors.
Programmability also has been an issue, as nonlinear optics can usually only serve a single, purpose-built function. However, researchers at Cornell University have recently found ways around this barrier, too. The team created multiple light profiles across various wavelengths by beaming different photonic patterns onto a reactive material instead of relying on a pre-manufactured physical pattern.
Being able to change these patterns in real time makes programmable photonic chips a reality. Optical systems could even change their functions after implementation, making them versatile on top of being fast. That versatility could be key to AOSP devices replacing older, electrical-only or OEO alternatives.
Remaining Barriers To All-Optical Chips
While these studies show that programmable photonic chips are slowly becoming a viable reality, there are still obstacles in the way. Recent AOSP systems may overcome the versatility and signal integrity problems of the past, but scalable manufacturability remains a concern.
Designing these components requires hyper-precise, nano-scale production methods. Semiconductor fabs may not have the resources necessary to deploy such advanced techniques at scale. Nanomanufacturing aside, optical equipment fabrication already requires cleanrooms capable of 400 to 750 air changes hourly, requiring additional specialized equipment.
Manufacturing consistency presents a similar challenge. At such a small scale, any variation between components could dramatically alter an all-optical chip’s performance. Material quality is also more impactful, as slight differences could lead to differently behaving light patterns. Meeting these demands may push the need for supply chain assurance and automation even higher, and achieving these goals has already proven challenging.
Even when the industry overcomes these practical barriers, light-speed computation is still uncertain as a possibility. Fiber optics can only reach roughly 75% the speed of light, which is remarkably fast but a ways away from actual light speed. That only reflects data transmission, too. Processing that information — even optically — would introduce a slight bottleneck.
The Future Of Computing At The Speed Of Light
There may be some helpful changes on the horizon. One study developed a method for printing and transferring photonic components to make all-optical chip manufacturing more efficient and less error-prone. Researchers managed to transfer 119 photonic crystal cavities in just one session, all while monitoring their performance. At scale, this process could mean faster, more consistent AOSP component production.
Novel materials could also offer relief for programmable photonic chip manufacturing. Newer photonic glasses promise high refractive indices and ultra-low losses, giving fabs more breathing room when assembling sensitive optical components. Some materials even allow manufacturers to adjust their properties, making it possible to meet multiple needs with the same resources. That flexibility could lower supply chain costs and complexity.
Further research into nanomaterials and nano-scale fabrication will likely lead to similar advances in AOSP production. As researchers experiment with new processes and materials, it may become possible to reach closer to the speed of light in actual computing, not just data transmission.
Many of today’s cost concerns will fall over time, too. As more facilities embrace modernization, more will become able to achieve the precision and cleanliness necessary for all-optical chips. The technology will become increasingly affordable as its processes and materials become more common by the simple rule of scale. When that happens, it could lead to even faster advances in light-speed computation.
An All-Optical Future Is Fast Approaching
Programmable photonic chips have moved from goal to reality in relatively minimal time. Large-scale all-optical computing may seem like something out of the future for now, but the industry’s current trajectory could make it happen before long.
AOSP chips will provide unparalleled power, energy efficiency, and data privacy. The technology is too promising not to pursue, and researchers have already made massive strides toward unlocking its potential. The all-optical future will arrive, possibly within the coming years.