Researchers create photonic transistors, a potential path for the continuation of Moore’s law

Researchers at the University of Vienna have successfully demonstrated a semiconductor transistor that relies on light, rather than electrical impulses, to flip between a “0″ and a “1.” It’s the second time to bat for the Vienna team, who originally demonstrated a similar design back in 2011, but this new architecture has a critical advantage that the initial model lacked. The first design required an external magnetic coil. The new method doesn’t, which drastically reduces power consumption and increases switching speed.
Here’s how the concept works. Light, once generated, has a particular polarization. That polarization can theoretically be shifted, but doing so without losing a significant amount of the total wave has always been difficult. By using terahertz radiation in conjunction with a particular type of polarization filter, the team was able to shift light back and forth using an electrical potential of less than one volt.

That’s significant, for several reasons. As team head Andrei Pimenov explains, “The components of today’s computers, in which information is passed only in the form of electrical currents, cannot be fundamentally improved. To replace these currents with light would open up a range of new opportunities.” Pimenov’s comments are in line with trends that we’ve discussed over the past two years. In a paper from 2011 on multi-core scaling, an extensive investigation of best-case scenarios for conventional CMOS scaling concluded that:

The path to 8nm in 2018 results in a best-case average 3.7x speedup; approximately 14% per year for highly parallel codes and optimal per-benchmark configurations. The returns will certainly be lower in practice… as the benefits of multicore scaling begin to ebb, a new driver of transistor utility must be found, or the economics of process scaling will break and Moore’s Law will end well before we hit final manufacturing limits.

Intel’s work on Near Threshold Voltage is designed to improve transistor efficiency by finding ways to operate processors at low power, but it doesn’t impact the fundamental limits at which we can switch silicon on or off. The need for non-standard approaches to the problem that can conceivably switch at lower voltages and equivalent speeds is critical, and the terahertz research that the Vienna team has pioneered could be part of a long-term replacement for traditional silicon.

As with all potential silicon replacements, the gap between building a a single photonic transistor and packing 4.3 billion of them into a processor and shipping it for $300 is significant, but the research team has made notable advances in just two years. If breakthroughs continue at this pace, we might see viable commercial structures before the end of the decade.