A fundamental road block for all-optical information processing is the difficulty in realizing a silicon optical transistor with the ability to provide optical gain, input output isolation and buffer action. In this work, we demonstrate an all-optical transistor using optical nonlinearity in microrings. By using weak light to control strong light, we observed an On/Off ratio up to 20 dB. It can compensate losses in other optical devices and provide fan-out capability. The device is ultra compact and is compatible with currentcomplementary metal-oxide-semiconductor (CMOS) processing.
Varghese and co say the ratio of the gate signal to the supply is almost 6 dB. That’s enough to power at least two other transistors, which is exactly the fan out property that optical transistors require.
These guys have even built a device out of silicon with a bandwidth capable of data rates of up to 10 GHz.
That’s an impressive result, particularly the silicon compatibility.
Nevertheless, there are significant hurdles ahead before an all-optical computer made with these devices can hope to compete against its electronic cousins.
The biggest problem is power consumption. Much of the power consumption in electronic transistors comes from the need to charge the lines connecting them to the operating voltage.
In theory, optical transistors could be even more efficient–their lines don’t need charging at all. But in practice, lasers burn energy as if it were twenty dollar bills. For that reason, it’s not at all clear that optical transistors can match the efficiency of electronic chips.
And with the computer industry now responsible for almost 2 per cent of global carbon dioxide emissions, almost as much as aviation, power consumption may turn out to be the overarching factor for the future direction of information processing.