The quest to transform the basis of computing from electrons to photons has been full of challenges. The aim has been to get photonic circuits to do what electronic ICs do but do it much faster—at the speed of light, achieving it has remained elusive.
Researchers at ITMO University in St. Petersburg, Russia suggest that a new technique could be a big step toward photonic ICs and optical computing. It uses a single silicon nanoparticle as an optical transistor.
In research published in the journal Nano Letters, the Russian scientists turned away from using nanoparticles to control the absorption of light and instead have aimed at gaining control of how light scatters off of the nanoparticle. In a press release Sergey Makarov, lead author of the study and senior researcher at the ITMO explained:
Generally, researchers in this field are focused on designing nanoscale all-optical transistors by means of controlling the absorption of nanoparticles, which, in essence, is entirely logical. In high absorption mode, the light signal is absorbed by the nanoparticle and cannot pass through, while out of this mode the light is allowed to propagate past the nanoparticle. However, this method did not yield any decisive results… Our idea is different in the sense that we control not the absorption properties of the nanoparticle, but rather its scattering diagram. Let’s say, the nanoparticle normally scatters almost all incident light in the backward direction, but once we irradiate it by a control pulse, it becomes reconfigured and starts scattering light forward.
The ITMO scientists were able to achieve this control over the scattering of light by irradiating a silicon nanoparticle with intense and ultrashort laser pulses. The laser pulse changed the particle’s properties, causing it to switch the direction in which the incident light was scattered.
The researchers measured the speed at which it took light to trigger the nanoparticle switch. To active the nanoparticle it took no more than tens of femtoseconds (10−15 seconds) and to deactivate it was around several picoseconds (10−12 seconds). This compares rather favorably to silicon electron-based switches at around 0.1 - 1 nanoseconds.
So far, the Russian scientists have only experimented with the control beam. In future research they plan to introduce a signal beam to complete the device.