A new type of switch that combines electrical and mechanical effects, an opto-electro-mechanical switch, to redirect light could pave the way for large-scale reconfigurable photonic networks for several key applications such as optical neural networks for computing and beam steering for lidars.
At present, integrated photonics are used in high-performance fibre-optic systems, however, current optical switches are too big and are very power inefficient. These characteristics do not lend well to the switches’ use in integrated photonics that requires power efficiency and a small profile.
With the current need to convert signals back and forth between both electrical and optimal forms becoming a hindrance for further development of integrated photonics which has powered the boom in information technology, something needed to be done.
Tiny, energy-efficient light switch. Image Credit: IEEE Spectrum.
The Opto-Electro-Mechanical Switch
This new hybrid switch, recently featured in Volume 366 Issue 6467 of Science Magazine and developed by Jürg Leuthold and his team from the Swiss Federal Institute of Technology, is a solution to the above problems with an ultra-small footprint of only 10 square micrometers and an operating voltage of a single volt, 1 V. This makes the switch compatible with the CMOS silicon electronics used in integrated photonics.
To achieve this super small profile and energy consumption, the Swiss researchers used ‘plasmonics’ technology. In this technology, light waves are tightly squeezed into structures that are much smaller than the wavelength of the light, something that should be impossible according to the laws of optics. It can be achieved, however, by guiding the light along a boundary between a metal and a dielectric such as air or glass.
Electromagnetic waves of the light partially penetrate the metal and cause the oscillation of electrons within it. This results in a hybrid made of a wave of light and an electronic ‘excitation’—the plasmon.
Although optical switches based on plasmons were precited over a decade ago, real-life commercial applications have failed thus far due to the large losses seen when transporting photons through plasmonic devices. This means that high switching voltages are required.
With this optical switch based on plasmons, it is possible to redirect optical signals on the integrated photonic circuit without having to convert them to an electrical format and back for further transmission.
Light passing through silicon structures called waveguides. Image Credit: IEEE Spectrum.
Applications from Quantum Computing to Cars
The opto-electro-mechanical switch and the technology used within could potentially allow for larger-scale, reconfigurable photonic networks for a huge range of different applications.
Some of these applications include LIDAR systems for electric vehicles where the intensity and direction of light beams must be varied quickly and accurately, this is something that can be achieved using fast and compact switches that are not delayed by the needless conversion between signal formats and back again.
The switches could also be used in optical neural networks that mimic the human brain where they would be used as elements that learn to recognize certain objects at lightspeed.
Speaking about the switch, Christian Haffner, project leader, said, “Because we only use the plasmons for the short trip around the switching membrane, we have substantially lower losses than those of current electro-optic switches”, Haffner explains. “Also, we made the gold membrane very small and thin, so that we can switch it very fast and with a small voltage.”
It has already been demonstrated that this switch can be flicked on and flicked off millions of times per second using little more than one volt. It is thought that this will eventually make the bulky and power inefficient amplifiers typically used in electro-optical systems a thing of the past.