The synergy of electronic processing and optical communications has powered the decades-long boom in information technology. But the need to convert signals back and forth between electrical and optical forms is becoming a bottleneck for the emerging field of integrated photonics. Steering lidar laser beams is one application for a switch that is partly photonic and partly plasmonic.
From an article in IEEE Spectrum by Jeff Hecht.
A new type of switch that combines electrical and mechanical effects to redirect light could open the door to large-scale reconfigurable photonic networks for several applications including beam steering for lidars and optical neural networks for computing.
Currently, integrated photonics are used in high-performance fiber-optic systems , and a joint government-industry program called AIM Photonics is pushing their manufacture. However, current optical switches are too big and require too much power to blend well into integrated photonics. The new hybrid nano-opto-electro-mechanical switch has a footprint of 10 square micrometers and runs on only one volt—making it compatible with the CMOS (complementary metal-oxide-semiconductor) silicon electronics used in integrated photonics, says Christian Haffner from the Swiss Federal Institute of Technology in Zurich now working at the National Institute for Standards and Technology (NIST) in Gaithersburg, Maryland and the researcher who led the team that developed it.
The root of the problem Haffner set out to solve is that photons and electrons behave very differently.
Photons are great for communications because they travel at the speed of light and interact weakly with each other and matter, but they are much larger than chip features and require high voltages to redirect them because of their weak interactions.
Electrons are much smaller and interact much more strongly than photons, making them better for switching and for processing signals. However, electrons move slower than light, and more energy is needed to move them.
Long-distance communication systems process signals electronically and convert the signal into light for transmission, but converting between signal formats is cumbersome for local transmission. The new switch makes it possible to redirect optical signals on the integrated photonic circuit without having to convert them to electrical format and then back to optical format for further transmission.
In Science, Haffner and colleagues describe a hybrid nano-opto-electro-mechanical switch that would occupy only about 10 square micrometers on an integrated photonic circuit. Their switch is a small multilayered disk sitting at a T-junction between two optical waveguides—stripes of transparent silica that guide light—that meet at a right angle. The top layer of the disk is a four-micrometer circle of 40-nanometer gold membrane resting on a small piece of alumina on layer of silicon deposited on silica. That structure acts as a curved waveguide resonant with both the input and output waveguides, so it can transfer resonant light between the two.
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