Electro-optical switch transmits data at record-low temperatures

March 16, 2017
An illustration of a silicon photonic micro-disk modulator operating at cryogenic temperatures. Light traveling down the silicon waveguide couples to the resonance of the micro-disk cavity. An electrical signal applied to the disk shifts the resonance and as a result modulates the light passing through the waveguide. (Rendered by Hanqing Kuang) Credit: Michael Gehl, Sandia National Laboratories

A silicon optical switch newly developed at Sandia National Laboratories is the first to transmit up to 10 gigabits per second of data at temperatures just a few degrees above absolute zero. The device could enable data transmission for next-generation superconducting computers that store and process data at cryogenic temperatures. Although these supercomputers are still experimental, they could potentially offer computing speeds ten times faster than today's computers while significantly decreasing power usage.

The fact that the switch operates at a range of temperatures, offers fast transmission and requires little power could also make it useful for transmitting data from instruments used in space, where power is limited and temperatures vary widely.

"Making electrical connections to systems operating at very cold temperatures is very challenging, but optics can offer a solution," said lead researcher Michael Gehl, Sandia National Laboratories, New Mexico. "Our tiny switch allows data to be transmitted out of the using light traveling through an optical fiber, rather than electricity."

In The Optical Society's journal for high impact research, Optica, Gehl and his colleagues describe their new silicon micro-disk modulator and show that it can transmit data in environments as cold as 4.8 Kelvin. The device was fabricated with standard techniques used to make CMOS computer chips, which means it can be easily integrated onto chips containing electronic components.

"This is one of the first examples of an active silicon optical device operating at such a low temperature," said Gehl. "Our device could potentially revolutionize technologies that are limited by how fast you can send information in and out of a cold environment electrically."

Optics excels at low temperatures

For low-temperature applications, optical methods provide several benefits over electrical . Because electrical wires conduct heat, they often introduce heat into a system that needs to stay cold. Optical fibers, on the other hand, transmit almost no heat. Also, a single optical fiber can transmit more data at faster rates than an electrical wire, meaning that one fiber can do the job of many electrical connections.

The micro-disk modulator requires very little power to operate—around 1000 times less power than today's commercially available electro-optical switches—which also helps reduce the heat the device contributes to the cold environment.

To make the new device, the researchers fabricated a small silicon waveguide (used to transmit light waves) next to a silicon micro-disk only 3.5 microns in diameter. Light coming through the waveguide moves into the micro-disk and travels around the disk rather than passing straight through the waveguide. Adding impurities to the silicon micro-disk creates an electrical junction to which a voltage can be applied. The voltage changes the material's properties in a way that stops the light from moving into the disk and allows it to instead pass through the waveguide. This means that the light signal turns off and on as the voltage switches on and off, providing a way to turn the ones and zeroes that make up electrical data into an .

Although other research groups have designed similar devices, Gehl and his colleagues are the first to optimize the amount of impurities used and the exact placement of those impurities to allow the micro-disk modulator to operate at . Their approach could be used to make other electro-optical devices that work at low temperatures.

Low error rate

To test the micro-disk modulator, the researchers placed it inside a cryostat—a small vacuum chamber that can cool what's inside to very low temperatures. The micro-disk modulator converted an electrical signal sent into the cryostat to an optical signal. The researchers then examined the optical signal coming out of the cryostat to measure how well it matched the incoming electrical data.

The researchers operated their device at room temperature, 100 Kelvin and 4.8 Kelvin with various data rates up to 10 gigabits per second. Although they observed a slight increase in errors at the highest data rate and lowest temperature, the error rate was still low enough for the device to be useful for transmitting data.

This work builds on years of effort to develop silicon photonic devices for optical communication and high performance computing applications, led by the Applied Photonics Microsystems group at Sandia. As a next step, the researchers want to demonstrate that their device works with data generated inside the low temperature environment, rather than only electrical signals coming from outside the cryostat. They are also continuing to optimize the performance of the .

Explore further: Researchers create practical and versatile microscopic optomechanical device

More information: Michael Gehl et al, Operation of high-speed silicon photonic micro-disk modulators at cryogenic temperatures, Optica (2017). DOI: 10.1364/optica.4.000374

Related Stories

More efficient nano-LED opens door to faster microchips

February 2, 2017

The electronic data connections within and between microchips are increasingly becoming a bottleneck in the exponential growth of data traffic worldwide. Optical connections are the obvious successors but optical data transmission ...

Making the switch to polarization diversity

January 31, 2017

Vast amounts of data transmit across the Internet and telecommunications networks delivering, for example, real-time video calls from one cell phone to another - across the world. As people send and receive increasing amounts ...

Photonics: Enabling next-generation wireless networks

March 12, 2014

Wireless transmission at microwave frequencies is important for high-data-rate transmission applications, such as mobile phone networks, satellite links and remote imaging. Now, Xianshu Luo and colleagues from the A*STAR ...

Time Lens Speeds Up Optical Data Transmission

September 28, 2009

(PhysOrg.com) -- Researchers at Cornell University have developed a device called a "time lens" which is a silicon device for speeding up optical data. The basic components of this device are an optical-fiber coil, laser, ...

Recommended for you

Two teams independently test Tomonaga–Luttinger theory

October 20, 2017

(Phys.org)—Two teams of researchers working independently of one another have found ways to test aspects of the Tomonaga–Luttinger theory that describes interacting quantum particles in 1-D ensembles in a Tomonaga–Luttinger ...

Using optical chaos to control the momentum of light

October 19, 2017

Integrated photonic circuits, which rely on light rather than electrons to move information, promise to revolutionize communications, sensing and data processing. But controlling and moving light poses serious challenges. ...

Black butterfly wings offer a model for better solar cells

October 19, 2017

(Phys.org)—A team of researchers with California Institute of Technology and the Karlsruh Institute of Technology has improved the efficiency of thin film solar cells by mimicking the architecture of rose butterfly wings. ...

Terahertz spectroscopy goes nano

October 19, 2017

Brown University researchers have demonstrated a way to bring a powerful form of spectroscopy—a technique used to study a wide variety of materials—into the nano-world.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.