Programming Optical Circuits for Specific Applications and Reducing Production Costs

June 06, 2020 by Luke James

Researchers have developed a new way to build power efficient and programmable integrated switching units on a silicon photonics chip.

Silicon photonics is an evolving technology which transfers data among computer chips by using optical rays which can carry far more data in less time than electrical conductors. The concept involves combining laser and silicon technology on a single chip, a silicon photonic chip. 

It is a hugely promising developing area of technology that saw impressive growth last year, with more than 3.5 million silicon photonic transceivers for data centers having being shipped, yielding revenues of around $364 million. From now until 2026, Global Market Insights expects the silicon photonics market to grow at over 30% year-on-year to a value of over $3 billion. 


Expanding Silicon Photonic Applications

Now, in a move that could see the silicon photonics market grow even more, researchers have developed a new method of building power-efficient and programmable integrated switching units on a silicon photonics chip. By enabling a generic optical circuit to be fabricated in bulk and then later programmed for specific applications, such as LiDAR, the new method could significantly reduce production costs—a major barrier for manufacturers—and enable wider access. 

"Silicon photonics is capable of integrating optical devices and advanced microelectronic circuits all on a single chip," said research team member Xia Chen from the University of Southampton. "We expect configurable silicon photonics circuits to greatly expand the scope of applications for silicon photonics while also reducing costs, making this technology more useful for consumer applications."


Xia Chen, University of Southampton

The wafer-scale prober being tested by the University of Southampton (left). The prober autonomously and accurately performs optical and electrical device testing at an average speed of less than 30 seconds per device. Image credited to Xia Chen, University of Southampton


Erasable Components

The team’s work builds on earlier research where an erasable version of an optical component was developed. This component, known as a grating coupler, was created by implanting germanium ions into silicon. These ions induce damage that alters the silicon’s refractive index in the area where they’re implanted. Once altered, heat can be applied to the local area using a laser annealing process which reverses the refractive index and erases the grating coupler. 

In their own research, the team describes how they applied this germanium ion implantation technique to create erasable waveguides and directional couplers, components that can be used to make reconfigurable circuits and switches. This is the first time that sub-micron erasable waveguides have been created in silicon. “…we found that a carefully designed structure and using the right ion implantation recipe can create a waveguide that carries optical signals with reasonable optical loss,” said Chen. 


A Wide Range of Applications

This approach was demonstrated by the researchers by designing and fabricating waveguides, directional couplers, and 1 X 4 and 2 X 2 switching circuits. Photonic devise from different chips tested before and after laser annealing showed consistent performance. And because the technique involves changing the routing of the photonic waveguide via a one-time operation, no additional power is used to retain the configuration when programmed. 

The technology developed by the research team could have a wide range of applications. These include integrated sensing devices for biochemical substances and optical transceivers for connections used in high-performance computing.