Optical waveguide connects semiconductor chips

September 24, 2012
Photonic Wire Bond Transmits Data in the Terabit Range

The wire bond is adapted to the position and orientation of the chips (credit: N. Lindenmann and G. Balthasar)

A team of Karlsruhe Institute of Technology (KIT) researchers directed by Professor Christian Koos has succeeded in developing a novel optical connection between semiconductor chips.

“Photonic wire bonding” reaches data transmission rates in the range of several terabits per second and is suited perfectly for production on the industrial scale.

In the future, this technology may be used in high-performance emitter-receiver systems for optical data transmission and, thus, contribute to reducing energy consumption of the Internet. The scientists published their results in the open access journal “Optics Express“.

Communication processes can be made quicker and more energy-efficient with photonic components. Development of high-performance optical emitters and receivers integrated on microchips has already reached a high level. However, there have not yet been any satisfactory possibilities of bridging semiconductor chips optically.

“The biggest difficulty consists in aligning the chips precisely such that the waveguides meet,“ explains Christian Koos, professor at the KIT Institutes of Photonics and Quantum Electronics (IPQ) and of Microstructure Technology (IMT) as well as member of the Center for Functional Nanostructures (CFN).

The team under Christian Koos tackled this problem from the other side: The researchers first fix the chips and then structure a polymer-based optical waveguide in a perfectly fitting manner. To adapt the interconnection to the position and orientation of the chip, the scientists developed a method for three-dimensional structuring of an optical waveguide.

They used two-photon polymerization to achieve high resolution. A femtosecond laser writes the freeform waveguide structure directly onto a polymer on the surface of the chip.

Prototypes of the photonic wire bonds had very small losses and a very high transmission bandwidth, in the range of infrared telecommunication wavelengths around 1.55 microns. They have demonstrated data transmission rates in excess of 5 terabits per second.

Potential applications of photonic wire bonds are complex emitter-receiver systems for optical telecommunication and sensor and measurement technology.

As the highly precise orientation of the chips in manufacturing is no longer required, the process is particularly suited for mass production. KIT researchers now plan to transfer this technology to industrial application in cooperation with partner companies.