Understanding silicon photonics technology

Silicon photonics technology sounds like something from Star Trek. In reality, it involves lasers, semiconductors and just a bit of biology.

Those humble chips running the servers in your data center are evolving, as optical components move onto the chip itself. Known as silicon photonics technology, this method involves the use of silicon semiconductors as the medium for optical signals, allowing much faster digital signaling than is currently possible with traditional electron-based semiconductor devices.

Silicon photonics involves several core components. First, a laser is at the heart of any optical device. Current lasers use silicon and indium phosphide to produce coherent infrared laser light. Photons must then be modulated to break the light into optical pulses. Optical waveguides and other interconnections are necessary to move pulses from one place to another. And since a 100% optical system – i.e.  all optical chips with optical interconnections -- is probably still decades away, there must also be a means of converting electronic signals into optical signals and back again.

Fortunately, every one of these optical components can be fabricated using the same basic technologies currently used to manufacture electronic semiconductors. In fact, it is entirely possible to fabricate electronic and optical components on the same substrate, to create hybrid chips that can perform myriad telecom and network functions.

Over the near term, silicon photonics chips will be deployed in high-speed signal transmission systems, which far exceed the capabilities of copper cabling. Earlier this year, Kotura Inc. announced its Optical Engine, which is capable of achieving data rates of 100 Gbps through the use of wavelength division multiplexing, allowing multiple data signals at different wavelengths to share the same optical pathways. Such devices are suited for data centers and high-performance computing (HPC) applications where standard copper-based Ethernet networking is inadequate. Other major chip makers like IBM, Intel and NEC are also developing silicon photonics devices.

As silicon photonics evolves and chips become more sophisticated, expect to see the technology used more in processing tasks such as interconnecting multiple cores within processor chips to boost access to shared cache and busses. Eventually, silicon photonics may be involved in actual processing—augmenting and perhaps even replacing a chip's semiconductor transistors with optical equivalents for greater computing performance.

Another application of silicon photonics includes biometrics. Researchers at universities like the Center for Nano- and Biophotonics at Ghent University in Belgium are using the technology to create implantable medical devices like blood glucose meters using an on-chip spectrometer along with other medical diagnostic/detection devices.

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