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DAtacommunications based on NanophotoniC Resonators

Mid-Term Report Summary - DANCER (DAtacommunications based on NanophotoniC Resonators)

The large scale movement and storage of data has now become an essential component of society. The emergence of Google, Facebook, Amazon and so many others have changed the face of society and are now indispensable parts of everyday life. A key challenge for the 21st century is, therefore to provide billions of people with the means to access, move and manipulate, what has become, huge volumes of information. This is key to maintaining the expected levels of access and providing further advances. A significant fraction of the world’s economy is now based on the internet and is a significant area for future growth. The Internet experience is now, somewhat invisibly, built around data centers, huge warehouses of computers connected together, with the efficient operation of these crucial but huge amounts of energy are consumed in this process.
The problems stems from the inefficient movement of data around and between computer chips. As clock speeds have increased and transistors have shrunk, the metal wires connecting them have become less and less efficient and 50-80% of a computer processor’s power consumption now occurs in these interconnects. Optical links are the solution to this problem. As optical waveguides do not suffer from resistive loss and do not require the line to be charged to the operating voltage, huge data transmission rates are possible. However, the current state of the art is still orders of magnitude away from the efficiencies (in terms of cost, power and volume) required.
The DANCER project is developing a new framework for optical interconnects and will provide a common platform that spans Fibre-to-the-home to chip-to-chip links, even as far as global on-chip interconnects. The project is based on the efficient coupling of the Photonic Crystal resonators with the outside world. These provide the ultimate confinement of light in both space and time allowing orders of magnitude improvements in performance relative to the state of the art, yet in a simpler simple system. This technique has been used to demonstrate a new type of power efficient hybrid laser that combines the best attributes of indium phosphide based amplifiers and silicon nanophotonics. Very good spectral purity was realised, with excellent side mode suppression ratios of up 55dB realised, which is comparable with Distributed Feedback Lasers that require more complex and costly fabrication. This laser show low threshold currents will provide a platform for lower power optical interconnects. A preliminary demonstration of frequency modulation has been made and will elaborated to enable new types of modulation to be realised. A patent has been filed to protect this design. A process is being developed to produce vertically coupled photonic crystals with integrated pn junctions in a CMOS line. Ultimately, this facility will be compatible with small-to-medium scale production.
High Q photonic crystal cavities have been demonstrated in polycrystalline silicon depositing using Low Pressure Chemical Vapour Deposition. This process will provide a platform for nanophotonics that has increased compatibility with the fabrication of electronic components providing a route to photonics-electronics integration, which will a major focus of the second half of the project. A wafer scale testing procedure have been demonstrated that can be used to screen devices- an important and often forgotten aspect.