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Ghent University 2009-12-17
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It's a small world...

Small world: Electron Micrograph
The small world as seen through a scanning electron microscope.

The Photonics Research Group of Ghent University-IMEC has fabricated a world map on a scale of 1 trillionth. Using CMOS fabrication tools, IMEC has reduced the 40-thousand-kilometer circumference at the equator down to 40 micrometer, about half the width of a human hair. The map is put in a corner of a optical silicon chip designed for one of the group's research projects on nanophotonic integrated circuits. The scale reduction enables more complex optical functions on a single chip for applications in telecommunication, high-speed computing, biotechnology and health-care. Noteworthy, the factor of 1 trillion corresponds to the scale prefix Tera (like in Terabyte), but in this situation it would be better to call it ‘Terra’-scale.

Scale of the world map
Scale of the world map. It is hidden in the bottom right corner of a photonic chip.

On the technical side

  • The world map was defined on a silicon photonics test chip in IMEC’s clean-room for 200mm processing, using the same high-resolution optical lithography techniques as used for microelectronics fabrication, and the fabrication consisted of a 30-step process including layer depositions and chemical etching steps on a silicon-on-insulator wafer. Four different layer thicknesses can be resolved, corresponding to four different images, or mask layers, that have to be patterned separately. The tiny world map was piggy-backed onto a test and development chip for new nanophotonic circuitry.

  • The silicon photonics technology that is being developed with these chips integrates optical circuits onto a small chip: Light can be manipulated on submicrometer scale in tiny strips of silicon called waveguides or photonic wires. Using the unique properties of silicon, combined with state-of-the-art manufacturing technology, these silicon photonic circuits can pack a million times more components on the same footprint as today’s commercial glass-based photonics.

  • The circuits developed on this particular chip were used to demonstrate photonic wires with the lowest propagation losses. Also, structures were developed to improve the efficiency of coupling light from the outside world (like an optical fiber) to the wires on chip.

  • To put it in perspective, the smallest features resolved on the map are about 100 nanometer (corresponding to 100km), which is still a several times larger than the today’s state-of-the-art transistors.

 Small world: Microscope image
The small world as seen through an optical microscope. The different colors are caused by interference effects in the different layer thicknesses of Silicon.

The Photonics Research Group is a 60-people strong laboratory of Ghent University (Ghent, Belgium) and is associated with the Interuniversity Microelectronics Center (IMEC), located in Leuven, Belgium. The group focuses on the research and development of smart photonic chips for future application in communications, identification, biosciences and health care, building on technologies developed for the microelectronics industry. The use of silicon and microelectronics fabrication can drastically reduce the size, power consumption and cost of photonic chips, bringing them closer to integration with consumer electronics, cell-phones as well as smart distributed sensor networks and point-of-care diagnostics.


Photonics group:
Ghent University:

Contact: Wim Bogaerts., +32-9-264 3324


World map design: Wim Bogaerts
Design support: Pieter Dumon, Jin Guo
Fabrication Process: Shankar Kumar Selvaraja, Peter Verheyen
Images: Dirk Taillaert, Liesbet Van Landschoot
and all the people at Ghent University and IMEC who contribute to the results of Photonics Research Group.

 Relevant publications

P. Dumon, W. Bogaerts, A. Tchelnokov, J.-M. Fedeli, R. Baets, Silicon Nanophotonics,Future Fab International (invited), 25, p.29-36 (2008)

P. Dumon, W. Bogaerts, R. Baets, J.-M. Fedeli, L. Fulbert, Towards foundry approach for silicon photonics: silicon photonics platform ePIXfab,Electronics Letters (invited), 45(12), p.581-582 (2009)

S. Selvaraja, P. Jaenen, W. Bogaerts, P. Dumon, D. Van Thourhout, R. Baets, Fabrication of Photonic Wire and Crystal Circuits in Silicon-on-Insulator Using 193nm Optical Lithography,Journal of Lightwave Technology, 27(18), p.4076-4083 (2009) 


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