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Ghent University 2012-09-23
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Photonics Research Group publishes a paper in Nature Photonics about mid-infrared spectral translation in silicon waveguides

In this Nature Photonics publication1 (Nature Photonics 6, 667–671 (2012)) researchers from the Photonics Research Group  show that by using a nonlinear optical process in silicon optical waveguides, mid-infrared optical signals can efficiently be up-converted to the near-infrared wavelength range, where they can be detected using well-developed, high-sensitivity photodetectors. This is a stepping-stone towards the development of high-sensitivity mid-infrared spectroscopic sensing systems fully integrated on a silicon waveguide circuit.

While optical applications cover the full wavelength range from ultraviolet over the visible into the near-infrared, mid-infrared and far-infrared, the sensitive detection of this light becomes more difficult to achieve when the optical wavelength becomes longer. This limits the achievable sensitivity of sensor systems based on mid-infrared light beams interrogating a sample. In this paper we show that weak mid-infrared signals can efficiently be up-converted to a shorter wavelength by means of a nonlinear optical process (namely four-wave mixing) in a silicon optical waveguide2. This allows detecting the mid-infrared signals with very well developed high-sensitivity, high-speed photodetectors developed for telecommunication applications. This demonstration is a stepping-stone towards the realization of silicon optical chips implementing very sensitive optical sensing systems in the mid-infrared using the existing telecommunication technology base for the detection of the mid-infrared signal. This result was obtained in the framework of two European Research Council grants in the Photonics Research Group (Department of Information Technology) at Ghent University: MIRACLE (prof. Günther Roelkens) and InSpectra (prof. Roel Baets), and was obtained through a collaboration with Columbia University and IBM TJ Watson Research Center in New York, USA. 


2 fabricated through the silicon multi-project wafer service ePIXfab