Silicon nanophotonic spectral translator facilitates detection of mid-infrared signals for sensing applications

(PresseBox) (Leuven, ) INTEC, imec's associated lab at Ghent University, in collaboration with Columbia University and IBM TJ Watson Research Center (US), has demonstrated efficient up-conversion of mid-infrared signals into the telecom band by means of four-wave mixing in a Si optical waveguide. With this spectral translator, smaller, lighter and more highly integrated mid-infrared optical systems can be developed for a variety of applications. This work has recently been published in Nature Photonics.

The researchers used efficient four-wave mixing in silicon nanophotonic wires to enable spectral translation of a signal at 2,440nm to the telecom band at 1,620nm, across a span of 62THz. This allows detecting weak mid-infrared signals with uncooled, high-sensitivity, high-speed photodetectors developed for telecommunication applications. This is a stepping-stone towards the development of high-sensitivity mid-infrared spectroscopic sensing systems fully integrated on a silicon waveguide circuit. Such systems can find applications in e.g. industrial and environmental monitoring, threat detection, medical diagnostics and free-space communication.

The 2-cm-long silicon nanophotonic wire used here for spectral translation was fabricated on a 200mm silicon-on-insulator (SOI) wafer at imec, using the multi-project-wafer service ePIXfab (www.ePIXfab.eu). The entire length of the wire is coiled into a compact spiral, occupying an on-chip footprint of only 625µm x 340µm.

The large spectral translation over more than 62THz illustrates that the methodology applied here can be used to efficiently convert optical information on a mid-infrared carrier into the telecom band. Without such a spectral translator, detection of mid-infrared signals is more difficult. It then relies on the use of narrow-bandgap semiconductors that require cooling for their operation, restricting the development of compact, low-power integrated mid-infrared systems. The proposed silicon nanophotonic spectral translator, on the contrary, can easily be integrated with the numerous mid-infrared Si components demonstrated to date, including waveguides, vertical grating couplers, microcavities and electrooptic modulators. Altogether, these components have the potential to produce flexible, chip-scale optical systems for mid-infrared applications.

This work has been published in Nature Photonics, http://www.nature.com/.... The key researcher at INTEC is ir. Bart Kuyken, a PhD student supervised by Gunther Roelkens and Roel Baets.

The result is obtained in the framework of two European Research Council grants, MIRACLE and InSpectra, and was achieved through a collaboration with Columbia University and IBM TJ Watson Research Center in New York, USA.

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