Flexible waveguides could be used for data sensors

The first functional optical links embedded in a flexible substrate have been demonstrated at INTEC, a lab associated with IMEC based at Ghent University

The links could be used as optical waveguides, light sources, and pressure sensors.

IMEC reported embedded optical links on rigid surfaces last year. The current research takes opto-electronics a step further.
Commercially available GaAs photo-detectors and GaAs vertical-cavity surface-emitting laser are thinned down to 30µm, and embedded into a flexible foil of optical transparent material. They are then optically coupled with embedded waveguides and out-of-plane micromirrors. The resulting structure shows good adhesion and is flexible.

IMEC is using the technology in two types of sensors: array waveguide sensors and optical fibre sensors. Both can be used for sensor foils. Array waveguide sensors rely on the change in coupling between arrays of crossing waveguides. Two layers of polymer waveguides are separated by a thin layer of soft silicone. When no pressure is applied, no crosstalk is detected. But when pressure is applied to the foil, the distance between the waveguides in the separated layers decreases, and light is transmitted from one layer to the other. This low-cost sensor is ideally suited for high-density pressure sensors on small areas.

Optical sensing foils combine integrated optical interconnections, and flexible, stretchable electronics. The researchers want to create a flexible and stretchable skin-like foil sensitive to touch, pressure, or deformation. A 7th Framework project known as PHOSFOS, for Photonic Skins For Optical Sensing, is develop photonic foils based on optical fibre sensors. These could be used in civil engineering and medicine, or in monitoring the integrity of machine parts such as helicopter blades.

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