Oct. 8, 2008 – European R&D consortium IMEC says it has made first functional optical links embedded in a flexible substrate, paving the way toward optical sensing foils for use in monitoring irregular or moving surfaces.
Integrated optical interconnections are highly sensitive, but are insensitive to electromagnetic interference and are applicable in harsh environments. IMEC previously achieved embedded optical links on rigid surfaces last year. Its new work advances on this, by thinning standard GaAs photodetectors and VCSELs (vertical-cavity surface-emitting laser) down to 30μm and embedding them into a flexible foil of optical transparent material, and optically coupling them with embedded waveguides and out-of-plane micromirrors. IMEC says the resulting structure “shows good adhesion and flexible behavior.”
IMEC is looking to extend this technology into two types of sensors, array waveguide and optical fiber, both of which can be used for sensor foils. The former relies 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 pressure is applied to the foil the distance between the waveguides decreases and light is transmitted from one layer to the other. This is a low-cost sensor suited for high-density pressure sensors on small areas, IMEC notes.
The other type of sensor, optical sensing foils, combine integrated optical interconnections and flexible, stretchable electronics, to create a “skin-like” foil sensitive to touch, pressure, or deformation, with applications in medicine and industry. IMEC is currently working on this technology with partners in the EC’s 7th Framework project PHOSFOS (Photonic Skins For Optical Sensing) to develop photonic foils based on optical sensors.