Flexible embedded active optical link (original) (raw)

The increasing demand and use of optical fibers for sensor-applications and the increasing use of short distance optical communication on backplanes has been witnessed because of their many advantages. The work described in this paper provides a technology platform to increase the integration and compactness of these optical applications. We present the establishment of a bendable package of optical interconnections and opto-electronic components. Standard commercially available GaAs VCSEL's and GaAs photodetectors are thinned down to a thickness of 30 µm and embedded into a stack of cladding-, core-and Polyimide layers. Multimode waveguides are patterned in the core layer to connect the VCSEL and photodiode array's. Laser ablated 45 degrees micro-mirrors couple the light from the embedded opto-electronic components into-and out of the waveguides. The final layer-stack with embedded active optical interconnections is highly flexible and shows no warpage due to a symmetrical layer build-up. Galvanic fan-out of the contact pads of the VCSEL's and PD's is realized by laser ablated via's and sputtered copper tracks in between the layers. The stand-alone optical foil is only 160 µm thick and can reach a minimum bending radius of 0.5 cm. Optical bending losses of the flexible waveguides are lower than 0.25 dB per cm for a 8 mm bending radius at a wavelength of 850 nm.