Reconfigurable optical beamformer with graphene-based fine-tunable optical delay line

An integrated graphene-based fine-tunable optical delay line in silicon nitride has been designed. A high optical delay time up to 920 ps has been calculated with a device footprint A ~ 4 mm2. The device includes two graphene-based Mach-Zehnder interferometer (MZI) switches and two vertically-stacked microring resonators. Graphene capacitors have been integrated in the optical delay line to exploit the electro-optic effect aiming at fast tuning (response time of few nanoseconds) with a low power dissipation. Such performance, together with optical loss α < 27 dB, makes this device suitable for beam-steering up to 20 radiating elements, with an angle of ±20° in the azimuth direction, of a tile in a phased-array antenna included in an X-band SAR.