Continuously tunable slow-light device consisting of heater-controlled silicon microring array

We experimentally demonstrate a tunable slow-light device consisting of all-pass Si microrings. A compact device of 0.014 mm^2 footprint is fabricated by using CMOS-compatible process, and its center wavelength, bandwidth and delay are continuously tuned by integrated heaters. The tuning range is 300ps at fixed wavelengths with a 1nm bandwidth. Eye opening of 40Gbps non-return-to-zero signals is observed at up to a 150ps delay and a 4 bit buffering capacity is confirmed, which corresponds to a spatial buffering density of 0.29 kbit/mm^2