On-chip two-step microwave frequency measurement with high accuracy and ultra-wide bandwidth using add-drop micro-disk resonators.

An on-chip two-step microwave frequency measurement method with high accuracy and an ultra-wide frequency measurement range is reported. A silicon photonic integrated micro-disk resonator (MDR) array is used to coarsely measure the signal frequency via an array of add-drop MDRs with smaller disk radii; then an MDR with a larger radius is used to finely measure the signal frequency, which is done by monitoring the optical powers of the optical signals from the through port and drop port of the MDRs. The proposed system features a very compact structure, ultra-wide frequency measurement range, and high frequency measurement accuracy, which is verified by a proof-of-concept experiment using two MDRs with radii of 6 and 10 μm. A frequency measurement of microwave signals from 1.6 to 40 GHz is implemented with a measurement error of less than 60 MHz. The stability of the system is also evaluated.