  Instantaneous frequency measurement (IFM) of microwave signals is a
fundamental functionality for applications ranging from electronic warfare to
biomedical technology. Photonic techniques, and nonlinear optical interactions
in particular, have the potential to broaden the frequency measurement range
beyond the limits of electronic IFM systems. The key lies in efficiently
harnessing optical mixing in an integrated nonlinear platform, with low losses.
In this work, we exploit the low loss of a 35 cm long, thick silicon waveguide,
to efficiently harness Kerr nonlinearity, and demonstrate the first on-chip
four-wave mixing (FWM) based IFM system. We achieve a large 40 GHz measurement
bandwidth and record-low measurement error. Finally, we discuss the future
prospect of integrating the whole IFM system on a silicon chip to enable the
first reconfigurable, broadband IFM receiver with low-latency.
