High-isolation microwave photonic sub-harmonic mixer

A microwave photonic sub-harmonic mixer with a wide bandwidth, high RF-to-LO isolation and high RF/LO-to-IF isolation is presented. High isolation between the RF port and the LO port is obtained by separately applying the RF signal and the LO into two Mach Zehnder modulators, which are far apart, inside an integrated four-parallel Mach Zehnder modulator to avoid crosstalk between signal electrodes. High isolation between the RF/LO port and the IF port is obtained by designing the bias voltages of the modulator to largely suppress the optical carrier. Experimental results demonstrate sub-harmonic frequency mixing operation with > 38 dB LO-to-IF isolation, > 40 dB RF-to-LO isolation and > 5 dB conversion efficiency for an input RF signal frequency range of 0.5-40 GHz.