Recent advances in optoelectronic oscillators and quantum microwave photonics

An optoelectronic oscillator (OEO) is a representative microwave photonic system with a closed optoelectronic feedback loop to produce highly stable microwave signals. In addition to the generation of ultra-low phase noise single-frequency microwave signals based on narrowband filters, several novel mode-control schemes have been proposed and demonstrated recently for the generation of single-frequency and other types of microwave signals. Chip-scale integration of OEOs has also been demonstrated to further reduce its size and power consumption. As an emerging research field, quantum microwave photonics has also been explored very recently to boost the performance of traditional microwave photonic systems by harnessing the advantages of quantum technology, such as high sensitivity and wide processing bandwidth. Here we review recent advances in OEOs and quantum microwave photonics, including Fourier domain mode-locked OEO, parity-time symmetric OEO, optoelectronic parametric oscillator, broadband random OEO, photonic integrated OEO and quantum microwave photonic systems for signal detection, processing and sensing.