Synergizing the low-phase noise characteristics of a dielectric resonator oscillator and a bichromatic Brillouin laser oscillator.

We introduce a method that synergistically combines the distinct phase noise profiles of a dielectric resonator oscillator (DRO) and bichromatic Brillouin laser oscillator (BBLO), for high spectral purity microwave generation. Typically, free-running DROs exhibit high-phase noise at low-frequency offsets but ultra-low-phase noise at high offsets. In contrast, BBLOs based on photonic devices demonstrate very low-phase noise at low offsets, yet they experience increased phase noise at higher offsets due to photodetector shot noise. By locking the DRO to a frequency-matching BBLO, our experiment combines the merits of both oscillators and generates X-band microwave with exceptional phase noise across the entire frequency offset range, reaching -93 dBc/Hz at 100 Hz offset and -171 dBc/Hz at 10 MHz offset.