Widely tunable Ka-band optoelectronic oscillator integrated on thin film lithium niobate platform

We report a novel widely tunable Ka-band optoelectronic oscillator (OEO) realized by integrating a Mach–Zehnder modulator (MZM), a thermally-tunable add-drop micro-ring resonator (MRR), and a Mach–Zehnder interferometer (MZI) on the thin film lithium niobate platform, with the MZM and the MRR sequentially situated in one of the MZI arms. The MZM is for modulating the optical carrier, while the add-drop MRR is for selecting a single modulation sideband to beat with the unmodulated optical carrier from the other arm of the MZI, such that the OEO oscillation frequency is determined by the frequency spacing between the optical carrier and the selected modulation sideband, while the frequency tuning range is determined by the free spectral range of the MRR. By tuning the resonances of the add-drop MRR, the oscillation frequency can be tuned from 20 to 35 GHz, with the phase noises of −85 dBc/Hz @10 kHz and −116 dBc/Hz @100 kHz in the whole tuning range, which represent much higher oscillation frequency, much wider frequency tuning range, and lower phase noise than those of the photonic integrated OEOs realized with other material platforms reported previously.