V-band ultra-fast tunable thin-film lithium niobate Fourier-domain mode-locked optoelectronic oscillator

We demonstrate the first Fourier-domain mode-locked optoelectronic oscillator (FDML OEO) fabricated on the thin-film lithium niobate (TFLN) platform, deploying an electrically tuned ultra-fast frequency-scanning filter, thanks to the high-speed Pockels effect in TFLN. Record-breaking high radiofrequency oscillations up to 65 GHz are achieved, with a phase noise more than 14 dB less at 50 GHz than that of a high-performance commercial signal source at an offset frequency of 10 kHz away from the carrier. A linearly chirped microwave waveform with an unprecedented scanning bandwidth of 30 GHz, corresponding to an impressive chirp rate of 5.7 GHz/μs and a large time-bandwidth product of 159054, is successfully generated by the FDML OEO. These results validate the feasibility of utilizing TFLN to fabricate integrated FDML OEOs capable of delivering ultra-wide scanning bandwidth at chirp rates and frequencies not attainable with any other approaches to date.