Photonically referenced extremely stable oscillator.

Due to their low phase noise at high carrier frequencies, photonic microwave oscillators are continuously expanding their application areas including digital signal processing, telecommunications, radio astronomy, and RADAR and LIDAR systems. Currently, the lowest noise photonic oscillators rely on traditional optical frequency combs with multiple stabilization loops that incorporate large vacuum components and complex optoelectronic configurations. Hence, the resulting systems are not only challenging to operate but also expensive to maintain. Here, we introduce a significantly simpler solution: a Photonically Referenced Extremely STable Oscillator (PRESTO). PRESTO requires only three key components: a femtosecond laser, a fiber delay element, and a pulse timing detector. The generated microwave at 10 GHz has phase noise levels of -125, -145, and <-160 dBc/Hz at 1, 10, and >100 kHz, respectively, with an integrated timing jitter of only 2 fs root mean square (RMS) over [100 Hz-1 MHz]. This approach offers a reliable solution for simplifying and downsizing photonic oscillators while delivering high performance.