All-fiber photonic, ultralow-noise, robust optical and microwave signal generators for FELs and UED

Abstract

Optical timing and synchronization is becoming a more important and essential element for ultrafast X-ray and electron science. As a result, compact, ultralow-noise, mechanically robust and long-term stable optical and microwave signal generators are highly desirable for future XFELs and UEDs. Here we show that the combination of mode-locked fiber laser and fiber delay-based stabilization method enables the generation of ultralow-noise optical and microwave signals. We show that all-PM fiber lasers can provide excellent mechanical robustness: stable laser operation over >1 hour is maintained even in continuous 1.5 g vibrations [1]. Using a compactly packaged fiber delay as the timing reference, we could stabilize the repetition-rate phase noise of mode-locked lasers down to -100 dBc/Hz and -160 dBc/Hz at 1 Hz and 10 kHz offset frequency, respectively, at 1 GHz carrier, which corresponds to only 1.4 fs rms absolute timing jitter [1 Hz - 100 kHz] [2]. With DDS-based electronics, low-noise and agile microwave frequency synthesizer was also realized [3]. This new class of photonic signal generator will be suitable for master oscillators in various accelerator-based light sources.