All-fiber fundamentally mode locked 12 GHz laser comb for stable microwave generation

We have developed a compact, yet very stable all-fiber fundamentally mode-locked 12 GHz laser system. The passively mode-locked laser centered at 1535 nm has temporal bandwidth of ~2 ps, average power of 3mW and timing jitter of 44 fs/pulse.

The development of frequency combs has dramatically improved the precision and accuracy of optical frequency metrology. Frequency combs can determine optical frequency values eight orders of magnitude more accurately than the best commercially available systems [1]. Laser sources with multi-gigahertz repetition rates at optical communications wavelengths are a critical building block for numerous applications such as frequency metrology and optical atomic clocks [2], optical arbitrary waveform generation [3], high speed optical communications [4], and the calibration of astrophysical spectrographs [5]. Frequency comb technology based on low noise and high repetition rate lasers is now being extensively studied to generate microwave signals [6], [7]. The main advantage of this approach to generate microwaves over commercial counterparts is the versatility, portability, and unprecedented precision in the fractional frequency stability at both long term and short term time scales. Several different approaches have been reported, most of which require a low jitter, picosecond and even femtosecond mode-locked laser with high repetition rates as the laser source. A hybrid integrated or fully integrated approach is desired to provide stability, low timing jitter, and compact footprint. Here, we demonstrate, for the first time, an all-fiber based compact, fundamentally mode-locked 12 GHz picosecond laser system with low timing jitter.