WS₂ based 523 MHz mode-locked erbium-doped fiber laser for microwave photonic application

Microwave photonics is an important application for mode-locked lasers and requires the lasers to have high repetition rate and relatively low timing jitter. Although many mode-locked lasers based on two-dimensional (2D) materials have been reported, their applications in high-quality microwave photonics have not been achieved yet. We demonstrate a linear-cavity mode-locked Erbium-doped fiber laser with tungsten disulfide (WS2) saturable absorber (SA). By optimizing the WS2 SA fabrication, SA with low loss and moderate modulation depth is obtained. The laser based on this WS2 SA is demonstrated to have a fundamental repetition rate of 523 MHz, a central wavelength of 1558.6 nm, a 3-dB bandwidth of 7.4 nm and a timing jitter of 28 fs. With this laser, microwave photonic application of frequency synthesis is obtained with a tuning range up to 10 GHz and an extinction ratio greater than 60 dB in the whole range. We believe this is the first work that utilizes a 2D material SA based mode-locked laser for high-quality microwave photonic applications. This work indicates the potential of 2D material SA for high-speed and high-precision photonic and microwave systems.