Tungsten diselenide for mode-locked erbium-doped fiber lasers with short pulse duration.

In this paper, a WSe film prepared by chemical vapor deposition (CVD) is transferred onto a tapered fiber, and a WSe saturable absorber (SA) is fabricated. In order to measure the third-order optical nonlinearity of the WSe, the Z-scan technique is applied. The modulation depth of the WSe SA is measured as being 21.89%. Taking advantage of the remarkable nonlinear absorption characteristic of the WSe SA, a mode-locked erbium-doped fiber laser is demonstrated at 1557.4 nm with a bandwidth of 25.8 nm and signal to noise ratio of 96 dB. To the best of our knowledge, the pulse duration of 163.5 fs is confirmed to be the shortest compared with previous mode-locked fiber lasers based on transition-metal dichalcogenides SAs. These results indicate that WSe is a powerful competitor in the application of ultrashort pulse lasers.