Wu Kan, Zhang Xiaoyan, Wang Jun, Li Xing, Chen Jianping
Opt Express. 2015 May 4;23(9):11453-61. doi: 10.1364/OE.23.011453.
Two-dimensional (2D) nanomaterials, especially the transition metal sulfide semiconductors, have drawn great interests due to their potential applications in viable photonic and optoelectronic devices. In this work, 2D tungsten disulfide (WS2) based saturable absorber (SA) for ultrafast photonic applications was demonstrated. WS2 nanosheets were prepared using liquid-phase exfoliation method and embedded in polyvinyl alcohol (PVA) thin film for the practical usage. Saturable absorption was discovered in the WS2-PVA SA at the telecommunication wavelength near 1550 nm. By incorporating WS2-PVA SA into a fiber laser cavity, both stable mode locking operation and Q-switching operation were achieved. In the mode locking operation, the laser obtained femtosecond output pulse width and high spectral purity in the radio frequency spectrum. In the Q-switching operation, the laser had tunable repetition rate and output pulse energy of a few tens of nano joule. Our findings suggest that few-layer WS2 nanosheets embedded in PVA thin film are promising nonlinear optical materials for ultrafast photonic applications as a mode locker or Q-switcher.
二维（2D）纳米材料，尤其是过渡金属硫化物半导体，因其在可行的光子和光电器件中的潜在应用而备受关注。在这项工作中，展示了用于超快光子应用的基于二维二硫化钨（WS2）的可饱和吸收体（SA）。采用液相剥离法制备了WS2纳米片，并将其嵌入聚乙烯醇（PVA）薄膜中以供实际使用。在WS2-PVA SA中，在1550nm附近的电信波长处发现了可饱和吸收现象。通过将WS2-PVA SA引入光纤激光腔，实现了稳定的锁模操作和调Q操作。在锁模操作中，激光器在射频频谱中获得了飞秒输出脉冲宽度和高光谱纯度。在调Q操作中，激光器具有可调的重复频率和几十纳焦的输出脉冲能量。我们的研究结果表明，嵌入PVA薄膜中的几层WS2纳米片作为锁模器或调Q器，是用于超快光子应用的有前途的非线性光学材料。
