Publication Details

Gao, W., Huang, L., Xu, J., Chen, Y., Zhu, C., Nie, Z., Li, Y., Wang, X., Xie, Z., Zhu, S., Xu, J., Wan, X., Zhang, C., Xu, Y., Shi, Y. & Wang, F. (2018). Broadband photocarrier dynamics and nonlinear absorption of PLD-grown WTe2semimetal films. Applied Physics Letters, 112 (17), 17112-1-17112-5.


WTe 2 is a unique material in the family of transition metal dichalcogenides and it has been proposed as a candidate for type-II Weyl semimetals. However, thus far, studies on the optical properties of this emerging material have been significantly hindered by the lack of large-area, high-quality WTe 2 materials. Here, we grow a centimeter-scale, highly crystalline WTe 2 ultrathin film (∼35 nm) by a pulsed laser deposition technique. Broadband pump-probe spectroscopy (1.2-2.5 μm) reveals a peculiar ultrafast optical response where an initial photo-bleaching signal (lasting ∼3 ps) is followed by a long-lived photoinduced absorption signature. Nonlinear absorption characterization using femtosecond pulses confirms the saturable absorption response of the WTe 2 ultrathin films, and we further demonstrated a mode-locked Thulium fiber laser using a WTe 2 absorber. Our work provides important insights into linear and nonlinear optical responses of WTe 2 thin films.

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