Broadband photocarrier dynamics and nonlinear absorption of PLD-grown WTe2 semimetal films

Abstract

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.

2D Layered Materials: Synthesis, Nonlinear Optical Properties, and Device Applications

“…In addition, the two‐photon absorption response of WS 2 and WSe 2 films was also discovered, as shown in Figure d–f. Recently, more TMDCs including MS 2 , MSe 2 , MTe 2 , have been also deeply studied. These explorations lay a foundation for their applications in nonlinear photonics.…”

“…Driven by these efforts, mode‐locked fiber lasers based on other layered TMDCs and their derivatives including MoSe 2 , MoTe 2 , WTe 2 , WSe 2 , MoSe 2 , SnS 2 , ReS 2 , In 2 Se 3 , InS, TiS 2 , PtS 2 , PtSe 2 , and HfS 2 , have also developed rapidly, as shown in Table . It can be seen that for these lasers, the minimum pulse width is 67 fs, maximum output power is 212 mW, and maximum repetition rate is 8.82 GHz .…”

An Insightful Picture of Nonlinear Photonics in 2D Materials and their Applications: Recent Advances and Future Prospects

“…Also, thulium mode‐locked fiber laser confirms the SA in WTe 2 . [ 350 ] TDSMs Cd 3 As 2 thin film shows excellent SA effect at 1, 1.5, and 2 µm by using thulium mode‐locked fiber laser. [ 351 ] TaAs is a member of TMMPs having inversion‐breaking of polar metals crystals, which caused spontaneous polarization.…”

Saturable Absorption in 2D Nanomaterials and Related Photonic Devices

“…Graphene dispersed in CHP was measured to have SA response from the visible to mid‐infrared region, and the SA of graphene deposited on quartz covered the microwave region . Most layered TMDs mainly show SA behavior in the visible and near‐infrared regions, while semimetal WTe 2 shows response in the mid‐infrared region . The I S for bulk WTe 2 at 1.55 µm is 64.6 W .…”