Integrated graphene-based semimetal/metallic-like MSe2 (M = Pt, Re) heterostructures for mid-infrared ultrafast photonics

Abstract

Mid-infrared (MIR) ultrafast photonics has received significant interest due to the development of compact and robust MIR laser sources capable of emitting wavelengths beyond 2 μm. Transition metal selenides (TMSes), with the properties of feasibly tunable bandgaps, desirable photocarrier transmission property, and broadband nonlinear optical response, have become a research focus on ultrafast photonic applications. However, the relatively large bandgap (around 1 eV) of the TMSes greatly restricts their applications in the MIR region. Here, the synergetic interaction between multilayer graphene (Gr) and semimetal or metallic-like (PtSe2 and ReSe2) is employed to tune the optical properties and to further optimize the optical performance of TMSes in the MIR region. Benefiting from the ultrafast photocarrier relaxation time, appropriate modulation depth, and almost zero non-saturated loss of Gr-PtSe2 and Gr-ReSe2 heterostructures, stable Q-switched laser operation at 1.9 μm has been achieved in an integrated design based on waveguide laser platform. The results demonstrate that combining the semimetal or metallic-like TMSes with van der Waals (vdW) heterostructures is a promising strategy to extend the photonic applications of TMSes into the MIR region, indicating the potential applications of graphene-based TMSes vdW heterostructures for MIR integrated photonics.