Enhanced ultrafast dynamics and saturable absorption response of Nb2SiTe4/graphene heterostructure for femtosecond mode-locked bulk lasers

Abstract

Two-dimensional (2D) heterostructure provides a promising opportunity to create new hybrid materials with unique tailored properties for novel electronic and photonic devices. Here, 2D Nb2SiTe4/Graphene (NST/G) heterostructure samples with different thicknesses of Nb2SiTe4 are fabricated by mechanical exfoliation and dry transfer methods. Their photocarrier dynamics and nonlinear optical responses are systematically investigated by pump–probe and Z-scan measurements. The results illustrate that Graphene acts as an electron transfer channel effectively shortening the photocarrier lifetime in NST. Moreover, the thinner of NST, the larger of the photocarrier recombination rate in NST/G heterostructure because of the high surface state density and strong electron–phonon coupling effect. Significantly, the 2D NST/G heterostructure with thinner NST also exhibits a larger nonlinear absorption coefficient and moderate saturable absorption parameters, which endow the high-performance passively mode-locked femtosecond laser. With 2 nm NST/G heterostructure as saturable absorber (SA), passively mode-locked Yb:KYW bulk laser is realized with the pulse width of 415 fs and output power of 498 mW. Our results pave a versatile way for designing desirable photonic devices and applications.