Alternately Intercalated Heterostructures of Carbon and MoS2 Monolayers as Saturable Absorber for Ultrashort Femtosecond Mode-Locked Lasers

2D van der Waals (VDWs) heterostructures have attracted much attention due to their exotic electronic and optical properties, which provide a new platform for material science and device fabrication. In this work, by coupling atomic interface engineering, an alternately intercalated superstructure of carbon and MoS 2 monolayers (m-C/MoS 2 ) is designed as a novel saturable absorber (SA) for mode-locked ultrafast laser generation. The novel intercalated structures exhibit excellent properties including wide bandgap, fast inter- and intra-band carrier relaxation time, and superior saturable absorption characteristic, etc. Consequently, a continuous wave mode-locked Yb:CALGO bulk laser with pulse width as short as 92 fs is achieved by using the prepared m-C/MoS 2 SA mirror, which is much shorter than those obtained with other reported 2D materials. This study provides a valuable strategy for the development of ultrashort pulse femtosecond lasers. The novel VDWs heterostructures also open new avenues toward advanced photonic devices.