Near‐Surface Buried Plasmonic Nanoparticles in Glass as Novel Nonlinear Saturable Absorbers for Ultrafast Lasers

Abstract Ultrafast lasers play important roles for scientific research and industrial applications. Saturable absorbers serve as crucial components for ultrafast laser generation. For decades, securing saturable absorbers with superior performance is one of the focuses in the field of advanced laser technology. In this work, the authors fabricate a new saturable absorption mirror (SAM) based on BK7 glass wafer, which is with a buried thin‐layer of silver (Ag) nanoparticles (NPs). The embedded Ag NPs‐based SAM (Ag‐NPs‐SAM) possesses excellent saturable absorption features due to the localized surface plasmon resonance (LSPR) effect of Ag NPs, and outstanding environmental stability owing to the protection of insulating dielectrics. In addition, benefiting from the ultrafast recovery time of Ag NPs, a continuous‐wave mode‐locking operation with the embedded Ag‐NPs‐SAM at 1037 nm is achieved in a Yb:KGW solid‐state laser system, obtaining pulses of a duration as short as 324 fs. The authors work offers a new strategy toward broadband response and high‐stability saturable absorbers for developing advanced ultrafast lasers.