Demonstration of Enhanced Saturable Absorption in Upconverter Integrated MoS 2 Heterostructure Thin Film Using Nanopulsed Green Laser

Upconverter/MoS 2 heterostructure thin films fabricated by hydrothermal technique are confirmed by X‐ray diffraction and Raman studies. Field‐emission scanning electron microscopy (FESEM) and high‐resolution transmission electron microscopy (HRTEM) reveal the nanobelt structured MoS 2 mingled with trapezoid structure fluoride upconverters and sphere‐shaped oxide upconverters. The films exhibit green () and red () emission. The influence of upconverters on the nonlinear absorption of MoS 2 is exploited by Z‐scan technique using nanopulsed laser. Estimated ground‐state absorption cross section is higher than the excited‐state absorption cross section of the samples and it confirms the occurrence of saturable absorption. CeO 2 :Yb,Er@MoS 2 exhibits stronger saturable absorption due to synergetic effects like higher linear absorption coefficient at 532 nm, stronger green emission, and reduced size. Results pave way for the design of optical switches, Q‐switches, and mode lockers using upconverter integrated MoS 2 thin films.