Preparation of topological crystalline insulator SnTe thin films for application of saturable absorber

A series of topological insulators (TIs) based saturable absorbers (SAs), e.g., Bi2Se3, Bi2SeTe2, and Bi4Br4, are confirmed to exhibit excellent non-linear optical response due to the topological edge states. Here, we demonstrate how a topological crystalline insulator, SnTe thin films, can be prepared on highly oriented pyrolytic graphite and gold-plated mirrors through molecular beam epitaxy. SnTe-SAs incorporated into Er-doped fiber lasers exhibit a large modulation depth of 27.2% and accomplish mode-locking at 1558 nm with a pulse width of 319 fs, indicating preeminent nonlinear optical performance among the reported TI-based SAs. This work illuminates the preparation of SnTe thin films and demonstrates the great potential of SnTe films in ultrafast optical devices.