Few-Layer Platinum Diselenide as a New Saturable Absorber for Ultrafast Fiber Lasers.

A multilayer platinum diselenide (PtSe2) film was experimentally demonstrated as a new type of saturable absorber with the capability to deliver robust dissipative solitons in a passively mode-locked fiber laser. The PtSe2 film synthesized by chemical vapor deposition was placed onto the ferule of a single mode optical fiber through a typical dry transfer process. The nonlinear optical measurements reveal efficient saturable absorption characteristics in terms of a large modulation depth (26%) and low saturable intensity (0.346 GW cm-2) at the wavelength of 1064 nm. An all-fiber ring cavity was built, in which the PtSe2 film was sandwiched between two ferules as the saturable absorber and Ytterbium-doped fiber was used as the optical gain medium. Robust dissipative soliton pulses with a 3 dB spectral bandwidth of 2.0 nm and a pulse duration of 470 ps centered at 1064.47 nm were successfully observed in the normal dispersion regime. Moreover, our mode-locked lasers also exhibit good long-term stability. Our finding suggests that multilayer PtSe2 may find potential applications in nonlinear optics and ultrafast photonics.