Watt-level ultrafast bulk laser with a graphdiyne saturable absorber mirror

Passively mode-locked red Pr:LiYF4 laser based on a two-dimensional palladium diselenide saturable absorber

We report a passively mode-locked Pr:LiYF₄ (Pr:YLF) visible laser using a palladium diselenide (PdSe₂) as a saturable absorber (SA) for the first time, to the best of our knowledge. The nonlinear optical properties of two-dimensional (2D) PdSe₂ nanosheets in the visible band were studied by the open-aperture Z-scan technique. The results indicate the significant saturable absorption properties of PdSe₂ nanosheets in the visible region. Furthermore, the continuous wave mode-locked (CWML) visible laser based on PdSe₂ SA was successfully realized. Ultrashort pulses as short as 35 ps were obtained at 639.5 nm with a repetition rate of 80.3 MHz and a maximum output power of 116 mW. The corresponding pulse energy was 1.44 nJ and peak power was 41.3 W. These results indicate that 2D PdSe₂ SA is a promising high stability passively mode-locked device for ultrafast solid-state visible lasers.

Nonlinear optical response of a monolayer WS2 and the application of a hundred-MHz nanosecond laser

High quality monolayer WS₂ was successfully fabricated by chemical vapor deposition method. The nonlinear optical response of monolayer WS₂ is demonstrated for the first time. Due to the relatively low modulation depth of 1.4% and saturable intensity of 68.6 kW/cm² of monolayer WS₂, a robust continuous-wave mode-locked (CWML) nanosecond laser with a repetition rate of 93.1 MHz is obtained. To the best of our knowledge, this is the highest repetition rate of nanosecond pulses generated from CWML lasers. This work provides an effective approach to obtaining nanosecond pulsed lasers with repetition rates of hundred-megahertz.

High-Quality Graphene-Based Tunable Absorber Based on Double-Side Coupled-Cavity Effect

Graphene-based devices have important applications attributed to their superior performance and flexible tunability in practice. In this paper, a new kind of absorber with monolayer graphene sandwiched between two layers of dielectric rings is proposed. Two peaks with almost complete absorption are realized. The mechanism is that the double-layer dielectric rings added to both sides of the graphene layer are equivalent to resonators, whose double-side coupled-cavity effect can make the incident electromagnetic wave highly localized in the upper and lower surfaces of graphene layer simultaneously, leading to significant enhancement in the absorption of graphene. Furthermore, the influence of geometrical parameters on absorption performance is investigated in detail. Also, the device can be actively manipulated after fabrication through varying the chemical potential of graphene. As a result, the frequency shifts of the two absorption peaks can reach as large as 2.82 THz/eV and 3.83 THz/eV, respectively. Such a device could be used as tunable absorbers and other functional devices, such as multichannel filters, chemical/biochemical modulators and sensors.