The layered two-dimensional (2D) materials, e.g., the well-known graphene, transition metal dichalcogenides, and topological insulators, have attracted great interest of researchers from fundamental research as well as industries owing to their intriguing properties in a number of aspects. In practical applications, the efficient modification of the features of 2D materials is compelling and essential to achieve desired functionalities. Ion implantation has been successfully applied to synthesize graphene. The most exotic advantage of ion beam technology is that it offers distinct options of energetic beams, which has recently shown the unique capability to modify and tailor the properties of versatile 2D materials. To name a few, the energetic ion beams could implement the surface morphology or layer-to-layer structural engineering of 2D materials. At the microcosmic level, the introduction of ion beam induced defects and intentional doping of specific ions are the basis of tailoring properties of 2D materials. By manipulating the parameters of ion beams (energies, species, fluences, incident angles, etc.), the modified 2D materials may possess novel properties, which are unprecedented in pristine ones. Promising applications based on these 2D materials with ion beam tailored features have been realized in a broad range of fields. In this work, we systematically review the latest research progress on the deployed techniques and property modifications of graphene and other 2D materials under the treatment of various ion beams. A few selected applications are presented to indicate the practical potentials of ion beam modified 2D materials in distinct areas. Perspectives on future developments are also provided by focusing on several promising topics.

The nonlinear optical responses of two-dimensional (2D) few-layer tin diselenide (SnSe₂) have been investigated in this work. By applying the Z-scan technique, the saturable absorption of SnSe₂ thin film has been observed at a wavelength of ~1μm, which enables SnSe_2, a new saturable absorber for pulsed laser generation. A detailed exploration of the nonlinear absorption of SnSe₂ film and their dependence on excitation pulse energy is carried out. Our results show that saturation intensity of the nonlinear absorption is ~23.78 GW/cm² and corresponding nonlinear absorption coefficients are at a range from −13596 to −2967.3 cm/GW. By employing the SnSe₂-coated mirror as a saturable absorber, the passively Q-switched lasing has been achieved on a crystalline waveguide platform at ~1 μm.

Spin–charge conversion is a spin–orbit coupling phenomena where electrical currents can generate transverse spin currents and vice versa. It is one of the central topics in spintronics and widely applied to manipulate the spin and charge degrees of freedom in materials. Previous research on spin–charge conversion was mainly carried out by transport measurements, which lies in the (quasi)equilibrium and DC/low-frequency limit. The recent development of THz emission spectroscopy applied to this field provides additional insights into the dynamics of the spin–charge conversion process, i.e., its ultrafast timescales. Here, the underlying physics and the latest progress of THz studies on spintronics are introduced. The technical details and some features of this technique are summarized, including spin current generation, signal detection, and data analysis. Finally, some possible developments are discussed as well as future research and applications.

We report on the operation of passively $Q$-switched waveguide lasers at 1 μm wavelength based on a $\mathrm{graphene}/{\mathrm{WS}}_2$ heterostructure as a saturable absorber (SA). The gain medium is a crystalline $\mathrm{Nd}\text{:}{\mathrm{YVO}}_4$ cladding waveguide produced by femtosecond laser writing. The nanosecond waveguide laser operation at 1064 nm has been realized with the maximum average output power of 275 mW and slope efficiency of 37%. In comparison with the systems based on single ${\mathrm{WS}}_2$ or graphene SA, the lasing $Q$-switched by a $\mathrm{graphene}/{\mathrm{WS}}_2$ heterostructure SA possesses advantages of a higher pulse energy and enhanced slope efficiency, indicating the promising applications of van der Waals heterostructures for ultrafast photonic devices.

Two-dimensional (2D) materials have generated great interest in the past few years opening up a new dimension in the development of optoelectronics and photonics. In this paper, we demonstrate 6.5 GHz fundamentally Q-switched mode-locked lasers with high performances in the femtosecond laser-written waveguide platform by applying graphene, MoS₂ and Bi₂Se₃ as saturable absorbers (SAs). The minimum mode-locked pulse duration was measured to be as short as 26 ps in the case of Bi₂Se₃ SA. The maximum slope efficiency reached 53% in the case of MoS₂ SA. This is the first demonstration of Q-switched mode-locked waveguide lasers based on MoS₂ and Bi₂Se₃ in the waveguide platform. These high-performance Q-switched mode-locked waveguide lasers based on 2D materials pave the way for practical applications of compact ultrafast photonics.

We demonstrate high-repetition-rate fundamentally Q-switched mode-locked Nd:YAG waveguide laser modulated by platinum diselenide (PtSe₂) saturable absorber. The laser operation platform is a femtosecond laser-written monolithic Nd:YAG waveguide, and the saturable absorber is large-area few-layer PtSe₂ that possesses relatively lower saturation intensity and higher modulation depth in comparison with graphene. With the superb ultrafast nonlinear saturable absorption properties of as-synthesized PtSe₂, the waveguide laser could operate at ~8.8 GHz repetition rate and ~27 ps pulse duration, while maintaining a relatively high slope efficiency of 26% and high stability with signal-to-noise ratio (SNR) up to 54 dB. Our work indicates the promising applications of laser-written Nd:YAG waveguides and atomically thin PtSe₂ for on-chip integration of GHz laser sources toward higher repetition rates and shorter pulse duration.