Third-Order Nonlinear Optical Response of Few-Layer MXene Nb2C and Applications for Square-Wave Laser Pulse Generation

Niobium carbide (Nb2C), a newly developed 2D MXene material, has attracted much attention due to its outstanding electronic and optical properties. In this work, few-layer 2D Nb2C nanosheets are synthesized by magnetron sputtering deposition method. Z-scan measurements with pump source operating at 1.0 mu m are performed to study the third-order nonlinear optical response, revealing excellent light modulation capabilities of 2D Nb2C. The effective nonlinear absorption coefficient (beta(eff) approximate to -10(5) cm GW(-1)) caused by saturable absorption effect is determined to be two orders of magnitude larger than that induced by reverse saturable absorption processes (two-photon absorption, etc.). The positive nonlinear refractive index n(2) is determined to be approximate to 10(-13) m(2) W-1 for the first time. Moreover, by decorating 2D Nb2C onto microfiber, microfiber-based 2D Nb2C saturable absorber is fabricated and applied for compact square-wave pulse mode-locking ytterbium-fiber laser. The pulse duration of SWP increases from 0.652 to 1.616 ns with the pulse energy increasing linearly up to 0.89 nJ while the peak power remains a constant. The results not only verify the capability of 2D Nb2C as an optical modulator, but also pave a new way for exploring SWP laser sources.

Automated summary

In this study, few-layer 2D Nb2C nanosheets were synthesized and demonstrated to have excellent light modulation capabilities and nonlinear optical response, showing potential for applications as optical modulators. By fabricating a microfiber-based 2D Nb2C saturable absorber, it was successfully applied for compact square-wave pulse mode-locking ytterbium-fiber laser, showcasing new possibilities for SWP laser sources.