Ultrafast photonics applications based on evanescent field interactions with 2D molybdenum carbide (Mo2C)

Abstract

MXenes have attracted considerable attention for the generation of ultrafast pulsed lasers because of light–matter interactions and excellent saturable absorption characteristics. As a recently developed new member of the MXene family, two-dimensional (2D) molybdenum carbide (Mo₂C) exhibits outstanding optical properties. In this study, we synthesized Mo₂C nanosheets by using a liquid-phase exfoliation method and studied the nonlinear optical properties of Mo₂C nanosheets. The saturation intensity and the modulation depth were measured to be 200 MW cm⁻² and 5.1%, respectively. Moreover, we prepared a mode-locker based on a D-shaped fibre Mo₂C saturable absorber (SA) by employing evanescent field interactions. By implementing a D-shaped Mo₂C SA into ytterbium-doped and erbium-doped fibre lasers, highly stable mode-locked fibre lasers were demonstrated at the 1 micron and 1.5 micron scales, respectively. A pulse duration as short as 290 fs was obtained in the telecommunication window. The corresponding pulse energy and peak power were 0.86 nJ and 2982 W, respectively. Furthermore, a highly stable picosecond-pulse ytterbium-doped fiber laser with a maximum pulse energy of 0.38 nJ was achieved. Compared to recently reported studies based on Mo₂C, our experimental results are more advantageous. Our work indicates that a D-shaped Mo₂C SA can be used as a broadband mode-locker for potential applications in ultrafast photonics.