Optical fibres with embedded two-dimensional materials for ultrahigh nonlinearity
Initial tests show that the fabrication strategy of MoS2 is amenable to other transition metal dichalcogenides, making these embedded fibres versatile for several all-fibre nonlinear optics and optoelectronics applications.
Abstract
Nonlinear optical fibres have been employed for a vast number of applications, including optical frequency conversion, ultrafast laser and optical communication<sup>1-4</sup>. In current manufacturing technologies, nonlinearity is realized by the injection of nonlinear materials into fibres<sup>5-7</sup> or the fabrication of microstructured fibres<sup>8-10</sup>. Both strategies, however, suffer from either low optical nonlinearity or poor design flexibility. Here, we report the direct growth of MoS<sub>2</sub>, a highly nonlinear two-dimensional material<sup>11</sup>, onto the internal walls of a SiO<sub>2</sub> optical fibre. This growth is realized via a two-step chemical vapour deposition method, where a solid precursor is pre-deposited to guarantee a homogeneous feedstock before achieving uniform two-dimensional material growth along the entire fibre walls. By using the as-fabricated 25-cm-long fibre, both second- and third-harmonic generation could be enhanced by ~300 times compared with monolayer MoS<sub>2</sub>/silica. Propagation losses remain at ~0.1 dB cm<sup>-1</sup> for a wide frequency range. In addition, we demonstrate an all-fibre mode-locked laser (~6 mW output, ~500 fs pulse width and ~41 MHz repetition rate) by integrating the two-dimensional-material-embedded optical fibre as a saturable absorber. Initial tests show that our fabrication strategy is amenable to other transition metal dichalcogenides, making these embedded fibres versatile for several all-fibre nonlinear optics and optoelectronics applications.