In-fibre second-harmonic generation with embedded two-dimensional materials

Silica-based optical fibres are a workhorse of nonlinear optics, providing ready access to a range of nonlinear phenomena including solitons and self-phase modulation. However, they have one fundamental limitation: due to the amorphous nature of silica, they do not exhibit second-order nonlinearity, except for negligible contributions from surfaces. Here we demonstrate second-harmonic generation in functionalized optical fibres by using a monolayer of highly nonlinear MoS 2 directly grown on the fibre’s core. The MoS 2 -functionalized fibre exhibits a second-order susceptibility ( χ (2) ) value of 44 pm V –1 and a second-harmonic generation conversion efficiency of 0.2 × 10 –3 m −2 W −1 . This approach is scalable and can be generalized to other transition metal dichalcogenides and a wide range of waveguide systems. Our results demonstrate a new approach towards efficient in-fibre second-harmonic generation sources and may establish a platform for χ (2) -based nonlinear fibre optics, optoelectronics, photonics platforms, integrated optical architectures and active fibre networks.