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 MoS₂ directly grown on the fibre’s core. The MoS₂-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.

二氧化硅基光纤是非线性光学的主力军，可随时访问包括孤子和自相位调制在内的一系列非线性现象。然而，它们有一个基本限制：由于二氧化硅的无定形性质，它们不表现出二阶非线性，除了表面的贡献可以忽略不计。在这里，我们通过使用直接生长在光纤芯上的高度非线性 MoS ₂单层来演示功能化光纤中的二次谐波产生。MoS _{2官能化纤维表现出44 pm V} ^-1的二阶磁化率( χ ⁽²⁾ ) 值和0.2 × 10 ^-3  m ^-2的二次谐波产生转换效率 W ^-1。这种方法是可扩展的，可以推广到其他过渡金属二硫化物和广泛的波导系统。我们的结果展示了一种高效的光纤内二次谐波产生源的新方法，并可能为基于χ ⁽²⁾的非线性光纤、光电子学、光子学平台、集成光学架构和有源光纤网络建立平台。