The centrosymmetric nature of silica fibre precludes the realisation of second-order nonlinear processes in optical fibre systems. Recently, the integration of 2D materials with optical fibres has opened up a great opportunity to develop all-fibre active devices. Here, we demonstrate high-efficiency second-order nonlinear frequency conversions in an optical microfibre assisted with few-layer gallium selenide (GaSe) nanoflakes. Attributed to the strong evanescent field of the microfibre and ultrahigh second-order nonlinearity of the GaSe nanoflakes, second harmonic generation (SHG) and sum-frequency generation (SFG) are effectively achieved with only sub-milliwatt continuous-wave (CW) lasers in the wavelength range of 1500-1620 nm, covering the C and L telecom bands. The SHG intensity from the microfibre is enhanced by more than four orders of magnitude with the assistance of the GaSe nanoflakes on fibre nonlinear processes. Moreover, in the SFG process, the intensity transfer between different frequencies can be effectively manipulated by changing the wavelengths and powers of two pump lasers. The realised strong second-order nonlinearity in the GaSe-integrated microfibre might expand the applications of all-fibre devices in all-optical signal processing and new light source generation at awkward wavelengths.

中文翻译：

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借助多层GaSe辅助的光学微纤维中的高效二阶非线性过程。

石英纤维的中心对称性质阻止了光纤系统中二阶非线性过程的实现。最近，二维材料与光纤的集成为开发全光纤有源设备开辟了巨大的机会。在这里，我们展示了在具有几层硒化镓（GaSe）纳米薄片辅助的光学微纤维中的高效二阶非线性频率转换。归因于微纤维的强瞬逝场和GaSe纳米片的超高二阶非线性，仅在亚兆瓦级连续波（CW）激光器中有效地实现了二次谐波（SHG）和和频产生（SFG）。波长范围为1500至1620 nm，覆盖了C和L电信频段。在纤维非线性过程中，借助GaSe纳米薄片，微纤维的SHG强度提高了四个数量级以上。而且，在SFG工艺中，通过改变两个泵浦激光器的波长和功率，可以有效地操纵不同频率之间的强度传递。在集成GaSe的微纤维中实现的强二阶非线性可能会扩展全纤维设备在全光信号处理和尴尬波长下产生新光源方面的应用。