In this paper, we propose a four-wave mixing-based photonic crystal fiber (PCF) microfluid sensor, and two U-shape microslits fabricated by a femtosecond laser are embedded into the sensor for real-time microfluid measurement. Theoretical and experimental results prove that the signal wavelength is sensitive to both the refractive index (RI) and the material dispersion property of the liquid sample filled into the air channels. For different aqueous target samples at low concentrations, the responses of signal wavelength are consistent with each other. The obtained RI sensitivity is approximately 881.36 nm/RIU, and the sensing resolution is around 1.6 × 10⁻⁴ RIU. The proposed sensor also shows a better figure of merit (FOM) as high as 313.65 RIU⁻¹ when compared with the fiber SPR sensors. Besides, the signal wavelengths present different responses with the increasing aqueous concentration due to the separated dispersion characteristics of the filled liquid samples, which can be potentially applied for the discrimination of liquid samples with a well-designed wavelength-coded sensor array in the future.

中文翻译：

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嵌入式U形微缝隙的基于四波混合的光子晶体光纤微流体传感器

在本文中，我们提出了一种基于四波混合的光子晶体光纤（PCF）微流体传感器，并将飞秒激光制造的两个U形微缝隙嵌入到传感器中以进行实时微流体测量。理论和实验结果证明，信号波长对填充到空气通道中的液体样品的折射率（RI）和材料色散特性均敏感。对于低浓度的不同含水目标样品，信号波长的响应彼此一致。所获得的RI灵敏度约为881.36nm / RIU，并且感测分辨率为1.6×10 ^-4 RIU左右。拟议的传感器还显示了高达313.65 RIU ^-1的更好品质因数（FOM）与光纤SPR传感器相比。此外，由于填充的液体样品的分离的色散特性，信号波长随着水浓度的增加呈现出不同的响应，这在将来可以通过设计良好的波长编码传感器阵列潜在地应用于液体样品的判别。