基于亚波长尺寸微纳光纤的光热光谱NH_(3)检测  

Photothermal Spectroscopy NH3 Detection Based on a Microfiber with Sub-Wavelength Dimension

作　　者：邾毅 郭安波[1] 曾祥龙[1] Zhu Yi;Guo Anbo;Zeng Xianglong(Key Lab of Specialty Fiber Optics and Optical Access Network,Joint International Research Laboratory of Specialty Fiber Optics and Advanced Communication,Shanghai University,Shanghai 200444,China)

机构地区：[1]上海大学特种光纤与光接入网重点实验室,特种光纤与先进通信国际联合研究实验室,上海200444

出　　处：《光学学报》2023年第16期365-371,共7页Acta Optica Sinica

基　　金：上海市科学技术委员会资助项目(20JC1415700);国家自然科学基金(12274281);高等学校学科创新引智项目(111计划)(D20031)。

摘　　要：在通信波段研究了基于亚波长尺寸微纳光纤的光热光谱气体传感技术,利用锥腰直径为1μm的微纳光纤代替传统的自由空间光气室和空芯光纤实现紧凑的全光纤结构,其引导的倏逝场被气体吸收后会激发光热效应。仿真结果表明,约25%的光波以倏逝场的形式沿光纤表面传播,可提供的光热效应强度约为空芯光纤的187倍。通过外差干涉法在微纳光纤提供的4 mm超短有效传感光程上实现了1512.24 nm处10^(-6)级别氨气(NH3)检测。当使用的泵浦光功率为3.6 mW时,得到1σ噪声等效检测下限为39×10^(-6),30个泵浦调谐周期内探测信号的不稳定性小于0.5%。Objective Gas sensing technology based on spectral absorption has been widely employed in various domains,such as industrial manufacturing and biomedical applications.Nevertheless,due to the constraints imposed by the Lambert-Beer law,the detection of weakly absorbing gases(such as ammonia)in the near-infrared(NIR)bands often necessitates the auxiliary utilization of multi-pass cells with ultra-long optical paths.This inevitably brings about a significant increase in equipment size and substantial manufacturing and operational costs.In recent years,it has been discovered that the photothermal spectroscopy(PTS)technique can compensate for the limitations of conventional spectral absorption-based gas sensing technologies,leading to extensive studies in this field.PTS adopts a pump-probe dual-light configuration,and the photothermal effect(PTE)induced by the non-radiative relaxation of gas molecules encodes the pump-light power variation onto the phase of the probe light.Subsequently,the phase fluctuation is extracted through a heterodyne or homodyne interferometer,and harmonic signals are demodulated through a lock-in amplifier.The PTE intensity(probelight phase modulation)in the PTS system is directly related to the pump power density.As a result,the PTS system can achieve higher sensitivity on a much shorter sensing path,thus significantly reducing the equipment volume and costs.Hollow-core fiber(HCF),has been widely applied in PTS systems to realize ultra-sensitive sensing,benefiting from its capability to guide high power density.However,the sensing chamber formed by the elongated air core within the HCF needs to be uniformly filled with the target gas which hinders the real-time detection.The solution of drilling micro holes on the HCF surface using a femtosecond laser has emerged.With the assistance of a miniaturized high-pressure gas pump,this approach reduces the time required for filling the gas into the HCF and achieves a response time in dozens of seconds.Performing micron-level local drilling on the HCF

关 键 词：光谱学 光热光谱 微纳光纤 外差干涉 光纤传感器 NH3检测 

分 类 号：TN25[电子电信—物理电子学]