新型光子晶體光纖傳感器的基礎研究

陸穎　姚建銓　畢衛紅　齊躍峰

摘 要：光子晶體光纖因其獨特的光學特性、結構可靈活設計的優點以及對空氣孔中填充的材料參量變化敏感的特點而成為近幾年來傳感領域的研究熱點。該課題對填充金屬納米材料、氣體、液體等材料的光子晶體光纖的光譜特性、溫度傳感特性及光子晶體光纖光柵的成柵機理進行了深入的研究，得到了一些很有價值的結論，為基于PCF的傳感器的實現與應用及進一步拓寬光纖的原有領域奠定了良好的基礎。（1）設計了一種有源PCF-SPR傳感器，其特點是將有源內腔檢測技術與表面等離子共振相結合，利用一根包層氣孔充入金屬納米線溶液纖芯摻雜激活介質的光子晶體光纖實現探測激光產生、信息傳感及光信號傳輸集一體的有源傳感，并且由于纖芯的折射率可達到1.58，從而也拓寬了PCF-SPR傳感器的探測范圍。（2）針對在PCF氣孔鍍金屬納米膜的工藝較難的情況，實驗上采用填充Ag納米線懸浮液的方法實現了PCF-SPR溫度傳感， 實驗結果與仿真結果變化趨勢一致，此方案可保持PCF用于表面等離子共振傳感器的某些優點又簡化了工藝操作。（3）設計了一種聚合物光子晶體光纖用于表面等離子共振傳感器，這種光纖采用聚甲基丙烯酸甲酯制作，金屬膜只需鍍在光纖的外部，方便操作。仿真模擬結果表明，聚合物PCF半徑、中心空氣孔數量及空氣孔的直徑對波長靈敏度的影響很小，這樣降低了對PCF制作的精密度的要求，有利于PCF的實際制作。（4）研究了一種基于混合液體填充的反射式光子晶體光纖溫度傳感探頭，這種結構使得傳感部分可以方便的伸入待測環境，相對于透射式傳感裝置而言，該種反射裝置具有更為靈活實用的優點。實驗結果表明，該種光子晶體光纖溫度傳感器可以在特定溫度范圍內呈現線性響應，其溫度靈敏度約為1 dB/°C。此外，根據不同的溶液配比，該種傳感器呈現可調諧的溫度靈敏區間。（5）對由光子晶體光纖光柵組成的新型生物傳感器特性進行了研究，重點對光纖結構參數（空氣孔直徑和孔間距）、光柵參數（光柵周期和周期個數）、塌縮程度和塌縮方式對諧振波長的影響進行了分析，研究結果表明，隨著空氣孔直徑的增大、孔間距的減小、光柵周期的增大和塌縮程度的減小，其諧振波長向短波方向發生漂移，隨著周期個數的增大，其諧振波長未發生明顯漂移。

關鍵詞：光子晶體光纖 光子晶體光纖光柵 表面等離子體共振 光纖傳感 金屬納米材料

Abstract：Photonic crystal fiber （PCF） has become the research focus in the field of sensors with the unique advantages of that it can be designed flexibly and exhibits a high sensitivity for the change of the filled gas， liquid， and metal-based nanomaterials. This subject has analyzed the spectral and temperature sensing characteristics of PCF with different materials by changing the structure parameters and the factors related to the surrounding environment. The results show that PCF based sensors is promising for related applications.（1）A surface plasmon resonance （SPR） refractive index （RI） sensor based on ytterbium-doped PCF filled with metal nanowires and analyte is proposed. With the proposed sensor， the output power of the ytterbium-doped PCF laser can be influenced obviously by a bit change of the refraction index of analyte in the air holes to achieve the intra-cavity fiber sensing. This PCF sensing system has great practical value and significance for their advantages of compact structure and high sensitivity.（2）A SPR temperature sensor based on PCF with silver nanowires is designed and investigated experimentally. The results show that the temperature sensitivity is as high as 3.5 nm/℃ with the experiment， which can provide reference for the implementation and application of PCF-based SPR temperature sensor or other PCF-based SPR sensing.（3）An intra-cavity sensor based on a dual-wavelength Er-doped fiber laser is proposed and investigated experimentally. A measurement of the relative sensitivity enhancement of 158.5 is obtained.（4）A polymer PCF-SPR sensor is designed， in which a metal film can be deposited on the outer side of the fiber instead of coating in the holes of the conventional PCF. Numerical results show that excellent sensing characteristics of the structure can be achieved.（5）A kind of label-free refractive index biosensor based on long-period gratings （LPGs） inscribed in microstructured optical fibers （MOFs） is theoretically studied. Numerical results show that an ultrahigh refractive index sensitivity of approximately 397.3 nm/RIU over the refractive index range of 1.4～1.5 is achieved. Moreover， the sensitivity of the grapefruit MOF can be improved by reducing the periods of gratings. In addition， the shift of the resonant wavelength is linear to the analyte thickness with good sensitivity about 0.6 nm/nm. It is expected to play a great role in theoretical guidance for further development of biosensors.

Key Words：Photonic crystal fiber；Surface plasmon resonance；Fiber sensor；Metal-based nanomaterials

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