本文提出并研究了一种基于干涉增强型混合光波导（IE-HOW）的高灵敏折射率传感器。IE-HOW包括微纳U型光波导与微瓶腔，通过光纤熔融拉锥以及电弧放电方法制备并级联而成。基于强倏逝场效应，实现了对折射率的高灵敏传感测试。实验结果表明，当微纳U型光纤锥区直径为4.88 μm时，IE-HOW的折射率灵敏度相比于普通单个无干涉增强微纳U型光波导提高了3倍，高达8813.26 nm/RIU（灵敏度单位），线性度R²>0.9。该传感器具有灵敏度高、损耗低、结构紧凑、稳定性好等优点，在环境监测、生化检测、临床诊断等领域有着广阔的应用前景。

提出一种基于锥形七芯光纤的紧凑型光纤超声传感器，并进行了实验验证。该传感器由熔接在两根单模光纤之间的锥形七芯光纤制成，形成单模光纤—锥形七芯光纤—单模光纤的级联结构。由于单模光纤和七芯光纤的纤芯不匹配，容易激发高阶模式，被激发的多种模式的光波继续沿着七芯光纤传播，然后到达锥形区域。由于锥度直径的急剧减小，模式间发生干涉，传感器的灵敏度得到提高。制备了不同直径的锥形七芯光纤，并对其模间干涉和超声测量进行了对比分析。超声波在水中传播时，将周期性地改变周围液体的折射率，基于锥形光纤的倏逝场效应，调制锥形光纤中光波的传输。该超声波传感器具有制作简单、信噪比高、频率响应宽等特点。

We propose a polarization-insensitive design of a hybrid plasmonic waveguide (HPWG) optimized at the 3.392 μm wavelength which corresponds to the absorption line of methane gas. The waveguide design is capable of providing high mode sensitivity (Smode) and evanescent field ratio (EFR) for both transverse electric (TE) and transverse magnetic (TM) hybrid modes. The modal analysis of the waveguide is performed via 2-dimension (2D) and 3-dimension (3D) finite element methods (FEMs). At optimized waveguide parameters, Smode and EFR of 0.94 and 0.704, can be obtained for the TE hybrid mode, respectively, whereas the TM hybrid mode can offer Smode and EFR of 0.86 and 0.67, respectively. The TE and TM hybrid modes power dissipation of ~3 dB can be obtained for a 20-μm-long hybrid plasmonic waveguide at the 60% gas concentration. We believe that the highly sensitive waveguide scheme proposed in this work overcomes the limitation of the polarization controlled light and can be utilized in gas sensing applications.

利用有限元法研究了弱耦合偏芯少模光纤高阶模式的模场特性、隐失场特性及弯曲损耗。分析了光纤参数对相邻模式之间最小有效折射率差的影响,并对偏芯光纤进行优化,使其支持10个线偏振模式且满足弱耦合条件;此外,研究了波长为1550 nm条件下,10个线偏振模式的功率分布和弯曲损耗。研究结果表明,在整个C波段,相邻模式之间最小有效折射率差均大于10 -4;且该光纤在高阶模态下表现出更强的隐失场强度、更高的传感灵敏度和更大的弯曲损耗,同时可以区分特定的弯曲方向。这些研究结果对于提高传感器灵敏度有潜在的应用价值。

Zero-mode waveguides have become important tools for the detection of single molecules. There are still, however, serious challenges because large molecules need to be packed into nano-holes. To circumvent this problem, we investigate and numerically simulate a novel planar sub-wavelength 3-dimension (3D) structure, which is named as near-field spot. It enables the detection of a single molecule in highly concentrated solutions. The near-field spot can produce evanescent waves at the dielectric/water interface, which exponentially decay as they travel away from the dielectric/water interface. These evanescent waves are keys for the detection of fluorescently tagged single molecules. A numerical simulation of the proposed device shows that the performance is comparable with a zero-mode waveguide. Additional degrees-of-freedom, however, can potentially supersede its performance.

为了减小光纤包层厚度并提升干涉仪的折射率灵敏度,设计一种结构简单、容易制作的光子晶体光纤马赫-曾德尔干涉仪。首先,在两根单模光纤之间熔接一段光子晶体光纤(PCF);然后,在自制的腐蚀槽中采用氢氟酸进行化学腐蚀来减小包层厚度,并通过控制变量的方法,研究光子晶体光纤的长度、腐蚀时间,以及环境温度对制得的干涉仪灵敏度的影响。结果表明,随着光纤长度增加,制得的干涉仪的灵敏度提高。将3 cm的PCF在质量分数为40%的氢氟酸溶液中腐蚀40 min后,制得的干涉仪的灵敏度增加了约3倍。环境温度对制得的干涉仪的灵敏度几乎无影响。

In this work, we have evaluated the biosensing capability of the porous silicon (PSi) based sidewall Bragg-grating resonator. The approximation of the quasi-TE mode full vector for the eigenmode calculation is performed using a full vector mode solver. The transmission spectra of the device are evaluated using the transfer matrix method. We have observed a shift in the resonant band for a change in the refractive index of biomaterial in the upper cladding region. The theoretical value of the bulk sensitivity is calculated to be 387.48 nm/RIU. The device is suitable for biosensing application due to its ability of interacting signal with the infiltrated analytes in the PSi waveguide core.

当空心微结构光纤纤芯的尺寸和波长相近时, 光在纤芯中的传输大大增强, 并会在纤芯周围产生很强的倏逝场。报道了一种新型的纤芯直径仅为2 μm的空气悬浮芯微结构光纤, 该光纤通过薄片堆积法拉制而成, 具有大倏逝场和微米级孔径的单元结构, 在532 nm波长处的损耗为0.16 dB/cm, 非常适合用于生化物质的传感探测。以该光纤作为传感探针, 结合激光技术搭建了一套简易的荧光光谱探测系统, 使用此系统对纳升量级的生物荧光标记材料CdTe/CdS/ZnS量子点进行荧光探测分析。利用该系统可探测荧光量子点的极限约为1 nmol/L, 相当于3.78×107个量子点, 实现了高灵敏度、快速探测。基于空气悬浮芯微结构光纤的荧光检测系统为量子点标记的生物材料的灵敏检测提供了新的方法和思路。