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本文研究了一种非对称银膜多孔硅-氟化钙混合等离子体波导, 并对其模式特性和波导灵敏度进行了分析. 利用有限元方法分析了波导中两个不同偏振态基模(PM 1和PM 2)的有效折射率、传输损耗、归一化有效模场面积、品质因数和波导灵敏度, 并对几何参数进行优化. 结果表明, 在中红外波长3.5 μm附近, 非对称银膜多孔硅-氟化钙混合等离子体波导具有良好的模场约束能力和低损耗特性; 此时, PM 1和PM 2的归一化有效模场面积分别为0.30和0.52, 传输损耗分别为0.019 dB/μm和0.016 dB/μm, 品质因数分别为1335.54和1594.99, 波导灵敏度分别为0.080和0.064. 通过制造容差分析可知, 非对称银膜多孔硅-氟化钙混合等离子波导在 ± 10 nm的制造容差范围内保持了良好的模式特性和传感特性. 非对称银膜多孔硅-氟化钙混合等离子体波导结构简单, 损耗小, 易于实现表面等离子体传感, 为无标记生物化学传感提供了一种可行的方案, 另外, 波导的非对称结构也可用于模式偏振态变换.In this paper, a porous silicon-calcium fluoride hybrid plasmonic waveguide (PS-CaF2 HPW) with an asymmetric silver film is studied. The PS-CaF2 HPW is composed of a PS strip waveguide deposited with asymmetric CaF2 and Ag thin film layers on an SiO2 substrate. In the mid-infrared (MIR) region, the mode characteristics and waveguide sensitivity of the mode in the PS-CaF2 HPW are simulated by using the finite element method (FEM). The results show that there are two fundamental modes (PM 1 and PM 2) with different polarization states in the PS-CaF2 HPW. The real part of the effective refractive index (Re(neff
)), transmission loss (α), normalized effective mode field area (A), quality factor (FOM) and sensitivity (Swg) for each of the PM 1 and the PM 2 are studied and optimized. Moreover, the effect of temperature on the performances of the PS-CaF2 HPW is also analyzed. Firstly, the mode field distributions calculated by the FEM indicate that the mode field energy for each of the PM 1 and PM 2 in the PS-CaF2 HPW is mostly restricted to the PS layer and CaF2 layer. Comparing with conventional dielectric waveguides, the mode field energy of the PS-CaF2 HPW is well confined in the PS layer and CaF2 layer. The geometric parameters of the PS-CaF2 HPW are optimized by changing the geometric parameters (W1, W2, and W3). When W1 = 1500 nm, W2 = 300 nm, W3 = 70 nm, and the operating wavelength is ~3.5 μm, α and FOM are 0.019 dB/μm and 1594.99 for the PM 1, and α and FOM are 0.016 dB/μm and 1335.54 for the PM 2, respectively. Secondly, the waveguide sensitivity of the PS-CaF2 HPW is analyzed. The results show that the size of PS layer has a great influence on the waveguide sensitivity. The waveguide sensitivity decreases with the size of the PS layer increasing. In addition, the PS-CaF2 HPW has good temperature resistance. Moreover, temperature has almost no effect on Re(neff ), nor α nor A nor FOM nor Swg in a temperature range from -40 K to 40 K. Finally, the fabrication tolerances of the PS-CaF2 HPW are demonstrated, and the good properties are maintained in a size tolerance range from -10 nm to 10 nm. With the advantages in propagation property and loss reduction, the PS-CaF2 HPW provides a feasible label-free biochemical sensing scheme and a method of polarization control devices. -
Keywords:
- hybrid plasmonic waveguide /
- surface plasmon polaritons /
- propagation property /
- waveguide sensitivity
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中国物理学会期刊
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