Kumar Shambhu, Maurya Jitendra Bahadur, Roumi Bita, Abdi-Ghaleh Reza, Prajapati Yogendra Kumar
Appl Opt. 2023 Jun 1;62(16):E130-E136. doi: 10.1364/AO.481145.
In this paper, a D-shaped optical fiber plasmonic sensor using planar and grating structures of silver and gold metals is simulated using the finite element method under the wave optics module of COMSOL Multiphysics. Performance defining parameters are based on (i) the transmittance curve, viz., resonance wavelength ( ), shift in resonance wavelength ( ), minimum transmittance ( ), and bandwidth (BW), and (ii) on electric field distribution of a surface plasmon wave, viz., penetration depth (PD) and propagation length (PL) obtained for the considered sensor structures. It is found that gold gives wider BW than silver (e.g., at 1.39 refractive index of the sample: 480% for the planar case and 241% for the grating case), which deteriorates sensor performance by degrading detection accuracy. However, gold gives higher than silver (at 1.40-1.39=0.01 change in refractive index of the sample: 18.33% for the planar case and 16.39% for the grating case), which improves sensor performance and enhances sensitivity. A grating slightly increases the BW and for both gold and silver. Further, with respect to silver, the sensor that contains gold demonstrates higher PD (e.g., 22.32% at 1.39 refractive index of the sample for the planar case) and lower PL (e.g., 22.74% at 1.39 refractive index of sample for the planar case). A grating increases the PD (e.g., 10% for silver at 1.39 refractive index of the sample), whereas it decreases the PL (e.g., 8.73% for silver at 1.39 refractive index of the sample). Lower PL signifies the localization of the field, whereas higher PD enables the sensor to detect larger molecules. Therefore, the sensor with grating metals provides better sensitivity with reduced detection accuracy for the detection of comparatively larger molecules.
在本文中，使用COMSOL Multiphysics波动光学模块下的有限元方法，对一种采用银和金金属的平面及光栅结构的D形光纤等离子体传感器进行了模拟。性能定义参数基于：(i) 透射率曲线，即共振波长（ ）、共振波长的偏移（ ）、最小透射率（ ）和带宽（BW）；以及 (ii) 表面等离子体波的电场分布，即所考虑的传感器结构的穿透深度（PD）和传播长度（PL）。研究发现，金的带宽比银宽（例如，在样品折射率为1.39时：平面情况为480%，光栅情况为241%），这会因降低检测精度而使传感器性能变差。然而，金的 比银高（在样品折射率变化1.40 - 1.39 = 0.01时：平面情况为18.33%，光栅情况为16.39%），这会改善传感器性能并提高灵敏度。对于金和银，光栅都会略微增加带宽和 。此外，相对于银，含有金的传感器具有更高的穿透深度（例如，在样品折射率为1.39时，平面情况为22.32%）和更低的传播长度（例如，在样品折射率为1.39时，平面情况为22.74%）。光栅会增加穿透深度（例如，在样品折射率为1.39时，银的穿透深度增加10%），而会降低传播长度（例如，在样品折射率为1.39时，银的传播长度降低8.73%）。较低的传播长度意味着场的局域化，而较高的穿透深度使传感器能够检测更大的分子。因此，带有光栅金属的传感器在检测相对较大分子时，灵敏度更高，但检测精度会降低。
