狭缝光波导光耦合增强研究

发布时间：2018-02-06 00:58

本文关键词： 狭缝波导表面等离激元电场增强效应模式耦合　出处：《北京化工大学》2015年硕士论文　论文类型：学位论文

【摘要】：现代光学器件正朝着集成化,高速化,节能化方向发展。狭缝波导作为一种具有高局域性,高强度的光子器件,受到科学家们的广泛关注和研究,在传感器、光学机械设备驱动和纳米光子器件等领域具有重要潜在应用。本文首先分析表面等离激元的基本理论,讨论了时域有限差分法和光波段的金属色散模型,在此基础上研究狭缝波导和V型沟槽波导的光传输特性,提出了一种有效提升光波导中光限域的方法,揭示了光栅对光耦合增强的作用本质。提高介质狭缝波导的光耦合作用通常采用增大纳米线的介电常数或者减小狭缝区域内的介电常数的方法,这种传统方法虽然可以增强狭缝区域内的电场,但是狭缝中的磁场并没有得到相应增强。本文在两根硅纳米线的狭缝两边覆上了一层周期性银膜,不仅可以显著提高狭缝内的电场强度,而且磁场也得到了有效的增强,从而狭缝内的光能流提高了3倍。这种平行的金属光栅结构横向放置时,光场的增强随着狭缝宽度的增大而逐渐减弱,随着光栅间隙宽度的增大,狭缝内电场先增加后减小,当光栅间隙宽度约为入射光波长的0.01倍时,电场增强最大。通过电磁场理论分析,发现当光栅间隙宽度约为0.01波长时,平行光栅的等效介电常数最小,导致光场耦合作用最强。平行金属光栅纵向放置时,其光场增强作用表现出了不同的规律,随光栅间隙宽度增大,狭缝内电场增强逐渐减弱,当间隙约为5nm时增强作用开始失效。光场耦合最强时对应的光栅等效介电常数最小。在平行狭缝波导结构的基础上,研究了V型沟槽波导的光传输特性,发现金属光栅结构对沟槽内的电场和磁场均有显著增强,与平行狭缝波导光场增强规律一致。这种平行金属光栅在入射光波的作用下产生表面等离激元,使狭缝区域内的有效折射率降低,可以极大地增强光波导的光耦合作用。这种光耦合作用不仅可以适用于方形和V型光波导也可以应用在其他光波导中,在高限域光波导的设计中具有潜在应用。
[Abstract]:Modern optical devices are developing towards integration, high speed and energy saving. Slit waveguide, as a kind of photonic device with high localization and high intensity, has been widely concerned and studied by scientists in the sensor. Optical mechanical device driving and nano-photonic devices have important potential applications. In this paper, the basic theory of surface isopotons is analyzed, and the finite difference time-domain (FDTD) method and the metal dispersion model in optical wave band are discussed. On this basis, the optical propagation characteristics of slit waveguide and V-groove waveguide are studied, and an effective method to raise the optical limiting field in optical waveguide is proposed. The effect of grating on the enhancement of optical coupling is revealed. The method of increasing the dielectric constant of nanowires or decreasing the dielectric constant in slit region is usually used to improve the optical coupling of dielectric slit waveguides. Although this traditional method can enhance the electric field in the slit region, the magnetic field in the slit has not been enhanced accordingly. In this paper, a periodic silver film is coated on both sides of the slit of two silicon nanowires. Not only the electric field intensity in the slit can be significantly increased, but also the magnetic field can be effectively enhanced, thus the light energy flow in the slit can be increased by three times. The enhancement of light field decreases gradually with the increase of slit width. With the increase of grating gap width, the electric field in the slit increases first and then decreases, when the grating gap width is about 0.01 times of the incident wavelength. Through the theoretical analysis of electromagnetic field, it is found that when the gap width of grating is about 0.01 wavelength, the equivalent dielectric constant of parallel grating is minimum. When the parallel metal grating is placed longitudinally, the enhancement of the light field shows different laws. With the increase of the grating gap width, the electric field increases gradually in the slit. When the gap is about 5 nm, the enhancement begins to fail, and the equivalent dielectric constant of the grating is minimum when the light field coupling is strongest. Based on the parallel slit waveguide structure, the optical propagation characteristics of the V-shaped grooved waveguide are studied. It is found that the structure of metal grating increases the electric field and magnetic field in the grooves, which is consistent with the law of the enhancement of the optical field in the parallel slit waveguide. This kind of parallel metal grating produces surface isoexcitators under the action of the incident light wave. By reducing the effective refractive index in the slit region, the optical coupling of optical waveguides can be greatly enhanced, which can be used not only in square and V-shaped optical waveguides, but also in other optical waveguides. It has potential application in the design of high limit optical waveguide.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN252

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