基于表面等离子体狭缝波导的三次谐波研究

发布时间：2018-03-17 12:25

本文选题：表面等离子体狭缝波导　切入点：三次谐波　出处：《哈尔滨工业大学》2014年硕士论文　论文类型：学位论文

【摘要】：近年来,中红外波段光学凭借其在光通信和生物医学传感等领域的广泛应用激发了越来越多的研究兴趣。三次谐波在中外红领域的应用主要包括带内光信噪比探测,微米级器件几何结构成像,三维数据存储和生物材料研究等。基于此,研究基于中红外的高效三次谐波转换器件是很有必要和有意义。本文对中红外及三次谐波的基本原理和应用进行了简要回顾。通过对三次谐波的基本原理以及耦合模差分方程的推导和分析引出在波导器件中产生高效三次谐波的三个关键因素。一方面利用具有高三阶非线性极化率的非线性介质材料作为三次谐波产生的主要媒介;另一方面通过合理设计波导结构参数实现泵浦波和三次谐波相位匹配;最后一方面设计特殊波导结构调整高阶模的电场分布实现大的泵浦-三次谐波模式重叠积分系数。经过调研,表面等离子体狭缝波导结构对光的限制和加强特性可以很好的同时满足上述三方面要求。表面等离子体纳米结构除了能够增强非线性效应,还能使非线性光学组件缩减至微米级别,有利于光器件芯片集成。用此类波导结构辐射三次谐波,波导的非线性参数能通过调节波导的结构参数合理控制。基于表面等离子体狭缝波导结构特性和三次谐波工作原理,本文设计几种特殊波导结构实现高效三次谐波(中红外到近红外)转换。首先本论文提出了两种非对称表面等离子体狭缝波导结构。狭缝上层引入硅的主要目的包括两方面。一方面,阻止上层金属覆盖层对DDMEBT聚合物中电场的影响,使得相位匹配能够通过调节波导结构参数实现;另一方面,破坏高阶模电场分布的对称性,限制高阶模电场的负电场分量分布在硅狭缝中,提高对应的泵浦-三次谐波重叠积分系数。接着本论文利用混合狭缝波导结构导模的特殊性实现了更高效率三次谐波产生。由于高阶模负电场分量全部限制在硅平板中,三次谐波效率得到大大提高。基于非对称表面等离子体狭缝波导和混合狭缝波导的研究,本论文提出了双狭缝金属波导结构,实现了较高三次谐波转换效率,为未来设计金属纤芯光纤提供理论指导。最后,本论文详细研究了双光子吸收效应对三次谐波转换效率的影响并提出解决方案。
[Abstract]:In recent years, due to its wide applications in optical communication and biomedical sensing, the mid-infrared band optics has aroused more and more research interests. The application of third-harmonic in the red field mainly includes in-band optical signal-to-noise ratio (SNR) detection. Micron device geometry imaging, 3D data storage, biomaterial research, etc. It is necessary and meaningful to study the high efficiency third harmonic converter based on middle infrared. The basic principle and application of middle infrared and third harmonic are briefly reviewed in this paper. The basic principle and coupling of third harmonic are briefly reviewed. The derivation and analysis of the combined mode difference equation lead to three key factors for the generation of high efficiency third harmonic in waveguide devices. On the one hand, the nonlinear dielectric material with high third order nonlinear polarizability is used as the main medium for the generation of third harmonic. On the other hand, the phase matching of pump wave and third harmonic is realized by reasonably designing waveguide structure parameters. Finally, a special waveguide structure is designed to adjust the electric field distribution of high order modes to achieve a large pump third harmonic mode overlap integral coefficient. The limiting and strengthening properties of the surface plasma slit waveguide structure can satisfy the above three requirements well. The surface plasma nanostructures can enhance the nonlinear effect. It can also reduce the nonlinear optical components to micron level, which is beneficial to the chip integration of optical devices. The nonlinear parameters of the waveguide can be reasonably controlled by adjusting the structural parameters of the waveguide. In this paper, several special waveguide structures are designed to achieve high efficiency third-harmonic (mid-infrared to near-infrared) conversion. Firstly, two kinds of asymmetric surface plasma slit waveguide structures are proposed. The main purpose of introducing silicon into the upper slit is silicon. There are two aspects. On the one hand, In order to prevent the influence of the upper metal coating on the electric field in the DDMEBT polymer, phase matching can be achieved by adjusting the waveguide structure parameters, on the other hand, the symmetry of the electric field distribution of the higher-order modes is destroyed. The distribution of the negative electric field components of the high-order mode electric field in the silicon slit is limited. The corresponding pump third harmonic overlapping integral coefficient is improved. Then, by using the particularity of the guide mode of the mixed slit waveguide structure, a higher efficiency third harmonic generation is realized. Because the high order mode negative electric field components are all confined to the silicon plate, the high order mode negative electric field component is limited to the silicon plate. The third harmonic efficiency has been greatly improved. Based on the research of asymmetric surface plasma slit waveguide and hybrid slit waveguide, this paper presents a dual-slit metal waveguide structure, which achieves a higher third harmonic conversion efficiency. It provides theoretical guidance for the design of metal-core fiber in the future. Finally, the effect of two-photon absorption effect on the third-harmonic conversion efficiency is studied in detail and a solution is proposed.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN814

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