【作者】 吴华明；

【导师】 周治平；

【作者基本信息】 华中科技大学 ， 光电信息工程， 2010， 博士

【摘要】 光栅作为一个历久而弥新的光学器件,随着现代微纳技术及集成光路的发展,特别是硅基光电子学的发展,它也在不断的发展和完善中,同其他光电器件一起,光栅为人类的社会和经济发展做出了不可磨灭的贡献。与均匀光栅相比,非均匀光栅增加了设计自由度,能灵活控制光栅区域进行傅立叶级数展开时各个分量的分布,且能阻止光栅中泄漏模的快速衰减,实现宽带、高效反射等功能。此外,非均匀光栅还能实现宽谱的角度响应,这能降低微光学系统对准难度。鉴于硅基微纳光学器件是实现光路集成、片上光电转换以及探测的重要基础元件,论文所有研究将聚焦于微纳尺度范围内。本文在“国家重点研究发展计划(973计划)前期预研专项”和“国家自然科学基金”的支持下,重点研究硅基微纳二元非均匀光栅的器件及应用,取得了如下成果：(1)从严格耦合波分析(rigorous coupled-wave analysis, RCWA)方法出发,结合本论文实际情况,推导出了基于绝缘体上硅(silicon-on-insulator, SOI)材料系统的多层非均匀光栅结构的严格耦合波分析法,此方法表现出了较好的数值稳定性。(2)根据严格耦合波分析方法并结合时域有限差分算法,采用单层非均匀光栅结构,设计了一种结构紧凑、高性能的偏振分束器。源于构成材料的高折射率差以及非均匀光栅层的形状调制,在90nm(1.53～1.62μm)的光谱范围内,该结构表现出较高的衍射效率和消光比,并在中心波长1.57μm处,获得了相对较大的角度带宽。(3)由严格耦合波分析方法结合粒子群优化算法(particle swarm optimization, PSO),设计和优化了一种高性能的非均匀光栅反射镜。得益于横电场(transverse electric, TE)偏振光谐振模的共存及相互作用,该器件在630m宽谱范围内(1.47～2.1μm),具有反射率高,在中心波长1.8μm处,角度带宽大的优越性能。作为应用实例,本论文还设计了一种用于氮化镓基短波长发光二极管芯片的非均匀光栅反射镜,以提高芯片的外量子效率。(4)应用多层光栅严格耦合波分析方法及粒子群优化算法,还设计、优化并展示了一种基于多层非均匀光栅结构的高性能偏振无关反射镜。源于横电场(TE)和横磁场(transverse magnetic, TM)偏振光泄漏模谐振的同时共存及相互作用,该结构在宽谱范围内,表现出很高的反射效率,较低的插入损耗(insertion loss, IL)和偏振相关损耗(polarization-dependent loss, PDL),并在中心波长1.68μm处,获得了较大的角度带宽。此外,数值分析表明,该器件还表现出较好的工艺容差性。更多还原

【Abstract】 With the rapid development of integrated optics and silicon photonics, the grating has attracted increasing interest because some novel merits arise when the device dimension goes down to subwavelength. Combined with other optical elements, the grating related devices have made great contributions to human society and economic development. Compared with uniform gratings, the nonuniform gratings have the advantages of increasing design freedom, controlling over the Fourier series component distribution of the structures and removing the leaky modes degeneracy. They can offer the combined merits of high reflectivity over a broadband spectrum and good angular bandwidth, which makes the alignment problems encountered in implementing compact micro-optic systems quite moderate. Since silicon based micro/nano photonic devices have the advantage of a compact structure with the potential for monolithic integration with optical-to-electrical on-chip conversion and detection, all thesis work are confined in the micro/nano domain. Supported by the "National Basic Research Program of China" and "National Natural Science Foundation of China", the design and applications of the nonuniform gratings are systematically studied in this thesis, and a number of achievements are obtained as following:(1)In this thesis, a numerically stable and systematic implementation of the rigorous coupled-wave analysis (RCWA) for the general silicon-on-insulator (SOI) multilayered grating structures is presented for both transverse electric (TE) and transverse magnetic (TM) polarizations.(2)A broadband compact polarizing beam splitter (PBS) constructed by only a single layer subwavelength nonuniform profile grating is proposed and demonstrated. The properties of the grating PBS are investigated by rigorous coupled-wave analysis. It is shown that, over a broadband spectrum of 1.53～1.62μm, the grating PBS demonstrates high diffraction efficiencies with extinction ratio (ER) greater than 16dB and a comparatively wide angular bandwidth. Effects of deviation from the design parameters on the performance of the grating PBS are also presented.(3)A wideband reflector realized by only a single layer subwavelength grating is addressed. Resulting from the co-existence and interaction of TE leaky modes, over a broadband spectrum of 1.47～2.1μm, the reflector demonstrates high reflectivity and wide angular bandwidth at 1.8μm. Enhancement of light extraction in a GaN-based LED employing a nonuniform grating reflector is also proposed. The result of high angle-averaged reflectivity up to 93.5% from 300nm to 450nm predicts the potential enhancement of light-extraction efficiency of GaN LEDs with the grating reflectors.(4)A polarization insensitive reflector constructed by a multilayered grating structure with nonuniform profile is proposed. Rigorous coupled-wave analysis (RCWA) for multilayered grating structure is adopted to theoretically investigate the properties of the structure. It is shown that in both TE) and TM polarized waves, over a broadband spectrum, the reflector demonstrates very high reflectivity, low insertion loss and polarization-dependent loss and a good angular insensitivity at 1.68μm. A reasonably good tolerance of fabrication error is also presented by numerical analysis of device performance degeneration resulting from parameter deviations.更多还原