硅基微环谐振器的设计制作及非线性应用

发布时间：2018-07-22 11:42

【摘要】：21世纪是一个高度信息化的时代,信息的传输、处理和存储面临越来越高的要求,传统的电互连技术正面临信号延迟、功耗和散热等“电子瓶颈”,取而代之的,光互连技术因不存在RC延迟、传输速率快、抗电磁串扰、传输带宽大、传输能耗低等优点被广泛应用于信息处理领域。绝缘体上硅材料(Silicon-on-insulator,简称SOI)由于其在通信波段透明、折射率差大以及与标准的CMOS (Complementary-Metal-Oxide-Semiconductor)工艺完全兼容等优点成为最热门的低成本高集成度光互连平台。在众多硅基光子集成器件中,微环谐振器由于对特定的波长谐振增强、光传输的方向和路径可控、结构紧凑、设计自由度大、便于与其它器件集成等优点,成为光子集成回路中最重要的基础功能单元之被用来构建多种不同用途的集成光学器件。由于微环谐振器对光强有较大的谐振增强作用,微环内的光功率密度比直波导内的大很多倍,其中的非线性效应将更加显著。本论文全面、深入地研究了硅基微环谐振器的工作原理和性质,详细阐述了微环谐振器的设计方法,探索了制作微环谐振器的重要工艺过程,并对微环谐振器中的光学非线性现象和光频梳应用展开了理论与实验研究。本文的研究成果可以总结为以下几个方面：(1)探索开发了基于不同材料体系(硅、二氧化硅、氮化硅等)的精密微纳加工工艺,主要包括材料沉积、电子束曝光、紫外光刻、等离子体感应耦合(ICP)干法刻蚀、湿法刻蚀、蒸镀剥离等。详细探索并优化了多种胶在多种衬底上的电子束曝光工艺；开发了不同材料体系上的Bosch分步深刻蚀、同步浅刻蚀、各向同性刻蚀的硅基ICP干法刻蚀和湿法腐蚀工艺,制备了高质量的波导、光栅、光子晶体、微环等。(2)设计并制备了单次刻蚀的垂直光栅耦合SOI微环谐振器,双端光栅耦合效率最高可达-8 dB,即40%,3 dB带宽约为35 nm,半径为40μm时,其Q值约为55329,消光比ER为18 dB,制备的SOI微环谐振器已达到国际先进水平,其双稳态和四波混频等非线性效应明显,为低功耗集成非线性器件奠定了基础。另外,通过在微环中引入MZI结构,利用热电级调制MZI双臂,在功耗9.82 mW时,首次实现了微环谐振器的谐振间隔从零到一整个FSR (1.17nm)的连续可调。(3)首次设计并制备了应用于厚Si3N4薄膜上的聚焦型高耦合效率宽谱光栅耦合器,该耦合器结合倒锥和聚焦型光栅齿,结构紧凑,制作简单,耦合效率高,对准容差大,便于器件的大面积制备与测试。耦合器的尺寸为70.2 μm×19.7μm,最佳耦合效率-3.7 dB,1-dB带宽54 nm。(4)提出了SU-8覆盖的刻蚀型端面耦合方案。使用相向的锥形结构,结合聚合物曝光与端面刻蚀的方法,通过电子束曝光获得聚合物与光纤的耦合端面,提高端面质量,减小耦合损耗。模拟得到的光场从氮化硅波导到SU-8波导中的模式耦合损耗共为0.24 dB。(5)深入研究基于片上微环谐振器的光学频率梳产生原理,设计并制作了C波段内宽带零色散平坦、耦合效率可控的Si3N4上微环谐振器,利用LPCVD、电子束曝光、剥离蒸镀和ICP干法刻蚀等工艺,制备了不同半径、不同耦合间距的氮化硅微环谐振器,尝试利用环对光强的谐振放大以及Si3N4的三阶非线性效应产生级联四波混频进而激发光频梳。
[Abstract]:Twenty-first Century is a highly informative age, information transmission, processing and storage are facing more and more high requirements. The traditional electrical interconnection technology is facing the "electronic bottleneck" such as signal delay, power consumption and heat dissipation. The optical interconnection technology has no RC delay, fast transmission rate, anti electromagnetic crosstalk, large transmission bandwidth and low transmission energy consumption. Such advantages are widely used in the field of information processing. Silicon-on-insulator (SOI) has become the hottest low cost and high integration optical interconnection platform because of its advantages of transparent communication band, poor refractive index and fully compatible with standard CMOS (Complementary-Metal-Oxide-Semiconductor) technology. In polysilicon based photonic integrated devices, microring resonators have become the most important basic functional units in photonic integrated circuits, due to the enhancement of specific wavelength resonance, the direction and path of light transmission, the compact structure, the large design freedom and easy integration with other devices. Because of the greater resonance enhancement of the light intensity by the microring resonator, the optical power density in the micro ring is much larger than that in the direct waveguide, and the nonlinear effect will be more significant. This paper has thoroughly studied the working principle and properties of the silicon based microring resonator, and elaborated the design method of the microring resonator. The important process of microring resonator is made, and the optical nonlinear phenomena and optical frequency comb applications in the microring resonator are studied theoretically and experimentally. The research results of this paper can be summarized as follows: (1) the precision micro processing technology based on different material systems (silicon, silicon dioxide, silicon nitride, etc.) is explored and developed. Mainly including material deposition, electron beam exposure, UV photolithography, plasma induced coupling (ICP) dry etching, wet etching, evaporation stripping, and so on. The electron beam exposure technology of various kinds of adhesives on various substrates is explored and optimized, and the Bosch step deep etching, synchronous shallow etching, and isotropic etching of silicon on different material systems are developed. High quality waveguide, grating, photonic crystal, micro ring, etc. are prepared by ICP dry etching and wet etching. (2) a single etching vertical grating coupled SOI microring resonator is designed and fabricated. The maximum coupling efficiency of double end grating can reach -8 dB, that is, 40%, 3 dB bandwidth is about 35 nm and the radius is 40 micron m, and the extinction ratio ER is 18 dB, The SOI micro ring resonator has reached the international advanced level. Its bistability and four wave mixing have obvious nonlinear effects. It lays the foundation for low power integrated nonlinear devices. In addition, by introducing MZI structure in the micro ring, using the thermoelectric level modulation MZI double arm and the power consumption of 9.82 mW, the resonant interval of the micro ring resonator is first realized from zero. Continuous adjustable FSR (1.17nm). (3) the focus type high coupling efficiency wide spectrum grating coupler applied to thick Si3N4 thin film is first designed and fabricated. The coupler is combined with inverted cone and focused grating teeth. It has compact structure, simple fabrication, high coupling efficiency, large alignment tolerance and convenient for large area preparation and testing of devices. Couplers The size is 70.2 mu m x 19.7 mu m, the best coupling efficiency -3.7 dB and 1-dB bandwidth 54 nm. (4) have proposed a SU-8 covered etching end coupling scheme. Using the conical conical structure, combined with the method of polymer exposure and end etching, the coupling end of the polymer and fiber is obtained through the electron beam exposure, and the end surface quality is improved and the coupling loss is reduced. The mode coupling loss of the simulated optical field from silicon nitride waveguide to SU-8 waveguide is 0.24 dB. (5). The principle of optical frequency comb generation based on the microring resonator is studied. The C band zero dispersion flat, coupled efficiency controlled Si3N4 microring resonator is designed and fabricated, and LPCVD, electron beam exposure, stripping evaporation and I are used. The silicon nitride microring resonator with different radius and different coupling spacing is prepared by CP dry etching. The resonant amplification of the light intensity and the cascade four wave mixing of the three order nonlinear effect of Si3N4 are used to generate the frequency comb.
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN629.1

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