Details of Research Outputs

Author (Name in English or Pinyin)
ZHOU, Taojie
Author (Name in Chinese)周陶杰
Degree TypeDoctor of Philosophy
Supervisor(s) (Name in English or Pinyin)ZHANG, Zhaoyu
Date Issued2020
Degree GrantorThe Chinese University of Hong Kong
Place of ConferralShenzhen
Degree DisciplineComputer and Information Engineering

The recent exponential growth in data traffic requires a more efficient on-chip optical interconnection method with lower energy consumption, higher modulation speed and higher density of processing unit. Therefore, lasers, with small footprint, low power consumption and higher modulated speed is urgently demanded, which can be realized by microscale or nanoscale lasers. Semiconductor microlaser with microcavity configuration have raised considerable interest and are presently the most promising components of the photonics integrated circuits (PICs) as promising light sources, owing to their low power consumption, wafer-based processing, as well as enabling dense integration with other functions on a single chip. The present work explores the design, fabrication and characterization of semiconductor micro lasers, by using semiconductor quantum wells or quantum dots as gain materials. A background of this thesis is demonstrated in Chapter 1. The fabrication optimization produces and optical setup for semiconductor micro lasers are depicted in Chapter 2. The proposed designed novel micro cavity and lasers are demonstrated in Chapter 3. Then micro lasers on two platforms will be presented, one is flexible micro lasers aimed at exploring flexible PICs presented in Chapter 4 and Chapter 5. The other is micro lasers directly grown on silicon, which is preferred for low-cost and dense PICs discussed in Chapter 6. Then a brief conclusion of this work will be conducted in Chapter 6. Then a brief conclusion of this work will be conducted in Chapter 7, following by four appendixes. Microlasers including micro disk, mirroring, and photonics crystal lasers are presented by using etching method. The pattern of designed devices are defined by electron beam lithography, and is transferred in the semiconductor materials by using plasma dry etching. A detailed procedure and etching optimization for the device fabrication, as well as the optical setup for the characteristic is presented in Chapter 2. The characterization of the micro lasers is investigated through scanning electron microscopy, micro-photoluminescence (μ-PL), etc. The optimization of plasma dry etching is discussed in detail. Optimized recipes for GaAs-based micro disk cavity, PC micro cavity, as well as InP PC micro cavity will be demonstrated. Smooth etching surface and vertical profile of demonstrated semiconductor microcavity is achieved. In Chapter 3, fivefold PC microcavity with fivefold rotational symmetry is presented. Analogous to QPC structures, triangular and square PC microcativities, the existence of photonics band gap of a fivefold PC structure indicates the potential applications such as for ultraslow threshold lasers. In addition, two kinds of fivefold PC micro cavities with six defects air holes and one defect air hole have been proposed, respectively. The resonant defects modes such as WGMs, monopole mode and dipole mode are proven to be sustained by using three-dimensional finite-difference time-domain (3D-FDTD) method. The existence of defects mode with high Q-factor can further slow that the fivefold microcavity could present widely potential applications. In addition, cantilever-based freestanding mirroring lasers were demonstrated based on InGaP/InGaAIP quantum wells emitting in the red region. The rotational symmetry of the mirroring cavity is broken by introducing the connected cantilevers, which induce degenerated mode splitting and single mode losing emission. The connected cantilevers can not only provide mechanical support for freestanding mirroring lasers but also function as waveguides for efficient light extraction. The application of cantilever-based microring lasers had been studied for a refractive index sensor and flexible local strain gauges. Flexible integrated photonic elements can exhibit promising characteristics and enable novel applications in soft robotic as well as body-attachable, conformable devices. In Chapter 4, ultra-thin curved and flexible visible micro disk lasers with a single-mode Laing emission and a high Q-factor of ~17000 was achieved, which enable a 3D spatial photons compared with the conventional 2D in-place WGMs. The curved micro disk and multilevel photon sources for the photonics integrated circuits. In addition, flexible presented in Chapter 5, of which the spectra are sensitive to the flexible substrate deformation. The flexible micro lasers are also expected to function as tunable light sources for the PICs and microscale local strain gauges with low-power consumption. The integration of well-established III-V photonics devices on silicon is a promising solution to realize efficient Is-based light-emitting sources, due to the in-direct band gap property of bulk group-IV materials. This thesis explore the solutions of monolithically integrated high-performance micro lasers on silicon in Chapter 6. The subwavelength scale (~1.1μm) microdisk lasers directly grown on silicon will be depicted, operating at room temperature under continuous-wave optical pumping with low casing threshold. And the ultrasmall PC slab lasers monolithically grown on CMOS-compatible on-axis Is (001) substrates is presented, exhibiting single-mode operation with an ultraslow threshold ~ 0.6μW and a large spontaneous emission coupling efficiency ~ 18%. This work establishes a new route to form monolithic light sources for high-density optical interconnects in future large-scale photonics integrated circuits. Appendix A describes briefly the background of WGMs and PC structure. Epitaxial layers presented in this thesis are illustrated in Appendix C and D, showing the fabricated micro-LED and single mode PC slab microlasers operating at red emission region, respectively. 近年来,数据流量成指数级增长,需要一种更高效的片上光互连方法,该方法具有更低的能耗、更高的调制速度和更高的处理单元密度。因此,人们迫切需要一种体积小、功耗低、调制速度快的激光器,这种激光器可以用微型或纳米级激光器来实现。具有微腔结构的半导体微腔激光器以其低功耗、基于晶圆的工艺以及能够在单个芯片上实现与其他功能器件高密度集成的优势,已成为光子集成电路重要的光源元件。本论文以半导体量子阱或量子点为增益材料,探讨半导体微腔激光器的设计、制备及特性分析。第一章中介绍了本论文的研究背景。半导体微腔激光器的制备优化和特性表征的光路搭建将在第二章描述。第三章展示了所设计的新型微腔结构和激光器。接下来将介绍两种平台上的微腔激光器,一种是柔性微腔激光器,旨在探索柔性PIC方案(第四章和第五章)。另一种是直接生长在硅上的微腔激光器,它是低成本和高密度PICs的首选,这将在第六章中讨论。第七章将对以上工作作一个简短的总结,随后是四个相关附录。采用刻蚀方法制备了包括微盘、微环和光子晶体激光器在内的微腔激光器。利用电子束光刻技术设计器件的图形,并通过等离子体干法刻蚀方法将图形转移到半导体材料中。器件制备的详细程序和蚀刻优化,以及特性的光路搭建在第二章中进行了详细介绍。通过扫描电子显微镜、微区光致发光等方法研究了微腔激光器的特性,并对等离子体干法刻蚀工艺的优化进行了详细的讨论。将展示GaAs基微盘、PC微腔和InP-PC微腔的优化配方,获得了光滑的刻蚀表面和垂直的半导体微腔轮廓。在第三章中,提出了具有五重旋转对称性的五重PC微腔。与准光子晶体结构、三角形和方形光子晶体微腔类似,五重光子晶体结构的光子带隙的存在表明了它在超低阈值激光器等方面的潜在应用。此外,还提出了两种具有六个缺陷空气孔和一个缺陷空气孔的五重PC微腔。利用三维时限有限差分方法,证明了WGM、单极模和偶极子模等谐振缺陷模式的存在。高品质因子缺陷模的存在进一步说明了五重微腔具有广泛的应用前景。此外,基于红色区域发射InGaP/InGaAIP量子阱材料,设计和制备了悬臂梁基微环激光器。通过引入悬臂梁打破微环腔的旋转对称性,导致简并模分裂和单模激光发射。连接的悬臂梁不仅可以为微环激光器提供机械支撑,而且可以作为波导有效地提取光。同时,研究了悬臂梁微环激光器在折射率传感器和柔性局部应变计中的应用。柔性集成光子元件在柔性机器人和可穿戴器件等方面具有广阔的应用前景。在第四章中,将介绍超薄弯曲和柔性可见光波段激射的微盘激光器,它具有单模激光发射和高质量因子(~17000),能够实现WGMs的三维空间强度分布,并且与传统的二维平面内WGMs相比,为受限光子提供了额外的自由度,可以提供具有吸引力的三维曲面光子集成电路的光源。另外,在PDMS聚合物基片上嵌入了柔性可见微盘激光器和微环激光器,它们的光谱对柔性衬底的变形非常敏感。柔性微激光器也有望成为PICs和微型局部应变计的可调谐光源,具有低功耗的特点。在硅上集成成熟的III-V光子器件是实现高效Si基发光源的一个有效解决方案,因为IV族体材料具有间接带隙特性。本文探讨了硅基单片集成高性能微腔激光器的解决方案。描述了直接生长在硅上的亚波长尺度(直径~1.1μm)微盘激光器,在室温下具备低激光阈值并实现连续光泵浦工作。介绍了与CMOS工艺兼容的S i(001)衬底上单片生长的超小型PC激光器,具有超低的阈值~0.6μW和大的自发辐射耦合效率~18%。这项工作为未来大规模光子集成电路中高密度光互连提供了一条新的途径。附录A简要介绍了WGMs的北京和PC结构。附录B给出了本论文中所述器件的外延层结构。附录C和附录D展示了半导体微腔激光器的一些其他实验结果,分别展示了在红光波段工作的micro-LED和单模PC激光器。

LibraryUniversity Library
Location Theses & Dissertations Collection
Call NumberM.Phil. Z46 2020
Document TypeThesis
CollectionSchool of Science and Engineering
Recommended Citation
GB/T 7714
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周陶杰.pdf(19758KB)Thesis-- No AccessCC BY-NC-SA
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