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题名	利用飞秒激光直写制备三维回音壁模式光学微腔及其应用
作者	林锦添
学位类别	博士
答辩日期	2014
授予单位	中国科学院上海光学精密机械研究所
导师	程亚
关键词	光学微腔 超快光学 激光微加工 微光学 透明介质
其他题名	Three-dimensional whispering-gallery-mode microcavities fabricated on glass and crystal by femtosecond laser direct writing and their applications
中文摘要	回音壁模式光学微腔通过光在腔体材料与周围环境之间的光滑的圆形界面上的连续全反射，把光长时间地约束在微小的空间内，具有很高的品质因子(Q)与很小的模式体积。长的光子寿命、强的空间约束，可以极大地增强光与物质的相互作用，使得微腔在基础研究与工程应用上具有强烈的吸引力，具体的应用包括低阈值激光、非线性光学、量子物理、生物传感、光机械力学等等。当前芯片上的回音壁模式光学微腔，比如微盘、微芯环腔、变形微腔，主要借助传统的半导体平面制备方法，依赖于化学腐蚀选择性去除材料。尽管平面光刻等半导体工艺具有快速、低成本的优势，然而对于全三维微结构的制备，需要诸如层叠、键合等复杂步骤，让它难以（假如不是完全不可能），直接制备三维微腔。此外，也只有少数的材料能被用于光刻。这对相对于衬底倾斜进行光耦合或者提取、灵活地利用微腔腔体材料性质实现多样化的光子学目的等应用或研究，造成了障碍。因此需要开发新的方案来解决这些问题。 随着超快光学的发展，飞秒激光微加工以其突破衍射极限的加工精度和具有对透明材料内部进行三维加工的能力，已成为诸如微光学、微流体、微电子、基于聚合物的微腔等三维微结构不可或缺的制备技术。而透明的介质材料，比如玻璃、光学晶体等，一般具有宽的透射窗口和低的本征吸收损耗，成为构建高品质微腔的理想工作介质。尽管飞秒激光微加工技术已经在透明材料上制备三维微结构显示出很大的灵活性，但其受限的加工精度、大的表面粗糙度等不足，仍然亟待解决。本文致力于解决上述所提及的问题，利用飞秒激光微加工技术在玻璃与晶体上制备了高品质的三维回音壁模式光学微腔，主要内容包括： 1. 利用飞秒激光微加工技术首次在玻璃衬底上制备了高品质的三维回音壁模式微腔，其制备步骤包括通过飞秒激光构图选择性去除材料而形成由细支柱所支撑的独立微盘、二氧化碳激光回流提高微腔表面的光滑度。石英玻璃微腔与钕玻璃微腔的品质因子在1550 nm波段皆超过106。在室温条件下通过自由空间光学激励，钕玻璃微腔在1060 nm中心波长实现了低阈值69 µW的激射。这种形状可控的微腔可提供光场输出方向的自由度。该方法可以拓展到到石英玻璃与具有特殊光学性质的非二氧化硅透明介质（比如稀土掺杂玻璃、非线性光功能玻璃）上制备高品质的三维微腔； 2. 利用水辅助的飞秒激光刻蚀技术制备了尺寸小于50 µm的氟化钙晶体微盘结 构，再用聚焦离子束研磨微腔的侧壁，形成超光滑的微腔侧壁，其品质因子超过104；经水辅助的飞秒激光刻蚀、聚焦离子束研磨、化学腐蚀各向同性去除二氧化硅层、高温热退火，制备了700 nm厚的铌酸锂单晶微盘腔，测得其品质因子达到1.6×105，是同类铌酸锂微盘腔报道的最高值，并用宽谱的飞秒激光通过光纤锥泵浦，在5.04 mW泵浦功率条件下，实现了转换效率为1.04×10-5转换效率的倍频效应。晶体微腔可以作为紧凑的频率转换器、单光子源集成到光子回路上。
英文摘要	Whispering-gallery-mode (WGM) microcavities, which confine light via continuous total internal reflection along a smooth equatorial boundary between the dielectric cavity and surrounding, exhibit very high quality (Q) factor and small mode volume. The long photon lifetime and strong spatial confinement make them excellent candidates for low threshold nonlinear optics, quantum physics, low threshold lasing, and biosensing, and so on. Today, the most microfabricarion processes of on-chip WGM microcavities, such as microdisks, microtoroids, and deformed microcavities are based on planar lithographic approach, depending on the chemical selective material removal. Although the planar lithography is rapid and cost effective, it is difficult if not possible to form three-dimensional (3D) microcavities directly. Complicatied processes consisted of multilayer stacking and bonding, are required when it comes to 3D multifunctional integration. Furthermore, this approach is limited to a few lithographically enable materials. These make obstacles for many applications that prefer out-of-plane light coupling or extraction respect with substrates and microcavity substrate material flexibility to offer diverse photonic purposes, respectively. Therefore, there is a need to develop new strategies to overcome these problems. Recently, femtosecond laser micromachining has been proved as a promising solution for fabrication of flexible 3D microstructures, such as microoptics, microfluidics, and polymer-based microcavities. Wide transparent window and low intrinsic absorption loss make dielectric material, such as crystal and amouphous glass, ideal substrate materials for high-Q microcavity applications. Although femtosecond laser micromachining has shown flexibility for fabrication of 3D microstructures in bulk dielectric material, major issues still exist, such as the limited fabrication resolution, high surface roughness, and so on. In an effort to address these problems, we have developed a method to fabricate 3D microcavities in amorphous glass and crystalline material by femtosecond laser micromachining, followed by surface smooth process. Specifically, we demonstrate the fabrication of 3D high-Q microcavities on fused silica wafer that may have the light output from optical mode on an arbitrary plane respect to the substrate plane, microlaser with low threshold based on Nd:glass microcavity, and crystalline microcavities, as followed: First, a method is proposed to fabricate 3D microcavities on glass chip. The main fabrication procedures include the formation of on-chip freestanding microdisk supported by thin pillar through selective material removal by femtosecond laser patterning, followed by surface CO2 laser reflow for surface smoothing. Both the Q factors of fused silica microcavity and Nd:glass microcavity are measured to be higher than 106 at~1550 nm. The microlaser based on Nd:glass microcavity is operating at the wavelength of 1060 nm via free space optical excitation at room temperature at the threshold as low as 69 µW. These shape-controllable microcavities can provide the freedom of the output of the optical field. This technique offers potential for fabrication of high-Q microcavities on silica or non-silica dielectric substrates of vaious novel optical properties (e.g., rare earth ions doped glasses and nonlinear functional materials) with 3D geometries. Second, on-chip calcium fluoride (CaF2) microdisk resonators with size smaller than 50 µm are created by water-assisted femtosecond laser micromachining, followed by FIB milling to create ultra-smooth sidewalls. The Q-factors of the microresonators are measured to be higher than 104 at wavelengths near 1550 nm. Then, we report on fabrication of high Q lithium niobate (LN) WGM microresonators suspended on a silica pedestal by femtosecond laser microfabrication. The 55 μm-diameter microdisk resonator owns the Q factor of 1.6×105. This value is the highest reported to date for the same kind of on-chip LN microdisk resonators. Moreover, the experimental observation of second-harmonic generation in the on-chip LN microdisk resonator is demonstrated. A fiber taper is employed to couple with the microresonator, resulting in conversion efficiency η=1.04×10-5 when the pump power is 5.04 mW. Crystalline microcavities can be integrated in photonic circuits as compact frequency convertors, sources of single photons.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15885]
专题	上海光学精密机械研究所_学位论文
推荐引用方式 GB/T 7714	林锦添. 利用飞秒激光直写制备三维回音壁模式光学微腔及其应用[D]. 中国科学院上海光学精密机械研究所. 2014.

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