回音壁模式光学微腔的拉曼调制及其应用

发布时间：2018-10-18 11:06

【摘要】：回音壁模式光学微腔由于具有高品质因子、低模式体积和良好的可集成性,在高灵敏度传感器、非线性光学、微型激光器、光信息处理、腔光力学和量子信息等领域取得了重要的发展和应用。为提升微腔的品质因子等性能,人们在微腔中掺杂稀土离子等光学增益材料制成主动腔。然而主动腔的制作过程相对复杂,而且其泵浦光源和工作范围受到稀土离子等掺杂物质的泵浦带和发光带的限制。因此我们试图以微腔材料中普遍存在的拉曼过程代替增益物质的掺杂,减除额外的加工成本,避免掺杂引入的微腔损耗,同时放宽对泵浦激光和工作范围波长的限制。本论文围绕回音壁模式光学微腔的拉曼调制,主要开展了以下三方面的研究:一、利用回音壁微腔拉曼激光检测纳米粒子。我们同美国圣路易斯华盛顿大学的杨兰教授的研究组合作,利用二氧化硅回音壁微腔的拉曼增益补偿微腔损耗,提升粒子检测的分辨率,并通过微腔拉曼激光模式劈裂产生的自参照的拍频,实现了对半径低至10 nm的单个纳米粒子的检测和计数。实验达到了创纪录的极化率灵敏度(3.82×106μm3)。二、通过拉曼增益调控回音壁微腔系统的耦合机制。我们从理论和实验上研究了不同耦合条件下,波导耦合的回音壁微腔的透射谱随拉曼增益的变化。实验显示拉曼增益的大小不仅影响着透射谱的线宽,还能改变系统的耦合机制。在此基础上,我们通过施加拉曼增益,在不移动任何单个光学元件的前提下,实现对微腔-波导系统耦合机制的连续调控。这种调控达成了此前类似方法无法实现的从欠耦合向过耦合方向的调节,还在调控过程中提高了谱线的分辨率,对光学微腔系统的双向全光调节具有重要意义。三、利用二氧化硅的受激拉曼损耗调控回音壁微腔系统的耦合机制。我们首次研究了二氧化硅的受激拉曼损耗对回音壁微腔系统的影响,并在此基础上利用逆拉曼散射改变了微腔腔内损耗,实现了对光纤锥耦合的微芯圆环腔系统耦合机制的全光调节。我们在不改变微腔或光纤锥位置的前提下,通过注入低功率的泵浦光,将系统由深度过耦合调控到临界耦合。实验中共振透射率降低了19.58dB,远高于此前硅微环腔达到的9dB的对比度,而且相比硅微环腔,本方案不受双光子吸收和自由载流子吸收等效应的干扰。
[Abstract]:Echo wall mode optical microcavity has high quality factor, low mode volume and good integration, in high sensitivity sensor, nonlinear optics, micro laser, optical information processing, Cavity optics and quantum information have been developed and applied. In order to improve the quality factor and other properties of the microcavity, the active cavity is made by doping rare earth ions and other optical gain materials in the microcavity. However, the fabrication process of active cavity is relatively complex, and its pump source and working range are limited by the pump band and luminescent band of rare earth ions and other doped materials. So we try to replace the gain material doping with the Raman process which is widely used in the microcavity material, reduce the extra processing cost, avoid the microcavity loss caused by doping, and relax the restrictions on the pump laser and the operating range wavelength. In this thesis, we focus on the Raman modulation of echo-mode optical microcavity, which is mainly studied in the following three aspects: first, using the resonator Raman laser to detect nanoparticles. We are working with Professor Yang Lan of Washington University in St. Louis, USA, to use the Raman gain of the silicon dioxide echo wall microcavity to compensate for the loss of the microcavity and to improve the resolution of particle detection. By using the self-reference beat produced by the mode splitting of micro-cavity Raman laser, the detection and counting of a single nanoparticle with a radius of as low as 10 nm is realized. The experiment has achieved a record polarizability sensitivity (3.82 脳 106 渭 m ~ 3). Secondly, the coupling mechanism of the microcavity system is regulated by Raman gain. We have theoretically and experimentally studied the variation of the transmission spectrum of the waveguide coupled echo microcavity with the Raman gain under different coupling conditions. The experimental results show that the Raman gain not only affects the linewidth of the transmission spectrum, but also changes the coupling mechanism of the system. On this basis, we realize the continuous control of the coupling mechanism of microcavities and waveguides without moving any single optical element by applying Raman gain. This kind of regulation not only achieves the adjustment from undercoupling to over-coupling, but also improves the resolution of spectral lines in the process of regulation, which is of great significance to the bi-directional all-optical modulation of optical microcavity system. Thirdly, the coupling mechanism of microcavity system of echo wall is regulated by stimulated Raman loss of silicon dioxide. The effect of stimulated Raman loss of silicon dioxide on the microcavity system of echo wall is studied for the first time, and on this basis, inverse Raman scattering is used to change the loss of microcavity. The all-optical adjustment of the coupling mechanism of the microcore ring cavity system with fiber conical coupling is realized. Without changing the position of microcavity or fiber cone, the system is controlled from deep over-coupling to critical coupling by injecting low power pump light. The resonant transmittance is reduced by 19.58 dB, which is much higher than the contrast of 9dB achieved by the silicon microring cavity. Compared with the silicon microring cavity, the scheme is not interfered by the effects of two-photon absorption and free carrier absorption.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O43

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