Research on Nonlinear Optics and its Applications in Whispering Gallery Mode Microresonators

回音壁模（WhisperingGalleryMode，WGM）光学微腔是一种环状结构的光学微腔，光子沿其内壁不断全反射而构成谐振模式。得益于腔体较低的材料损耗、辐射损耗以及散射损耗等，回音壁模微腔特别是由表面张力作用形成的微球腔、类微球腔等具有超高的品质因子。这种高品质因子结合微腔本身具备的小模式体积，可以显著地增强光子与物质的相互作用，从而使其非常适合腔量子电动力学、非线性光子学、微型传感器等领域的研究。本论文以高品质因子回音壁模微腔为载体，借助受激布里渊散射和四波混频等非线性过程，探讨微腔在低阈值布里渊激光器、光学频率梳（OpticalFrequencyComb，OFC）及其衍生的窄线宽微...Whispering gallery mode (WGM) optical microcavity is an optical microresonator with circular structure, where photons travel around its inner wall by all reflection. Benefiting from the low material loss, radiation loss and scattering loss of the cavity, WGM microresonators, in particular, the surface tension induced microspheres or microsphere-like ones possess ultrahigh quality factors. This ult...学位：工学博士院系专业：信息科学与技术学院_电子科学与技术学号：2312013015426

Ultralow-threshold laser and blue shift cooperative luminescence in a Yb3+ doped silica microsphere

An experimental investigation on ultralow threshold laser and blue shift cooperative luminescence (CL) in a Yb3+ doped silica microsphere (YDSM) with continuous-wave 976 nm laser diode pumping is reported. The experimental results show that the YDSM emits laser oscillation with ultralow threshold of 2.62 mu W, and the laser spectrum is modulated by the microsphere morphology characteristics. In addition, blue emission of YDSM is also observed with the increase of pump power, which is supposed to be generated by CL of excited Yb ion-pairs with the absorption of 976 nm photons and Si-O vibration phonons, and the process is explained with an energy level diagram. This property of the blue shift CL with phonons absorption in the Yb3+ doped microcavity makes it attractive for the application of laser cooling based on anti-Stokes fluorescence emission, if the Yb3+ doped microcavity made from with low phonon energy host materials. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License

SiO微盘腔的湿法腐蚀工艺研究

SiO回音壁模式（whispering gallery mode,WGM）的光学谐振腔具有品质因子Q值高、模式体积小、制作简单等优点,在腔量子电动力学、生物传感器、滤波器、非线性光学等领域具有非常好的应用前景.采用热氧化生长SiO、光刻图形化、磁控溅射生长Cr掩膜、HF缓冲液湿法腐蚀SiO、KOH溶液湿法腐蚀Si并去除Cr掩膜等工艺,得到了周期化、尺寸不同的SiO微盘腔,其直径分别为20,40和60μm.利用原子力显微镜表征微盘腔表面的粗糙度,均方根表面粗糙度仅为0.469nm.在未经任何表面处理或者激光处理的情况下,利用连续波长可调激光器,通过光纤锥与微盘腔耦合,透射谱测量得到微盘腔的自由光谱范围（free spectrum range,FSR）为λFSR=9.6nm,Q值约为1×10.中航工业产学研项目(CXY2011XD24)；中国博士后科学基金(2015M582041)

Luminescent properties of Er~(3+)/Yb~(3+) co-doped oxyfluoride glass ceramic microsphere with the tapered fiber-microsphere coupling system

采用高温煅烧法制备了Er3+/yb3+共掺的氟氧玻璃陶瓷新材料(41.2SIO2-29.4Al2O3-17.6nA2CO3-11.8lAf3-0.5Erf3-2.5ybf3),并制作了透明带柄微球.提出了用锥光纤微球耦合系统研究Er3+/yb3+共掺的氟氧玻璃陶瓷材料发光特性的新方法.它具有所需激发光功率低、制备简便和便于测试的特点.用锥光纤作为耦合器将976 nM激光高效耦合入微球,并将产生的荧光和激光耦合出微球输到光谱分析仪,测量到了强的522,545和657 nM上转换荧光,也测到Er3+产生的1562 nM激光振荡光谱图.分析了Er3+/yb3+共掺氟氧玻璃陶瓷微球中Er3+上转换发光的机理、发光效率高的机理,分析了在氟氧玻璃陶瓷微球中产生激光振荡阈值比在SIO2基质微球中高的机理.We prepare Er3+/Yb3+co-doped oxyfluoride glass ceramic samples by high temperature calcination method(41.2SiO2-29.4Al2O3-17.6Na2CO3-11.8LaF3-0.5ErF3-2.5 YbF3), and also fabricate transparent microspheres each with a handle.We propose a new method of studying the luminescent properties of Er3+/Yb3+co-doped oxyfluoride glass ceramic with the tapered fiber-microsphere coupling system.The method has characteristics such as low excitation optical power, easy preparation and testing.We couple the 976 nm laser into the microspheres with the coupler of optical tapered fiber, then the fluorescence and laser are connected to spectrum analyzer with the optical tapered fiber.The strong up-conversion fluorescences at 522, 545 and 657 nm are obtained, and the laser oscillation spectra generated by Er3+ions at 1562 nm are also measured.The up-conversion luminescence mechanism of Er3+, the mechanism of high luminescence efficiency in Er3+/Yb3+co-doped oxyfluoride glass ceramic microsphere, and the mechanism of higher laser oscillation threshold in the oxyfluoride glass ceramic microsphere than in the SiO2matrix microsphere are all analyzed

Study on luminescent properties of Yb~(3+)-doped phosphosilicate microsphere

本文采用双锥光纤与微球腔耦合系统研究成分为55.93P2O5-3.57Al2O3-15nA2CO3-20SIO2的掺yb3+磷硅酸盐微球腔的合作上转换发光、下转换激光振荡及其级联拉曼激光振荡等发光特性.本实验采用中心波长为976 nM、线宽为0.15 nM的单纵模半导体激光作为抽运光源,在掺yb3+磷硅酸盐微球腔中测得中心波长为476.1 nM的蓝色合作上转换荧光,并运用合适的理论模型来解释该合作上转换产生11.9 nM蓝移效应的原因.同时,在1058.26 nM和1060.02—1126.08 nM处分别测得了由于微球腔谐振产生的下转换单纵模及多纵模激光振荡.另外,本文首次在同一微球腔中测得了由yb3+下转换激光激发产生的多级级联拉曼激光.在抽运功率为8.53 MW时,产生的级联拉曼激光可以达到两级,且波长延伸至1300 nM附近.Cooperative luminescence, down-conversion laser oscillation and cascaded Raman laser in Yb3+-doped 55.93P2O5-3.57Al2O3-15Na2CO3-20SiO2 phosphosilicate glass are studied in the biconical fiber-microsphere coupling system in this paper.A single-mode semiconducter laser with the center wavelength at 976 nm and line-width 0.15 nm is used as a pump source.The blue-shifted cooperative luminescence centered at 476.1 nm is obtained in the Yb3+-doped phosphosilicate microsphere.And a suitable model may be applied to explain the reason for the 11.9 nm blue-shift in this process.Meanwhile, the single-mode laser(at 1058.26 nm) and multimode laser oscillations(from 1060.02 to 1126.08 nm) have also been obtained as the result of resonant oscillation in microsphere cavity.In addition, for the first time so far as we know a self-stimulated cascaded Raman laser is observed in the same phosphosilicate microsphere, which is generated by the down-conversion laser of Yb3+.When the pump power is 8.53 mW, a two-order cascade Raman laser is generated,which extends the laser wavelength to near 1300 nm

Luminescent properties of Er3+/Yb3+ co-doped oxyfluoride glass ceramic microsphere with the tapered fiber-microsphere coupling system

We prepare Er3+/Yb3+ co-doped oxyfluoride glass ceramic samples by high temperature calcination method (41.2SiO2-29.4Al2O3 - 17.6Na2CO3-11.8LaF3 - 0.5ErF3-2.5 YbF3), and also fabricate transparent microspheres each with a handle. We propose a new method of studying the luminescent properties of Er3+/Yb3+ co-doped oxyfluoride glass ceramic with the tapered fiber-microsphere coupling system. The method has characteristics such as low excitation optical power, easy preparation and testing. We couple the 976 nm laser into the microspheres with the coupler of optical tapered fiber, then the fluorescence and laser are connected to spectrum analyzer with the optical tapered fiber. The strong up-conversion fluorescences at 522, 545 and 657 nm are obtained, and the laser oscillation spectra generated by Er3+ ions at 1562 nm are also measured. The up-conversion luminescence mechanism of Er3+, the mechanism of high luminescence efficiency in Er3+/Yb3+ co-doped oxyfluoride glass ceramic microsphere, and the mechanism of higher laser oscillation threshold in the oxyfluoride glass ceramic microsphere than in the SiO2 matrix microsphere are all analyzed. ? 2014 Chinese Physical Society

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel

JUNO sensitivity on proton decay p → ν K + searches*

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this study, the potential of searching for proton decay in the $p\to \bar{\nu} K^+$ mode with JUNO is investigated. The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar{\nu} K^+$ is 36.9% ± 4.9% with a background level of $0.2\pm 0.05({\rm syst})\pm$$0.2({\rm stat})$ events after 10 years of data collection. The estimated sensitivity based on 200 kton-years of exposure is $9.6 \times 10^{33}$ years, which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies