基于溶胶凝股薄膜的新型片上氧化硅微型激光器

发布时间：2018-09-09 18:37

【摘要】：近些年来,光学谐振腔,特别是光学微腔具有较高品质因子和较小模式体积等优点,在许多领域越来越成为一个比较重要的研究热点,包括基础研究和应用研究,如腔光-力学、腔-量子电动力学、非线性光学、生物传感及微型激光器等方面。其中,利用高品质因子的光学微腔可以制得低阈值、窄线宽的激光器。通过光纤锥烧制而成的微球腔,其Q值接近1010。加州理工学院的Vahala研究组使用光刻、HF刻蚀、XeF2干法刻蚀、CO2激光回流等过程制备出回音壁模式氧化硅微环芯腔。氧化硅表面经热熔化处理因表面张力作用形成非常光滑的圆环形,其Q值可达4X108。本论文详细研究了回音壁模式光学微腔的制备及其在激光器方面的应用研究。通过溶胶凝胶法制备稀土掺杂的氧化硅光学微腔可得到低阈值的微型激光器。本论文主要包括如下几方面内容:1.研究了溶胶凝胶法于硅片表面制备氧化硅薄膜的工艺。通过改良溶胶凝胶法中各溶液组分的配比、陈化干燥时间及高温退火方式等因素,我们制备出致密无裂纹的氧化硅薄膜,厚度可在200 nm～2μm之间不等。通过在溶胶凝胶法过程中掺入任意种类及浓度的稀土元素,可制得不同掺杂浓度的氧化硅薄膜。实验表明,同等制备工艺情况下,随着掺杂浓度的增加,制备的氧化硅薄膜会变薄。为了得到不同掺杂浓度且厚度一致的氧化硅薄膜,不同掺杂浓度薄膜的制备工艺会略有不同。2.简要论述了微光纤的拉制工艺。详细讨论了回音壁模式光学微腔的制备过程,包括光刻、HF湿法刻蚀、XeF2干法刻蚀、CO2激光回流等过程。我们通过溶胶凝胶法制备出厚度约1.3 μm的掺铒氧化硅薄膜,随后制备出掺铒氧化硅微盘腔及微环芯腔。通过控制XeF2气体各向同性刻蚀硅柱的时间和速率,将硅柱的直径控制在5μm以内,随后经CO2激光回流后,我们第一次制得硅片集成的掺铒氧化硅微球腔。通过1480 nm波段的可调激光器共振激发三种光学微腔,我们都观测到了铒离子的上转换绿光。同时测得了掺铒微环芯腔和微球腔激光器的激光光谱,其中微球腔激光器的阈值可低至976 nW。3.利用溶胶凝胶法制得掺钕氧化硅薄膜,随后制备出不同尺寸不同钕掺杂浓度的氧化硅微环芯腔。通过780 nm波段可调激光器泵浦微腔,我们分别在910 nm和1064 nm波段测得激光光谱,阈值分别为108.5 μW和1.6μW。当采用非共振激发掺钕微腔时,我们同样在1064 nm波段测得激光光谱,阈值约137 μW。4.在溶胶凝胶法配制溶液时,我们掺入硝酸铥和硝酸钬,分别制备了不同浓度比例的掺铥氧化硅薄膜和铥钬共掺氧化硅薄膜,厚度均约为1.35μm。随后利用集成工艺,分别制备出掺铥微环芯腔和铥钬共掺微环芯腔。采用1.6 μm波段的可调激光器泵浦,我们测得掺铥微腔激光靠近2 μm附近的激光光谱,最低阈值约2.8 μW。同时,我们也测得铥钦共掺激光器在2 μm以上的激光光谱,最低阈值约2.7 μW。另外,当改变泵浦波长时,我们观测到不同颜色的荧光图像。
[Abstract]:In recent years, optical resonators, especially optical microcavities, have become more and more important research hotspots in many fields due to their advantages of high quality factor and small mode volume, including fundamental research and applied research, such as cavity opto-mechanics, cavity-quantum electrodynamics, nonlinear optics, biosensors and micro-lasers. Low threshold and narrow linewidth lasers can be fabricated by using high quality factor optical microcavities. The Q value of the microcavities fabricated by firing fiber cones is close to 1010. The Vahala research group of California Institute of Technology fabricated the echo wall mode silicon oxide microcavity by using photolithography, HF etching, XeF2 dry etching, CO2 laser reflux and so on. In this paper, the fabrication of the echo-wall mode optical microcavity and its application in lasers are studied in detail. The rare earth doped silicon oxide optical microcavity is prepared by sol-gel method, and a low threshold micro-laser can be obtained. The main contents of this paper are as follows: 1. The preparation technology of silicon oxide film on silicon wafer surface by sol-gel method is studied. By improving the composition of solution in sol-gel method, aging drying time and high temperature annealing method, we have prepared dense and crack-free silicon oxide film with thickness ranging from 200 nm to 2 micron. Silicon oxide thin films with different doping concentration can be prepared by adding any kind and concentration of rare earth elements into the sol-gel process. The experimental results show that under the same preparation process, with the increase of doping concentration, the prepared silicon oxide thin films will become thinner. The fabrication process of the doped thin films will be slightly different.2.The fabrication process of the microfiber is briefly discussed.The fabrication process of the microcavity in the echo-wall mode is discussed in detail,including photolithography,HF wet etching,XeF2 dry etching,CO2 laser reflux and so on.The erbium-doped silica thin films with thickness of about 1.3 micron are prepared by sol-gel method. Erbium-doped silicon oxide micro-disk cavity and micro-ring core cavity were fabricated. By controlling the time and rate of XeF2 gas isotropic etching the silicon column, the diameter of the silicon column was controlled within 5 micron. After CO2 laser reflux, we first fabricated the integrated Erbium-doped silicon oxide micro-disk cavity. In the optical microcavity, we have observed upconversion green light of erbium ions. Laser spectra of erbium-doped microcavity core cavity and microsphere cavity laser have also been measured. The threshold value of microsphere cavity laser can be as low as 976 nW.3. Neodymium-doped silicon oxide thin films were prepared by sol-gel method, and then different size and different concentration of neodymium-doped silicon oxide micro-rings were prepared. Core cavity. Pumped by a 780 nm tunable laser, the laser spectra were measured at 910 nm and 1064 nm, with thresholds of 108.5 and 1.6 mu W, respectively. The thickness of Tb-doped SiO_2 thin films and Tb-Ho co-doped SiO_2 thin films with different concentration ratios were about 1.35 micron. Then the Tb-doped and Tb-Ho co-doped micro-ring core cavities were fabricated by integrated technology. Using tunable laser pumping at 1.6 micron band, we measured that the Tb-doped micro-cavity laser was close to 2.5 micron. Laser spectra near micron have a minimum threshold of about 2.8 mu W. At the same time, we have also measured the laser spectra above 2 mu, and the minimum threshold is about 2.7 mu W. In addition, fluorescence images of different colors are observed when the pump wavelength is changed.
【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TN248

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