回音壁模式微腔的耦合特性与封装技术研究

发布时间：2018-03-04 07:36

  本文选题：回音壁模式　切入点：光学谐振腔　出处：《中国科学技术大学》2016年博士论文　论文类型：学位论文

【摘要】：近年来,回音壁模式(Whispering Gallery Mode, WGM)光学微腔因其极高的品质因子(Quality factor,Q值)和极小的模式体积(V)得到了很大的关注,它们在诸多领域比如基础物理理论研究以及实用化光电子器件(光开关、光调制器、极窄线宽滤波器和高灵敏度传感器等)领域都具有非常大的应用潜力。尽管如此,目前它们基本还仅限于实验室研究,并没有走向实用化或商品化。很重要的原因是WGM的谐振特性受外界环境的影响非常大。首先,吸附到微腔表面的水汽或者微小灰尘颗粒会严重降低系统的Q值；其次,WGM的谐振波长易受外界温度变化的影响而产生偏移。这些都会导致基于微腔的传感器的性能下降,并阻碍微腔的实用化。另外,为了获得较高的耦合效率,通常使用锥形光纤来激发微腔中的谐振模式,这会导致整个耦合系统非常脆弱且缺乏健壮性,外部极小的振动甚至微弱空气流动都可能引起WGM耦合状态的显著变化。以往的研究中,人们在封闭的环境中进行实验,以保证微腔周边干净的环境以及稳定的气流。这种方式虽然可以极大限度的排除污染物的干扰以及温度噪声的影响,但巨大的密闭容器以及分立的耦合结构使得整个系统非常笨重、复杂,不便于应用在实际环境中。为了促进微腔耦合系统的实用化,需要设计一种合适的封装结构。针对以上问题,本论文提出了一些解决方案,论文内容大体上可以分为两大部分：理论仿真和实验。首先,利用FDTD方法以及COMSOL软件的PDE求解器,研究了具有内参考功能的三层结构微球腔的耦合特性和传感性能,仿真结果说明我们提出的这种新型结构的传感器不仅能够降低折射率传感中的热噪声影响,还能同时探测温度的变化。然后,我们实验研究了微球腔、柱形腔和瓶口腔的耦合特性,将它们封装成为了一体化的器件,并进行了温度传感实验以及抗振动性能的测试。详细的研究内容如下：(1)基于FDTD方法,实现了三层结构微球腔与光波导耦合的仿真,三层膜的折射率从内到外依次为高、低、高。研究了膜层厚度对谐振特性的影响,发现只要三个膜层所选择的折射率以及厚度合适,内外两个高折射率膜层能够束缚光波并支持它们各自的WGM。另外,我们还研究了微腔外的环境折射率变化对内外层WGM谐振特性的影响,仿真结果说明：环境折射率变化时,外层模式的谐振波长会显著改变,但内层模式的谐振波长变化非常小,这个性质使得三层结构微腔在高精度折射率和温度传感领域有重要的应用价值。(2)利用COMSOL软件的弱解型偏微分方程模块实现了微腔中谐振模式的稳态仿真计算,并利用微扰理论,推导出了三层微腔的内外层谐振模式用于温度和折射率传感的灵敏度表达式。我们发现,内外层两模式的温度响应特性非常接近,但它们对外界折射率变化的响应差异巨大。详细研究了膜层厚度对内外层模式的影响,通过优化最外层的厚度,理论上实现了温度噪声的完美去除。(3)使用一种全新的封装方案加工出了微腔与锥形光纤耦合系统的一体化器件,借助一个石英玻璃管、两片石英玻璃以及紫外光固胶,在不改变己经调谐好的耦合状态的前提下完成了器件的封装。实验中,让微球腔与锥形光纤保持接触,以提高耦合系统的稳定性,这种情况下依然获得了高达1.08x108的Q值。我们研究了微球腔取向和位置对谐振谱的影响,发现通过调整微球腔的位置以及取向可以获得不同的谐振谱。将封装器件密封在一个干净的有机玻璃制作的盒子中,获得了Q值的长时间保持。另外,我们还制作了双光纤耦合微球腔的封装器件,可以应用于Add-Drop滤波器,制作出的器件参数为：Q值达到2.7×10。,FSR约为0.016nm,最大Drop口输出为42%。(4)通过光纤熔接机的电弧放电,我们制作出了高质量的柱形腔和瓶口腔,在不同的耦合点实现了腔内谐振模式的选择性激发。在数值仿真以及理论计算的帮助下,获得了谐振模式的空间场分布,实现了谐振模式的定位识别,与实验结果非常吻合。另外,通过轴向移动微腔,实现了谐振模式的可控、稳定的耦合。最后,我们采用与微球腔同样的封装方法,对柱形腔以及瓶口腔进行了一体化封装。由于柱形腔直径的均匀性,模式场的分布在轴向上被显著拉长,因此柱形腔封装器件的抗振动性能远远优于微球腔器件。我们相信这种便携的、具有良好健壮性的微腔器件将来会得到广泛的应用,尤其在振动环境场合。
[Abstract]:In recent years, the echo wall mode (Whispering Gallery Mode, WGM) optical micro cavity because of its high quality factor (Quality, factor, Q) and the minimal volume model (V) has received much attention in many fields, such as the physical basis of their theoretical research and practical optoelectronic devices (optical switch, optical modulator. Narrow linewidth filter and high sensitivity sensor) field has great potential. However, they are only limited to present basic laboratory research, and there is no practical or commercial. An important reason is that the resonant characteristics of WGM influenced by the external environment is very large. First of all, the water vapor adsorption to micro cavity the surface or tiny dust particles would seriously reduce the Q value of the system; secondly, influence the resonant wavelength of WGM are vulnerable to external temperature changes and shifts. These will lead to the performance of sensor based on micro cavity Fall, and hinder the practicality of the micro cavity. In addition, in order to obtain high coupling efficiency, usually using tapered fiber to excite the resonant microcavity, which will lead to the whole coupling system is very weak and lack of robustness, minimal external vibration even weak air flow may cause significant changes in the WGM coupling state. In the past in the study, people were in a closed environment, in order to ensure the air cavity surrounding the environment clean and stable. Although this method can eliminate the maximum effect of pollutants and noise interference temperature, but the huge airtight container and a coupling structure of separation of the whole system is very cumbersome, complex, not easy to use in the actual environment. In order to promote the microcavity coupling system is practical, need to design a suitable package structure. To solve the above problems, this paper puts forward some solutions The content of the scheme, can be divided into two parts: theoretical simulation and experimental results. First, using the FDTD method and the PDE solver of COMSOL software, the coupling characteristics and sensing properties of the three layer structure of microsphere cavity with internal reference function, the simulation results show that the new sensor structure we propose not only to reduce the the refractive index of thermal noise in the sensor, but also detect the change of temperature. Then, we study the microsphere cavity, coupling characteristics of the cylindrical cavity and a bottle mouth, encapsulating them into an integrated device and a temperature sensing experiment and test of anti vibration performance. The detailed contents are as follows: (1) based on the FDTD method, the simulation of the three layer structure of microsphere cavity and waveguide coupling, three film refraction rate from the inside to the outside are high, low and high. On the film thickness on the resonant characteristic The influence of three, found that as long as the choice of film refractive index and thickness of the right, and two high refractive index film capable of binding light and support their WGM. in addition, we also study the micro cavity environment refraction rate changes influence on the resonant characteristics of inner and outer layer of WGM, the simulation results showed that the change of ambient refractive index when the resonant wavelength of outer model will change significantly, but the change of inner mode resonant wavelength is very small, this property makes the three layer structure of micro cavity has important application value in the high precision of refractive index and temperature sensing. (2) the use of COMSOL software for weak solutions of partial differential equations to achieve steady-state simulation of micro module the cavity resonance mode is calculated, and by using the perturbation theory, deduces the inner and outer layer of resonant modes for the sensitivity expression of refractive index and temperature sensing micro cavity three. We found that the inner and outer layer two mode temperature The degree of response is very close, but the difference of their response to external refractive index change is huge. The effects of thickness of inner layer pattern research in detail, through the optimization of the thickness of the outer layer, the theory to achieve the perfect temperature noise removal. (3) using a new package processing integration device of micro cavity with the tapered fiber coupling system, by means of a quartz glass tube, two pieces of quartz glass and UV curable adhesive, without changing the premise has been tuned coupling state under well finished package. In the experiment, let the microsphere cavity and the cone shaped fiber contact, in order to improve the stability of the coupling system, this kind of situation still get up to 1.08x108 Q. We study the orientation and position of microsphere cavity resonance spectrum, found by adjusting the position and orientation of the microsphere cavity can obtain different resonance spectrum. The package The sealing device in a clean organic glass box, the long time the Q value maintained. In addition, we also made the package double optical fiber coupling cavity, can be applied to the Add-Drop filter device parameters produced: Q value reached 2.7 * 10., FSR is about 0.016nm, the largest Drop output is 42%. (4) arc discharge by optical fiber fusion splicer, we produce high quality cylindrical cavity and a bottle mouth, at different coupling point to achieve the selective cavity resonance mode excitation. In the calculation of numerical simulation and theory under the help of the resonant mode field distribution is obtained to achieve recognition of resonant modes, in good agreement with the experimental results. In addition, the axial movement of micro cavity, the controllable resonant mode, stable coupling. Finally, we use the same and microsphere encapsulation method, the cylindrical cavity and mouth Cavity of a integrated package. Because the cylindrical cavity diameter uniformity, mode field distribution is significantly elongated in the axial direction, so the vibration resistance of cylindrical cavity package is far better than that of microsphere cavity devices. We believe that this kind of portable, microcavity device has good robustness will get extensive application. Especially in the environment of vibration occasions.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN253
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本文编号：1564761