球腔的表面散射损耗  

Surface Scattering Loss of a Spherical Microcavity

作　　者：俞骁翀 戴成龙 YU Xiaochong;DAI Chenglong(Key Laboratory of Mutiscale Spin Physics,Ministry of Education,Applied Optics Beijing Area Major Laboratory,Department of Physiscs,Beijing Normal University,Beijing 100875,China)

机构地区：[1]北京师范大学物理学系应用光学北京市重点实验室,多尺度自旋物理教育部重点实验室,北京100875

出　　处：《光子学报》2024年第5期138-148,共11页Acta Photonica Sinica

基　　金：国家自然科学基金(Nos.12104059,62131002);广东省基础与应用基础研究基金资助项目(No.2022A1515011475)。

摘　　要：以能够精确求解的球腔为例,利用等效电流方法,给出了随机粗糙表面对腔模的散射损耗的估计,并利用等效的随机散射点进行数值仿真。结果显示对于常见的高品质因子微腔中平缓的粗糙表面,散射主导的品质因子正比于腔半径和波长三次方、反比于表面方差以及相关长度平方。The ultra-high quality factor(typically above 107)of the whispering-gallery microresonators such as microsphere,microtoroid,microbubble is mainly due to the total-internal-reflection and ultra-smooth surface.Usually,higher quality factor corresponding to narrower linewidth and longer photon life-time,which strongly increase the light-matter interaction and sensing performance,makes those microresonators the perfect platform for the nonlinear optics and optical sensing research.To further optimize the quality factor,analysis and suppressing the main loss channels is needed.The loss in a whispering-gallery microresonator is mainly depends on absorption loss,scattering loss and radiation loss.Among them,the radiation loss of the resonator is more obvious for small cavity or lower refractive contrast,while the absorption loss and scattering loss from the bulk cavity material have less dependence with the cavity size.Since the fast development of fabrication techniques,the bulk absorption and scattering loss can be strongly suppressed,while the surface scattering loss trends to become dominant for large cavities.However,the previous estimations of surface scattering have a range covers several orders of magnitude,which also become unacceptable for meeting the requirement of further improvement.In this article,the surface scattering loss of a spherical microcavity with the tiny random surface roughness(far below the optical wavelength)is analyzed by applying the equivalent current method.The surface function of the microcavity is first transfer to the equivalent polarization current which excite the secondary modes.By combining the simplified total radiation power of the excited modes with the estimation of the surface field component,a more precise estimation of surface scattering loss is finally provided and further verified via numerical calculation.In detail,this equivalent current can be expressed as the superposition of two tangential fields and one radial field on surface of the microsphere.Among them,the transv

关 键 词：回音壁模式 微球腔 散射损耗 品质因子 等效电流 

分 类 号：O436.2[机械工程—光学工程]