Theoretical calculation of fiber cavity coupling silicon carbide membrance

Ji-Yang Zhou,Guang-Can Guo,Chuan-Feng Li,Qiang Li,Jin-Shi Xu

doi:10.7498/aps.71.20211797

Abstract

Single spin color centers in solid materials are one of the promising candidates for quantum information processing, and attract a great deal of interest. Nowadays, single spin color centers in silicon carbide, such as divacancies and silicon vacancies have been developed rapidly, because they not only have similar properties of the NV centers in diamond, but also possess infrared fluorescence that is more favorable for transmission in optical fiber. However, these centers possess week fluorescence with broad spectrum, which prevents some key technologies from being put into practical application, such as quantum key distribution, photon-spin entanglement, spin-spin entanglement and quantum sensing. Therefore, optical resonator is very suitable for coupling centers to filter their spectrum and enhance the fluorescence by Purcell effect. It is very advantageous to use the fiber end face as cavity mirrors, thereby the fiber can provide small cavity volume corresponding to a large enhancement in spin color centers, and collect the fluorescence in cavity simultaneously, which has no extra loss in comparison with other collection methods. In this work, the properties and performance of fiber Fabry-Perot cavity coupling silicon carbide membrane are mainly studied through theoretical calculation. Firstly, some parameters are optimized such as membrane roughness and mirror reflection by calculating the mode of the fiber cavity and enhancing the color centers coupling into the cavity, then analyzing the properties of different modes in cavity, the enhancement effect on cavity coupling color centers, and other relevant factors affecting the cavity coupling color centers. Next, the influences of dominated factor and vibration on the properties of the cavity, the enhancement and outcoupling of centers coupled into the cavity are investigated, and finally the optimal outcoupling efficiency corresponding to different vibration intensities is obtained. These results give direct guidance for the further experimental design and direction for optimization of the fiber cavity coupling color centers.

Highlights

摘要半导体材料中的自旋色心是量子信息处理的理想载体,引起了人们的广泛兴趣。近几年,研究发现碳化硅材料中的双空位、硅空位等色心具有与金刚石中的氮-空位色心相似的性质,而且其荧光处于更有利于光纤传输的红外波段。然而受限于这类色心的荧光强度和谱线宽度,它们在量子密钥分发和量子网络构建等方面的实际应用依然面临严峻的挑战。利用光学腔耦合自旋色心实现荧光增强和滤波将能有效解决这些难题。将光纤端面作为腔镜,并与自旋色心耦合可以实现小模式体积的腔耦合, 而且天然地避免了需要再次将荧光耦合进光纤而造成损耗的缺点。本文理论计算了耦合碳化硅薄膜的光纤腔的性质和特征。首先通过优化各项参数包括薄膜表面粗糙度,腔镜反射率等,理论分析了存在于光纤腔中的不同模式的特点,以及光纤腔耦合色心的增强效果及相关影响因素。进一步地我们还研究对开放腔而言最主要的影响因素--振动对腔性质、色心的增强效果以及耦出效率的影响,最终得到在不同振动下的最大增强效果以及对应的耦出透射率。这些结果为今后光纤腔耦合色心的实验设计提供了最直接的理论指导,为实验的发展和优化指明了方向。关键词:自旋色心,光纤腔,碳化硅薄膜 PACS:03.67.-a, 61.72.jn,42.50.Pq
FFPC sketch, spectrum and field intensity of cavity, top left insets of (c) and (d) are the enlarged field on the surface: (a) Sketch of FFPC coupling membrane; (b) Spectrum of the fundamental mode varying with cavity length, tm is 4.12 μm. (c) Field intensity of the “air-mode” in cavity, tm is 4.29 μm. (d) Field intensity of the “membrane-mode” in cavity, tm is 4.19 μm
The point of intersection between the curve and dotted line indicates the cavity is in the membrane mode: (a) β factor of high fineness cavity with 0.025e-3 LM,a and 0.03e-3 LM,m; (b) β factor of low fineness cavity with 4.5e-3 LM,a and 4.5e-3 LM,m

Summary

Introduction

摘要半导体材料中的自旋色心是量子信息处理的理想载体,引起了人们的广泛兴趣。近几年,研究发现碳化硅材料中的双空位、硅空位等色心具有与金刚石中的氮-空位色心相似的性质,而且其荧光处于更有利于光纤传输的红外波段。然而受限于这类色心的荧光强度和谱线宽度,它们在量子密钥分发和量子网络构建等方面的实际应用依然面临严峻的挑战。利用光学腔耦合自旋色心实现荧光增强和滤波将能有效解决这些难题。将光纤端面作为腔镜,并与自旋色心耦合可以实现小模式体积的腔耦合, 而且天然地避免了需要再次将荧光耦合进光纤而造成损耗的缺点。本文理论计算了耦合碳化硅薄膜的光纤腔的性质和特征。首先通过优化各项参数包括薄膜表面粗糙度,腔镜反射率等,理论分析了存在于光纤腔中的不同模式的特点,以及光纤腔耦合色心的增强效果及相关影响因素。进一步地我们还研究对开放腔而言最主要的影响因素--振动对腔性质、色心的增强效果以及耦出效率的影响,最终得到在不同振动下的最大增强效果以及对应的耦出透射率。这些结果为今后光纤腔耦合色心的实验设计提供了最直接的理论指导,为实验的发展和优化指明了方向。关键词:自旋色心,光纤腔,碳化硅薄膜 PACS:03.67.-a, 61.72.jn,42.50.Pq. 中也发现了性质优良的色心,由于 SiC 材料具有丰富的晶格构型,其包含的色心种类也十分丰富。当前最常研究的是 4H-SiC 中的双空位(divacancy,简记为 VSiVC) 色心,即晶格中缺失一个 Si 原子和一个邻近 C 原子的两个晶格空位组成的点缺陷,共有四种类型,分别命名为 PL1,PL2,PL3 以及 PL4,另外还存在 PL5、 PL6 和 PL7 等特殊结构的 VSiVC 色心[18,19,20,21,22,23]。这些色心具备与金刚石 NV 色心相似的性质,如 c 轴色心(PL1, PL2, PL6)都具备 C3v 对称性[24],自旋 S = 1[25, 26],三能级结构[27, 28],能够光初始化和读出[29],同样是宽谱弱荧光[22, 30]等,但是 4H-SiC 中的这些 VSiVC 色心荧光处于红外波段(1100 nm 附近),相比 NV 色心可见波段 (637 nm 附近)具有更低的光纤传输损耗(前者是 0.7 dB/km,后者是 8 dB/km), 更适合远距离通信和活体传感等。因此将 FFPC 与 4H-SiC 中的 VSiVC 结合是该类自旋色心在量子信息技术应用上的发展路线之一[31]。 (membrane-mode)[33],分别满足关系: νa ma c 2ta νm = FFPC sketch, spectrum and field intensity of cavity, top left insets of (c) and (d) are the enlarged field on the surface: (a) Sketch of FFPC coupling membrane; (b) Spectrum of the fundamental mode varying with cavity length, tm is 4.12 μm.

Results

Conclusion