1.State Key Laborotory for Superlattices and Microsturctures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China 2.Beijing Academy of Quantum Information Sciences, Beijing 100193, China
Fund Project:Project supported by the National Key R & D Program of China (Grant Nos. 2018YFB2200504, 2018YFA0306100), the National Natural Science Foundation of China (Grant No. 61505196), and the Scientific Instrument Developing Project of Chinese Academy of Sciences, China (Grant No. YJKYYQ20170032)
Received Date:28 September 2020
Accepted Date:15 December 2020
Available Online:02 April 2021
Published Online:20 April 2021
Abstract:Semiconductor quantum dot (QD) at low temperature will create excitons with sharp spectral lines for single photon emission. Optical fiber coupling avoids scanning for positioning and vibration influence in low-temperature confocal setup, and is a key technology in realizing the plug-play and componentization of QD single photon sources. For the fiber coupling techniques, the lateral coupling of a photonic crystal cavity or waveguide with a tapered fiber, or normal coupling of a QD chip with a tapered facet fiber in a large numerical aperture has been developed based on mask in a micro-region; however, the above techniques require multi-dimensional precise adjusting in order to avoid abnormally bending a soft fiber to realize alignment and high-efficiency coupling. Ceramic ferrule or silica V-shaped groove-mounted fiber has a large smooth facet and no bending; it can collect light in the normal direction by being aligned with bonding QD chip; V-shaped groove-mounted fiber array also enables a random adhesion and avoid scanning for alignment, which is simple in technique. This work is based on the previous realization of single photon output by random adhesion of few-pair DBR micropillar chip with V-shaped groove-mounted fiber array, and uses many-pair DBR cavity chip with theoretical simulation optimization to improve the normal light extraction and its fiber collection efficiency, and greatly improves the fiber output of single photon count rate. Keywords:quantum dot single photon source/ optical fiber coupling/ distributed Bragg reflector cavity/ light normal extraction
图 4 光纤粘合SQD样品A的光谱. 分别在10和77 K下用高(红线)和低(黑线)激发功率测试; 插图: 滤光后的分束单路光谱和${g}^{2}(\tau)$及退卷积拟合(蓝线) Figure4. Sample A of fiber coupled SQD, spectra measured at 10 and 77 K under high (red) and low (black) excitation powers. Insets: One-beam spectra after filtering and ${g}^{2}(\tau)$ with deconvoluted fitting (blue).
图 5 光纤粘合SQD样品B (a)光谱(左)和${g}^{2}(\tau)$及退卷积拟合(右), 在10, 40和70 K下变激发功率测试(如蓝、红、黑线, 垂直平移以便显示; 虚线示意腔模; 虚线框示意QD1); (b)三个温度的滤光后光谱(1.1 μW激发功率测试); (c) 10 K温度下QD1的X/X*光谱双线细致结构、强度-激发功率依赖曲线, X显示劈裂, 如光谱峰拟合绿线; (d)退卷积$ {g}^{2}\left(\tau \right) $、滤光后APD实测光子计数率随激发功率的变化 Figure5. Sample B of fiber coupled SQD: (a) PL spectra (left) and ${g}^{2}(\tau)$ with deconvoluted fitting (right), measured at 10, 40 and 70 K with variable excitation power (i.e. blue, red and black, offset vertically for clarity; dash line indicates cavity mode, CM, dashed rectangular indicate QD1); (b) spectra after filtering at the three temperatures (measured under excitation power of 1.1 μW); (c) X/X* peak fine structure and intensity excitation power dependence, X shows splitting as the green spectral fittings indicate; (d) deconvoluted ${g}^{2}(\tau)$ and photon count rate at APDs after filtering, as a function of the excitation power.
样品及 温度/K
光谱峰值强度(面积)
单光子计数率
原光纤输出/s–1
滤光后 分束单路/s–1
APD两路 实测/(106 s–1)
估算原光纤 输出/(106 s–1)
${g}^{2}(0)$
净单光子 计数率/(106 s–1)
A(10)
28747(125205)
1608(9911)
0.04
1.3
0.10
1.2
A(77)
12611(626890)
922(38097)
0.13
4.3
0.05
4.1
B(10)
101360(1124015)
7491(71768)
0.32
9.2
0.70
5.0
B(40)
77800(2591945)
9305(186679)
0.88
22.0
0.70
12.0
B(70)
47840(3945870)
6479(277165)
1.10
29.0
0.70
16.0
B(70a)
15121(5604040)
10045(406237)
1.88
47.0
0.80
21.0
注: 在激发功率2.4 μW下测试, 其他未标注的为在1.1 μW下测试.
表1样品光纤输出单光子计数率汇总 Table1.Summary of fiber output single photon count rate of the samples.