量子点单光子源的光纤耦合

Optical fiber coupling of quantum dot single photon sources

半导体量子点在低温下产生谱线细锐的激子发光可制备单光子源.光纤耦合可避免低温共聚焦装置扫描定位和振动影响,是实现单光子源即插即用和组件化的关键技术.在耦合工艺上,基于微区定位标记发展出拉锥光纤与光子晶体腔或波导侧向耦合、大数值孔径锥形端面光纤与量子点样片垂直耦合等技术;然而,上述工艺需要多维度精密调节以避免柔软光纤的畸形弯曲实现对准和高效耦合.陶瓷插针或石英V槽封装的光纤无弯曲且具有大平滑端面,只要与单量子点样片对准贴合就可保证垂直收光, V槽封装的排式光纤还可通过盲对粘合避免扫描对准,耦合简单.本文在前期排式光纤粘合少对数分布Bragg反射镜(distributed Bragg reflector, DBR)微柱样片实现单光子输出基础上,经理论模拟采用多对数DBR腔提升样片垂直出光和光纤收光效率,使光纤输出单光子计数率大大提升.

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 lowtemperature 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 multidimensional precise adjusting in order to avoid abnormally bending a soft fiber to realize alignment and highefficiency 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 groovemounted 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 fewpair 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.