Stable and efficient collection of single photons emitted from a semiconductor quantum dot into a single-mode optical fiber

We study stable and efficient coupling of single photons generated from a quantum dot (QD) into a single-mode fiber (SMF) prepared in a fiber couple module (FCM). We propose a method to focus the objective lens to a sample surface without imaging with the help of laser reflection. By assembling all the constituents, i.e., a pair of lenses, the SMF, and the optical alignment to the QD source, we demonstrate stable single-photon count rate and a high collection efficiency of 43.5% of the photons emitted in air from the QD into the collection lens in the FCM