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The optical coupling of superconducting nanowire single-photon detectors(SNSPDs) has always been restricted to a single-mode fiber for a limited detection area. In this study, for enhancing photon coupling, a dual-lens system operating at 2.2 K was used to compress the beam size on the basis of the Gaussian beam theory and geometric approximation. A magnification of approximately 0.3 was obtained, and a focused spot with diameter of approximately 10 lm was measured from a multimode fiber. Assisted with the compressed beam, a system efficiency of 55 %(1550 nm) was achieved for a SNSPD with a detection area of 10 lm 9 10 lm and 62.5 lm multimode fiber coupling. At the same time, a high speed of106 MHz was measured with the proposed system. The realization of a highly compressed optical beam reduced the optical coupling requirement and helped maintain a high speed for the SNSPD.
The optical coupling of superconducting nanowire single-photon detectors (SNSPDs) has always been restricted to a single-mode fiber for a limited detection area. In this study, for enhancing photon coupling, a dual-lens system operating at 2.2 K was used to compress the beam size on the basis of the Gaussian beam theory and geometric approximation. A magnification of approximately 0.3 was obtained, and a focused spot with diameter of approximately 10 lm was measured from a multimode fiber. Assisted with the compressed beam, a system efficiency of 55% (1550 nm) was achieved for a SNSPD with a detection area of 10 lm 9 10 lm and 62.5 lm multimode fiber coupling. At the same time, a high speed of 106 MHz was measured with the proposed system. The realization of a highly compressed optical beam reduced the optical coupling requirement and helped maintain a high speed for the SNSPD.