2026-09-19T02:20:11Zhttps://dspace.mit.edu/server/oai/requestoai:dspace.mit.edu:1721.1/444492022-01-13T07:54:29Zcom_1721.1_7582com_1721.1_7581col_1721.1_131023
Karl K. Berggren.
Hu, Xiaolong
Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
2009-01-30T16:48:05Z
2009-01-30T16:48:05Z
2008
2008
http://hdl.handle.net/1721.1/44449
297117359
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.
Includes bibliographical references (p. 65-66).
Superconductive nanowire single-photon detectors (SNSPDs) are an emerging, ultrasensitive photon counting technology which may enable fiber-based, long-haul quantum key distribution. Our group has successfully developed a robust process to fabricate SNSPDs, and has demonstrated device-detection-efficiency above 50% at near infrared wavelengths. However, one remaining challenge must be taken - efficiently coupling light into the detector. This step is difficult because of the small active area of the SNSPD and its low temperature operation. In this thesis, I have designed two experimental setups to couple the light from fiber to the detector at a cryogenic temperature of 4 K: one is for immersion device-testing in a dewar; another is for packaging the detector inside a cryocooler. In addition, I have designed and fabricated SNSPDs suitable for the coupling with single-mode fiber, based on my theoretical calculation of the system detection-efficiency. Some important parameters to characterize the detectors such as system-detection-efficiency, dark-count rate, and counting rate vs. optical input power have been measured.
by Xiaolong Hu.
S.M.
66 p.
eng
Massachusetts Institute of Technology
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http://dspace.mit.edu/handle/1721.1/7582
Electrical Engineering and Computer Science.
Coupling light to superconductive photon counters
Thesis
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<Abstract>Superconductive nanowire single-photon detectors (SNSPDs) are an emerging, ultrasensitive photon counting technology which may enable fiber-based, long-haul quantum key distribution. Our group has successfully developed a robust process to fabricate SNSPDs, and has demonstrated device-detection-efficiency above 50% at near infrared wavelengths. However, one remaining challenge must be taken - efficiently coupling light into the detector. This step is difficult because of the small active area of the SNSPD and its low temperature operation. In this thesis, I have designed two experimental setups to couple the light from fiber to the detector at a cryogenic temperature of 4 K: one is for immersion device-testing in a dewar; another is for packaging the detector inside a cryocooler. In addition, I have designed and fabricated SNSPDs suitable for the coupling with single-mode fiber, based on my theoretical calculation of the system detection-efficiency. Some important parameters to characterize the detectors such as system-detection-efficiency, dark-count rate, and counting rate vs. optical input power have been measured.</Abstract>
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