Coupling light to superconductive photon counters

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.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2008

Author dc:creator

• Hu, Xiaolong

Advisor dc:contributor.advisor

• Karl K. Berggren.

• Electrical Engineering and Computer Science.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/44449

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/44449