Invention of the Year Nominee: A New Single-Photon Avalanche Diode System for LIDAR and Quantum Cryptography

Invention of the Year Nominee: A New Single-Photon Avalanche Diode System for LIDAR and Quantum Cryptography

Quantum communications that use single-photon detectors will soon receive a boost with a new process invented by researchers at the University of Maryland that can improve photon detection systems by making them more sensitive, one of nine nominees for the Invention of the Year Award.

“Our invention will increase the number of applications where single-photon avalanche diode (SPAD) detectors might be used,” said Senior Research Associate Alessandro Restelli of the Joint Quantum Institute.

Restelli said that the invention, when used in certain quantum processes, could help collect experimental data at a rate eight times higher and create more secret keys in a given time.

Restelli, along with National Institute of Standards and Technology (NIST) physicists Joshua C. Bianfang and Alan L. Migdall, and California Institute of Technology’s Jet Propulsion Laboratory physicist William H. Farr, developed this photon detector system.

Existing solutions to detect single photons in the near infrared region include photomultiplier tubes, superconducting nanowire single photon detectors (SNSPD), and InGaAs/InP SPADs.

SNSPDs tend to be expensive because they need very low temperatures to operate while photomultiplier tubes do not have high detection efficiency and are costly too.

“The device invented at UMD does not require high voltages or low temperature to operate and could be made at extremely low cost if they were a mainstream application,” Restelli said. “SPADs are solid state devices like the CMOS camera in everyone’s cell phone.”

The detector has broad applications in Light Detection and Ranging (LIDAR) systems where signal length is reduced to single photon levels to have control over the laser power.

“In that case, the arrival time of each individual photon with respect to the laser pulse conveys the information,” Restelli said.

“Our technique limits the fraction of time when the detector is blind, increasing the signal to noise ratio in these types of measurements, and allowing use of lower and less dangerous levels of power of the laser source,” he said.

Possible mainstream applications of LIDAR include the design of range sensors and 3D imaging systems for crash-avoidance car systems or self-driving cars.  

Restelli said that he and his research team plan to contact external companies interested in the technology once he had published the first measurements at low temperature.

“Potential end users of this device,” Restelli said, “are researchers in astronomy, quantum information, high energy particles and defense and biotechnology companies too.”

“This particular product will be of interest for users that need to operate in the near infrared region, and are interested in count/data rates of tens or hundreds of millions per second and need to localize the arrival time of a photon with a resolution around half a nanosecond,” Restelli continued. “Over time the detection system might become a general-purpose compact detection module to be embedded in a large variety of devices and experiments.”

A cryogenic system is being set up now to test the detector at low temperatures and this is proving to be quite a challenge for researchers.

Restelli said that it was possible to move around breakdown and punch through voltage by modifications in the fabrication stages of the device by changing the doping profiles.

 “In the future, a commercial product specifically designed for ’deferred multiplication‘ could be able to operate at room temperature or with an inexpensive thermoelectric cooler,” he said.

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April 23, 2015

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