| Photonics/Optics

Compact Cooling for Superconducting Single-Photon Detectors

A new form of compact cooling technology developed for space astronomy could pave the way for use of advanced superconducting detectors for better cancer treatments, driverless cars, and practical quantum communications.

Miniaturized cooler for a fiber optic coupled superconducting detector. (Photo courtesy of University of Glasgow)

Researchers from the University of Glasgow and the STFC Rutherford Appleton Laboratory described how they have developed a supercooled detector platform capable of detecting single photons. This compact and robust platform has low enough power consumption to be used outside of a laboratory environment for the first time.

Their research builds on existing developments in extremely sensitive light sensors known as superconducting nanowire single photon detectors (SNSPDs), which are capable of detecting individual light quanta — photons — even at infrared wavelengths. The problem with SNSPDs is that they need to be cooled to just a few degrees above absolute zero (−273.15°C) in order to work effectively — a process that requires expensive and hazardous liquid helium, or a great deal of electrical power to achieve.

The team adapted a technology initially developed for the European Space Agency's Planck mission, which launched in 2009 and successfully surveyed cosmic background radiation in the microwave and infrared frequencies of the spectrum over four and a half years in space.

They used a fiber optic coupled superconducting detector supplied by the Dutch start-up Single Quantum BV and housed it in a miniaturized cooler capable of reaching temperatures of 4.2 Kelvin, or -268.95°C, which runs from standard mains power.

They've been able to use the SNSPD for infrared single-photon light detection and ranging, a form of distance measurement that could play a key role in the development of systems suitable for driverless cars in the future.

They were also able to use the system to detect infrared photons at a wavelength of 1270 nanometers, the signature of a form of excited oxygen known as singlet oxygen, which plays a key role in many biological and physiological processes.

Cancer treatment is another promising application. In a treatment called photodynamic therapy (PDT), the treatment drug exchanges energy with surrounding oxygen molecules on optical excitation, creating singlet oxygen radicals that kill tumor cells. The miniaturized cooling platform would make SNSPD use in clinical PDT much more practical, potentially making cancer treatments more effective.

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